# High-Resolution Near-infrared Spectroscopy of Diffuse Sources around MWC
1080

Il-Joong Kim11affiliation: Korea Astronomy and Space Science Institute,
Daejeon, 34055, Republic of Korea<EMAIL_ADDRESS>Heeyoung Oh11affiliation:
Korea Astronomy and Space Science Institute, Daejeon, 34055, Republic of
Korea<EMAIL_ADDRESS>Woong-Seob Jeong11affiliation: Korea Astronomy and
Space Science Institute, Daejeon, 34055, Republic of Korea<EMAIL_ADDRESS>22affiliation: Astronomy and Space Science Major, University of Science and
Technology, Daejeon, 34113, Republic of Korea Kwang-Il Seon11affiliation:
Korea Astronomy and Space Science Institute, Daejeon, 34055, Republic of
Korea<EMAIL_ADDRESS>22affiliation: Astronomy and Space Science Major,
University of Science and Technology, Daejeon, 34113, Republic of Korea Tae-
Soo Pyo33affiliation: Subaru Telescope, National Astronomical Observatory of
Japan, National Institutes of Natural Sciences (NINS), 650 North A’ohoku
Place, Hilo, HI 96720, USA 44affiliation: School of Mathematical and Physical
Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama,
Kanagawa 240-0193, Japan Jae-Joon Lee11affiliation: Korea Astronomy and Space
Science Institute, Daejeon, 34055, Republic of Korea<EMAIL_ADDRESS>
###### Abstract

To reveal the origins of diffuse H$\alpha$ emissions observed around the
Herbig star MWC 1080, we have performed a high-resolution near-infrared (NIR)
spectroscopic observation using the Immersion GRating INfrared Spectrograph
(IGRINS). In the NIR H and K bands, we detected various emission lines (six
hydrogen Brackett lines, seven H2 lines, and an [Fe II] line) and compared
their spatial locations with the optical (H$\alpha$ and [S II]) and radio
(13CO and CS) line maps. The shock-induced H2 and [Fe II] lines indicate the
presence of multiple outflows, consisting of at least three, associated young
stars in this region. The kinematics of H2 and [Fe II] near the northeast (NE)
cavity edge supports that the NE main outflow from MWC 1080A is the
blueshifted one with a low inclination angle. The H2 and [Fe II] lines near
the southeast molecular region newly reveal that additional highly-blueshifted
outflows originate from other young stars. The fluorescent H2 lines were found
to trace photodissociation regions formed on the cylindrical surfaces of the
main outflow cavity, which are expanding outward with a velocity of about
10–15 km s-1. For the H$\alpha$ emission, we identify its components
associated with two stellar outflows and two young stars in addition to the
dominant component of MWC 1080A scattered by dust. We also report a few faint
H$\alpha$ features located $\sim$0.4 pc away in the southwest direction from
MWC 1080A, which lie near the axes of the NE main outflow and one of the
newly-identified outflows.

###### Subject headings:

infrared: ISM — ISM: Herbig-Haro objects — ISM: jets and outflows — ISM:
molecules — stars: formation — stars: individual (MWC 1080) — techniques:
spectroscopic

##  I. Introduction

The MIRIS Pa$\alpha$ Galactic Plane Survey detected a lot of new
Pa$\alpha$-emitting sources (Kim et al., 2018), which are expected to be
associated with star-forming activities in our Galaxy. The Pa$\alpha$ sources
would give important clues to understand the star forming history of our
Galaxy. In the Cepheus region, we found 127 Pa$\alpha$ sources (109 extended
sources and 18 point-like sources). The extended Pa$\alpha$ sources are mostly
H II regions, while the point-like sources are planetary nebulae or emission-
line stars, such as Wolf-Rayet and Herbig Ae/Be stars. For three sources among
the point-like Pa$\alpha$ sources, we also found diffuse extended H$\alpha$
features surrounding H$\alpha$ point sources using the INT/WFC Photometric
H$\alpha$ Survey (IPHAS) data with a higher spatial resolution. The nebulosity
surrounding stars would be caused by the leftover material and partially
ionized gas ejected by stars in the process of star formation, colliding with
nearby clouds of gas and dust. The extended H$\alpha$ emission originates from
recombination in ionized gas or the dust scattering of stellar photons, or
both. However, it is not clear which mechanism (ionized gas or dust
scattering) is more plausible in many cases. To better understand the origin
of the extended H$\alpha$ emission around the emission-line stars (shown as
point-like Pa$\alpha$ sources by MIRIS), we have carried out high-resolution
near-infrared (NIR) spectroscopic follow-up observations toward them.

MWC 1080, the first follow-up target, is one of the brightest Pa$\alpha$
sources detected in Cepheus through the survey. MWC 1080 is known to be a
Herbig Ae/Be star with a B0 spectral type according to the SIMBAD database.
Cantó et al. (1984) suggested a kinematic distance of 2.5 kpc based on the
13CO emission from the parent cloud. On the other hand, Hillenbrand et al.
(1992) and Fuente et al. (2003) applied a distance of 1 kpc to circumstellar
disks around MWC 1080. Its parallax distance has been recently measured to be
1.373 $\pm$ 0.174 kpc (Gaia Collaboration, 2018). MWC 1080 is, in fact, a
multiple system consisting of a primary star (MWC 1080A), a close
(0.$\arcsec$8) companion (MWC 1080B), and a third companion (MWC 1080E)
located $\sim$5.$\arcsec$2 east from MWC 1080A (Leinert et al., 1997; Polomski
et al., 2002). Leinert et al. (1997) classified MWC 1080B as another Herbig
Ae/Be star.

Kim et al. (2018) proposed that the extended H$\alpha$ features around MWC
1080 might be a young H II region. The previous studies for MWC 1080, however,
are likely to suggest that the extended H$\alpha$ features are not a simple H
II region. Diffuse sources around MWC 1080 have been observed at various
wavelengths since Herbig (1960) included MWC 1080 in his list of stars with
nebulosity. Yoshida et al. (1992) performed optical spectroscopic observations
of the primary star MWC 1080A and its associated nebulosity, and found the
existence of a strong H$\alpha$ emission line in the optical spectrum of MWC
1080A, but no evidence of shock or ultraviolet (UV) excitation in the nebular
spectra. They concluded, based on the existence of the H$\alpha$ recombination
lines and the absence of any forbidden line, that the extended H$\alpha$
features are attributable to scattering of the stellar H$\alpha$ line from MWC
1080A by dusty materials rather than an ionized medium, as in bright
reflection nebulae observed at the optical and infrared (IR) wavelengths. On
the other hand, the existence of the main outflow cavity discovered later by
Wang et al. (2008) and the [S II] Herbig-Haro (HH) objects by Poetzel et al.
(1992) supports the possibility that, at least, some portions of the extended
H$\alpha$ emission are caused by outflows from MWC 1080A and/or other young
stars. Because no strong [S II] forbidden line was detected in the stellar
spectrum of MWC 1080A (Yoshida et al., 1992), the [S II] HH objects are likely
caused by shock excitation. Curiel et al. (1989) reported weak extended 6-cm
radio continuums, which come from ionized gas, in association with MWC 1080.
Sandell et al. (2011) presented the 850 $\micron$ dust continuum, of which the
morphology seems to be similar to that of the 6-cm radio continuum. This
similarity in morphology suggests that the 850 $\micron$ continuum originates
from warm dust in the ionized gas. Harvey et al. (1979) also presented
evidence for thermal emissions from circumstellar dust, leftover from the star
formation process, by far-IR (40–160 $\micron$) observations. Fuente et al.
(2003) and Alonso-Albi et al. (2009) studied millimeter continuum images to
find evidence for a circumstellar disk around MWC 1080. Alonso-Albi et al.
(2009) found several clumps in their 1.3 and 2.7 mm images and proposed, based
on the millimeter morphology and spectral energy distribution (SED) from the
NIR to the centimeter wavelengths, that the clumps can be a compact disk close
to MWC 1080 plus a large toroidal envelope with an inner radius of 6000 AU.
Girart et al. (2002) detected three resolved radio continuum sources around
MWC 1080 using the Very Large Array (VLA) observations at 6 cm. The central
source (VLA 4) among the three sources seems to coincide with MWC 1080A (see
Figure 26 of Sandell et al. (2011)). Girart et al. (2002) suggested that the
other two VLA sources may trace embedded young stellar objects (YSOs).

Poetzel et al. (1992) reported the discovery of HH objects associated with MWC
1080 in a continuum-subtracted [S II] $\lambda$6730Å image. They suggested the
direction of the bipolar outflow from MWC 1080A to have position angles (PAs)
of $\simeq$ 60$\arcdeg$ and 240$\arcdeg$ (east from the north) and interpreted
all of the HH objects as the rim-brightened edges of the outflow cavity.
However, Wang et al. (2008) found that the bipolar outflow cavity has PAs of
$\simeq$ 45$\arcdeg$ and 225$\arcdeg$ using molecular maps. They investigated
the morphologies of the molecular clouds around MWC 1080 by observing the
CS($J$ = 2 $\rightarrow$ 1), 13CO($J$ = 1 $\rightarrow$ 0), and C18O($J$ = 1
$\rightarrow$ 0) lines and identified a cavity elongated along the northeast
(NE)-southwest (SW) direction. Particularly, the 13CO map revealed an almost
perfect biconical cavity. They noticed that the size of the cavity is much
smaller than those in older Herbig Ae/Be star systems and suggested that a
previous bipolar outflow from MWC 1080 (hereafter main outflow) has formed the
cavity, and the main outflow may be still active. Wang et al. (2008) also
presented a NIR $K^{\prime}$-band image with $\sim$0.$\arcsec$1 resolution,
which shows $\sim$50 young, low-mass stars and a reflection nebula with an
hourglass shape in the direction perpendicular to the main outflow axis.
Because most of the young stars are located inside the main outflow cavity,
Wang et al. (2008) suggested that they were likely formed together with MWC
1080 and then have been exposed to the cavity. Recently, Li et al. (2014)
obtained mid-IR (11.2, 11.6, and 18.5 $\micron$) images for the MWC 1080
region with a sub-arcsecond resolution. They demonstrated that the diffuse
mid-IR emissions observed around MWC 1080 trace neither a disk nor an
envelope, but the internal surfaces of the main outflow cavity revealed by the
13CO map. Hence, they concluded that the observed mid-IR emission would
originate from warm dust grains, heated by the stellar radiation, located
close to the main outflow cavity walls.

This paper presents the results of a high-resolution NIR spectroscopic
observation for the MWC 1080 region using the Immersion GRating INfrared
Spectrograph (IGRINS). This is the first high-resolution NIR spectroscopy for
this region. Because IGRINS has a broad wavelength coverage of the whole H and
K bands, we expect to detect various hydrogen Brackett lines related to the
Pa$\alpha$ and H$\alpha$ emissions, which would enable us to reveal the origin
of the hydrogen recombination line emissions. Also, IGRINS has detected the H2
and [Fe II] lines induced by stellar outflows (e.g., Oh et al., 2016a, b),
which provides an opportunity to find stellar outflows in this region. Section
II describes the IGRINS NIR spectroscopy and the IPHAS H$\alpha$ data
acquisition. In Section III, we present the results of the IGRINS
spectroscopy. We report diffuse sources identified in the position-velocity
diagrams (PVDs) of the observed emission lines, and measure the line profiles
and line fluxes for the individual sources. Also, we classify the diffuse
sources into several types according to their origins revealed from the
spectroscopic analysis and the spatial correlations with the H$\alpha$, [S
II], and 13CO maps. In Section IV, we discuss the stellar outflows identified
in this study and the possible origins of the atomic hydrogen line emission
extended widely in the MWC 1080 region. We also discuss the plausible origins
of the compact hydrogen line emission detected in three young stars. Finally,
Section V contains the summary and conclusions of our main results.

##  II. Observations and Data Acquisition

###  II.1. IGRINS NIR Spectroscopy

Figure 1.— (a) IGRINS slit positions (blue 9.$\arcsec$3 $\times$ 0.$\arcsec$63
rectangles) overlaid on the 13CO contour map, and (b) IPHAS H$\alpha$ image
(continuum-subtracted) of the whole MWC 1080 region. In panel (a), the 13CO
map was adapted from Figure 2 of Wang et al. (2008), and its beam size is
shown in the lower right corner of the figure. Triangles indicate the NIR-
identified young, low-mass stars (Wang et al., 2008), out of which seven stars
are also denoted in red dashed circles. The red diagonal line passing through
MWC 1080A at PA = 40$\arcdeg$ is the central axis of the main outflow cavity.
In panel (b), the circle with a radius of 1$\arcmin$ represents the whole area
of the H$\alpha$ features detected in this paper, and the dashed square
indicates the area displayed in (a). The blue+red line, representing the main
outflow, with PA = 40$\arcdeg$ is the same as the diagonal line in (a). The
blue and red colors indicate the blueshifted and redshifted parts of the
bipolar outflow, respectively (see Section IV.1.1). The two blue+red lines
with PA = 135 and 77$\arcdeg$ represent the outflows newly-identified in this
study (“Outflow A” and “Outflow B”), which are discussed in Section IV.1.2.
The two white dashed circles indicate faint H$\alpha$ features related to the
main outflow and “Outflow B.” The small bent line, shown in both (a) and (b),
denotes an arc-like H$\alpha$ feature located on the axis of the main outflow.

IGRINS is a cross-dispersed NIR spectrograph equipped with a silicon immersion
grating. With a spectral resolution of $\lambda$/$\Delta\lambda$ $\sim$45,000
(corresponding to a velocity resolution of 7.5 km s-1), it covers the H-band
(1.49–1.80 $\micron$) and K-band (1.96–2.46 $\micron$) wavelength ranges
simultaneously (Yuk et al., 2010; Park et al., 2014; Mace et al., 2018). We
carried out the IGRINS observations of the MWC 1080 region on 2017 November
26–28 and December 28 using the 4.3 m Lowell Discovery Telescope in Arizona.
The IGRINS slit size corresponds to a field of view of 0.$\arcsec$63 $\times$
9.$\arcsec$3 on the sky when it is mounted on the 4.3 m telescope. We observed
a total of ten slit positions on the first observation date (November 26) with
a seeing FWHM of $\sim$0.$\arcsec$6 in the K band, which are indicated by blue
rectangles in Figure 1(a). Slit positions S1–S6 were set to be in the
northwest (NW)-southeast (SE) direction (PA = 130$\arcdeg$), which is
perpendicular to the axis of the main outflow cavity observed in the 13CO map.
On the other hand, slit positions S7–S10 were aligned parallel to the cavity
axis (PA = 40$\arcdeg$). In the figure, the triangles indicate the NIR-
identified young, low-mass stars presented by Wang et al. (2008). We also
denote the locations of seven young stars (YSO 1, YSO 2, YSO 3, YSO 4, MWC
1080E, and MWC 1080A+B), which are relevant in this paper, in red dashed
circles. Although we additionally observed twelve slit positions in the SE
molecular region for the other three observation dates (November 27–28 and
December 28), we used this data only for velocity channel maps in the Appendix
because of bad weather conditions.

We took the off-source exposures between every on-source exposure to subtract
backgrounds such as the telluric emission, bias signal, dark current, etc. The
off-source position was chosen to be $\sim$2$\arcmin$ north from each on-
source position. The total on-source exposure time for each slit position was
10 minutes (two 5-minute exposures) for S1–S8 and 20 minutes (four 5-minute
exposures) for S9 and S10. Auto-guiding was performed with the K-band slit-
viewing camera, which covers a $\sim$1.$\arcmin$3 $\times$ 2$\arcmin$ field,
including the slit position, during the observation. We selected a nearby
bright star (YSO 3 in Figure 1(a)) as a guiding star. The slit-viewing image
taken during the observation was also used to check the planned slit position.
We measured dark and flat-field calibration frames at the beginning of each
night and observed an A0V-type star HD 223386 as a telluric standard star. To
obtain the stellar spectrum of the central, bright star MWC 1080A, we also
observed it four times with a 15-second exposure on the first observation
date.

Basic data reduction was carried out using the IGRINS Pipeline
Package111https://github.com/igrins/plp (PLP, Lee et al., 2017), which can
deal with the removal of bad pixels and cosmic rays, flat fielding, sky
subtraction, spectral extraction, and wavelength calibration. The PLP provides
signal and variance ($\sigma^{2}$) values for the processed spectra. We also
utilized the python software “Plotspec”222https://github.com/kfkaplan/plotspec
designed for analyzing two-dimensional IGRINS spectra of extended sources. It
is capable of performing the telluric correction, relative flux calibration,
continuum subtraction, etc. (Kaplan et al., 2017). Using the software, we
constructed two data cubes for every detected emission line in the sky field
including all slit positions. One is a continuum-subtracted data cube, which
was used to make velocity-integrated maps and PVDs for each emission line. The
other is a data cube that contains continuum signals, which was used to
measure spectral line profiles for the individual targets. The data cubes have
three axes of right ascension (RA), declination (DEC), and radial velocity
($V$). Here, $V$ was adjusted to represent the relative radial velocity with
respect to the systemic local standard of rest (LSR) velocity of the MWC 1080
system. The adopted systemic LSR velocity is $-$30 km s-1, measured from the
12CO observation by Wouterloot & Brand (1989). We note that the above data
reduction method could not completely remove the telluric OH lines because of
the time-variability of the line fluxes. Therefore, we manually confirmed that
the residual OH lines did not severely contaminate any spectroscopic results
presented in this paper. We assumed that the residual fluxes measured at the
OH line wavelength, given in Rousselot et al. (2000), are uniform along the
spatial direction of the slit. Some strong residuals were masked out when we
measured the line profiles.

###  II.2. IPHAS H$\alpha$ Data

We obtained the continuum-subtracted H$\alpha$ image for the MWC 1080 region
from the calibrated IPHAS data (Barentsen et al., 2014). We used the same
method as described in Kim et al. (2018), except that we retained the original
pixel size ($\sim$0.$\arcsec$33) of the IPHAS data. For the narrow-band
H$\alpha$ and broad-band $r$ filters, we extracted a total of three IPHAS
field data covering the MWC 1080 region with an angular size of 3$\arcmin$
$\times$ 3$\arcmin$. We confirmed that the data satisfy the IPHAS data quality
criteria (Barentsen et al., 2014). In addition, the pixels with a “confidence”
value $<$70 in the “confidence” map for each IPHAS field data (González-
Solares et al., 2008) were masked out. Using the photometric zero points and
zero magnitudes for the IPHAS H$\alpha$ and $r$ filters, the pixel values were
transformed into calibrated flux units of W m-2 Å-1 arcsec-2. To match the sky
background levels among the individual field images, we subtracted the median
background from each field image. All field images in each band were then
combined into a single mosaic image using the Montage software.

Because the wavelength range of the broad-band $r$ filter entirely includes
that of the narrow-band H$\alpha$ filter (Drew et al., 2005), we multiplied
the H$\alpha$ filter image minus the $r$ filter image by a correction factor
of $(\Sigma T_{H\alpha}\times\Sigma T_{r})/(\Sigma T_{r}-\Sigma T_{H\alpha})$,
where $\Sigma T_{H\alpha}$ and $\Sigma T_{r}$ are the integrals of the
H$\alpha$\- and $r$-filter transmission curves over the wavelength,
respectively. This factor prevents the continuum-subtracted H$\alpha$ image
from over-subtracting the background continuum, which can arise in a simple-
subtraction procedure. It also converts the pixel unit of the continuum-
subtracted H$\alpha$ image into the in-band flux unit of W m-2 arcsec-2. We
note that this IPHAS H$\alpha$ flux can include some contributions from the [N
II] $\lambda\lambda$6548, 6584 Å lines, which are contained within the IPHAS
H$\alpha$ filter. Figure 1(b) shows the resulting continuum-subtracted
H$\alpha$ mosaic image of the MWC 1080 region. The region close to MWC 1080A
is saturated in the IPHAS H$\alpha$\- and $r$-filter images, and thus it was
masked out. Also, there remained imaging artifacts near other bright stars
after the continuum subtraction, which is probably due to the difference of
the point-spread function (PSF) between the H$\alpha$ and $r$ bands. Although
the PSF sizes measured in the H$\alpha$\- and $r$-filter images were similar
(FWHM $\sim$1.$\arcsec$2 and $\sim$1.$\arcsec$3, respectively), the PSF
matching was not accomplished well. Therefore, we masked out one more bright
star (YSO 4), showing strong artifacts in the central region of the figure. We
note, however, that our analysis on the extended sources was hardly affected
by the PSF difference.

In Figure 1(b), the H$\alpha$ emission is found to extend out to at least
$\sim$1$\arcmin$ from MWC 1080A, as indicated by a solid circle. This radius
corresponds to $\sim$0.4 pc at the parallax distance of MWC 1080 (1.373 $\pm$
0.174 kpc, Gaia Collaboration, 2018). We found that an arc-like H$\alpha$
feature lies on the approximate axis of the main outflow cavity, as shown by a
red bent line in the figure. As can be seen in Figure 1(a), this H$\alpha$
feature is well coincident with the 13CO boundary forming the NE edge of the
main outflow cavity. The diagonal red line passing through MWC 1080A with PA =
40$\arcdeg$ passes the apex of the arc-like H$\alpha$ feature almost exactly.
We also identified a few faint H$\alpha$ features far away in the SW direction
from MWC 1080A. In Figure 1(b), they are distributed between (RA, DEC) $\sim$
(23h17m24s, +60$\arcdeg$49$\arcmin$50$\arcsec$) and (RA, DEC) $\sim$
(23h17m18s, +60$\arcdeg$50$\arcmin$35$\arcsec$), two of which are indicated by
the white dashed circles. In the figure, the blue+red line representing the
main outflow is the same as the diagonal red line in Figure 1(a); here, the
blue and red colors indicate the blueshifted and redshifted parts of the
bipolar outflow, respectively, which will be discussed in Section IV.1.1. We
also overlaid two additional blue+red lines with PA = 135 and 77$\arcdeg$ that
represent two outflows newly-identified in this study, “Outflow A” and
“Outflow B,” respectively. We will discuss these outflows in Section IV.1.2.

##  III. Results

###  III.1. Hydrogen Brackett Lines

Figure 2.— (a) Continuum-subtracted Br$\gamma$ map integrated over $-$200 km
s-1 $\leq$ $V$ $\leq$ +200 km s-1, and PVDs for (b) the NW-SE slits S1–S6 and
(c) NE-SW slits S7–S10. The color scales are all in units of the detection
significance (signal/$\sigma$). In panel (a), the overlaid 13CO contours,
triangles, red dashed circles (young stars), red diagonal line (axis of the
main outflow cavity), and red bent line (arc-like H$\alpha$ feature) are the
same as in Figure 1(a). The magenta diagonal dashed line is another possible
axis of the main outflow cavity (see Section III.1.1). In panels (b) and (c),
the origin of the NW-SE offset X and NE-SW offset Y is the position of MWC
1080A; their positive directions are indicated in (a). The contours on the
PVDs represent a significance level of 3$\sigma$. Seven Br$\gamma$ sources
identified in this study are also denoted, together with the vertical solid
lines that represent the spatial extent, in the PVDs. The vertical dashed
lines indicate the X and Y positions of the young stars denoted in (a). Figure
3.— Br$\gamma$ line profiles for the diffuse sources, integrated over the
source region that is bounded by the vertical solid lines in Figures 2(b) and
(c). The line profile for the star MWC 1080A is also shown for comparison.
Each line profile was fitted with a Gaussian function plus a linear continuum
(For Br YSO 1, we used two Gaussian functions), and the resulting linear
continuum was subtracted from the line profile. The best-fit Gaussian function
is shown in blue (negative centroid velocity or blueshift) or red (positive
centroid velocity or redshift). The best-fit result obtained from two
Gaussians for Br YSO 1 is also overplotted with the green curve. The centroid
velocity $V_{\mathrm{centroid}}$, FWHM velocity width $\Delta V$, and line
flux $F_{0}$ obtained from the fitting are shown in each panel and also listed
in Table 1. The green dotted lines indicate the positions of the telluric OH
lines (Rousselot et al., 2000). There are no telluric residuals that severely
contaminate the Br$\gamma$ line profiles. The instrumental profiles ($\Delta
V$ $\simeq$ 6.5 km s-1 estimated from telluric OH lines) have not been removed
from the line profiles, which gives only a difference of $<$1 km s-1 for
$\Delta V$ $>$ 20 km s-1.

We detected six hydrogen Brackett lines (Br$\gamma$, 10, 11, 12, 13, and 14)
from the diffuse sources around MWC 1080 using IGRINS. Figure 2(a) shows the
continuum-subtracted Br$\gamma$ map integrated over $-$200 km s-1 $\leq$ $V$
$\leq$ +200 km s-1. The X and Y axes in the figure denote the spatial
direction in the PDVs for slits S1–S6 and S7–S10, respectively. We note that
the slit directions (and thus the X and Y directions) are perpendicular or
parallel to the axis of the main outflow cavity. The origin of the X and Y
offsets was set to be the position of MWC 1080A. Following the definition, the
Br$\gamma$ PVDs are shown for the slit positions S1–S10 in Figures 2(b) and
(c). A total of seven Br$\gamma$ sources (5 extended sources and 2 compact
sources) are identified in the PVDs. In the figure, the source identification
names are also shown together with the vertical boundary lines, indicating the
spatial extents of the sources. Five of the Br$\gamma$ sources are widely
extended around MWC 1080A. They are referred to as Br SW, Br NW, Br SE, Br NE
1, and Br NE 2 according to their positions relative to MWC 1080A. The
extended feature found in S7 is identical to Br SE in S3, and thus, its
identification name was not denoted in S7 for clarity. Two of the Br$\gamma$
sources are relatively compact and confined within small areas close to the
young stars MWC 1080E and YSO 1; they are referred to as Br 1080E and Br YSO
1, respectively.

To measure the Br$\gamma$ line profiles for the Br$\gamma$ sources, we
integrated the cube data over the spatial axis that is bounded by the vertical
solid lines in Figures 2(b) and (c). The resulting Br$\gamma$ line profiles
are shown in Figure 3. We fitted the individual line profiles with a Gaussian
function plus a linear continuum and measured the centroid velocity
$V_{\mathrm{centroid}}$, FWHM velocity width $\Delta V$, and line flux
$F_{0}$. Regarding Br YSO 1, two Gaussian functions were applied to resolve
the emission and absorption components. The best-fit results are presented in
each panel of Figure 3 and also listed in the first row of Table 1. In Figure
3, we also plot the Br$\gamma$ line profile obtained from the observation of
the stellar source MWC 1080A. Because the Br$\gamma$ profile for MWC 1080A has
a broad redshifted wing extending up to $\sim$300 km s-1, the best-fit
Gaussian function shows a slight disagreement with the actual line profile.
However, the best-fit parameters $V_{\mathrm{centroid}}$ = $-$8 km s-1 and
$\Delta V$ = 163 km s-1 appear to provide moderate estimates for the centroid
velocity and velocity width of the Br$\gamma$ line profile. All of the
Br$\gamma$ sources show broad ($\Delta V$ $>$ 150 km s-1) and generally
symmetric line profiles except Br YSO 1.

For the Br$\gamma$ sources, the other Brackett lines (Br 10 to Br 14) were
also analyzed by the same method as applied to Br$\gamma$. Some strong
telluric OH residuals found near the Br 10, Br 12, Br 13, and Br 14 lines were
masked out before the line profiles were measured. The results for the lines
with the fluxes measured at a significance level of $\geq$3$\sigma$ are shown
in Table 1. For Br YSO 1, no Br 10–14 lines were detected with $\geq$3$\sigma$
significance. The best-fit parameters $V_{\mathrm{centroid}}$ and $\Delta V$
for the Br 10–14 lines were found to be slightly different from those for
Br$\gamma$. However, the Br 10–14 line profiles are also broad ($\Delta V$ $>$
100 km s-1) and nearly symmetric, except for MWC 1080A, as found in
Br$\gamma$. For the star MWC 1080A, the Br 10–14 line profiles were found to
be broad, but show redshifted wing features, as in Br$\gamma$; hence, the
estimated $V_{\mathrm{centroid}}$, $\Delta V$, and line flux $F$ of Br 10–14
for MWC 1080A are less reliable.

####  III.1.1 Direct and Scattered Br$\gamma$ Sources

Figure 4.— (a) Br 10 / Br$\gamma$ vs. Br 11 / Br$\gamma$ line ratio diagram
for the Br$\gamma$ sources and MWC 1080A, and (b) the Br$\gamma$ map overlaid
on the H$\alpha$ contours. In panel (a), the observed line ratios (with
1$\sigma$ error bars) were calculated from the normalized line fluxes
$F/F_{0}$ in Table 1. The green open circles indicate the line ratios
reddening-corrected assuming $A_{V}$ = 5 mag. The dotted, solid, and dashed
lines represent the theoretical ratios of the hydrogen recombination lines
(Case B approximation, Storey & Hummer, 1995). In panel (b), the Br$\gamma$
map is the same as in Figure 2(a), and the seven Br$\gamma$ sources identified
in the PVDs (Figures 2(b) and (c)) are indicated by their assigned names. The
H$\alpha$ contours were obtained from Figure 1(b). The contour levels are 8,
12, 30, 50, 100, 150, 200, and 250 $\times$ 10-19 W m-2 arcsec-2. Red dashed
circles (young stars), a red diagonal line (axis of the main outflow cavity),
and a red bent line (arc-like H$\alpha$ feature) are the same as in Figure
1(a).

As described in Section III.1, seven Br$\gamma$ sources were identified from
the PVDs (Figure 2). We now classify them according to their origins in two
groups: direct Br$\gamma$ sources and scattered ones. Five of them (Br SW, Br
NW, Br SE, Br NE 1, and Br NE 2) are spatially extended sources, and two of
them (Br 1080E and Br YSO 1) are point-like, compact sources. We note that the
compact sources Br 1080E and Br YSO 1 were found to be spatially coincident
with the stars MWC 1080E and YSO 1, respectively, and thus, their
identification names were given following the corresponding stars. Figure 3
shows the Br$\gamma$ line profiles, which are all broad ($\Delta V$ $>$ 150 km
s-1) and generally symmetric about the line center except Br YSO 1. The best-
fit results of the Gaussian-line fitting for the line profiles show that the
extended Br$\gamma$ sources (Br SW, Br NW, Br SE, Br NE 1, and Br NE 2) have
negative centroid velocities of $V_{\mathrm{centroid}}$ = $-$11 to $-$2 km s-1
and relatively narrow velocity widths of $\Delta V$ = 151 to 171 km s-1.
However, the compact source Br 1080E has a positive $V_{\mathrm{centroid}}$ =
+8 km s-1 and broader $\Delta V$ = 235 km s-1. The difference of the velocity
widths between Br 1080E and the extended sources is also shown clearly in the
Br$\gamma$ PVDs (see Figure 2). In Figure 3, the Br$\gamma$ line profile of
the other compact source Br YSO 1 was fitted with two Gaussians that represent
the emission and absorption components, respectively. The best-fit parameters
for the emission component were obtained to be $V_{\mathrm{centroid}}$ = $-$11
km s-1 and $\Delta V$ = 234 km s-1. This result indicates that the Br$\gamma$
emission line profile of Br YSO 1 is also distinct from those of the extended
Br$\gamma$ sources: a similar $V_{\mathrm{centroid}}$, but a much broader
$\Delta V$. In Figure 3, the Br$\gamma$ line profile for the star MWC 1080A
shows $V_{\mathrm{centroid}}$ = $-$8 km s-1 and $\Delta V$ = 163 km s-1, which
is similar to those obtained from the extended Br$\gamma$ sources. The
estimated best-fit parameters are slightly inconsistent (differences of $<$9
km s-1 for $V_{\mathrm{centroid}}$ and $<$20 km s-1 for $\Delta V$) due to the
broad wing component; however, the shapes of the line profiles agree well with
each other. The similarity in the Br$\gamma$ line profiles between the central
star MWC 1080A and the extended sources implies that the extended sources (Br
SW, Br NW, Br SE, Br NE 1, and Br NE 2) would be dusty reflection nebulae that
scatter the stellar Br$\gamma$ emission from MWC 1080A. On the other hand, the
compact sources Br 1080E and Br YSO 1 are most likely to be direct emissions
from the young stars MWC 1080E and YSO 1, respectively.

In Figure 4(a), we compare the line ratios Br 10/Br$\gamma$ and Br
11/Br$\gamma$ for six Br$\gamma$ sources and the star MWC 1080A, from which
both the Br 10 and Br 11 lines were significantly detected at a level of
$>$10$\sigma$. We used the normalized line fluxes $F/F_{0}$ for Br 10 and Br
11 presented in Table 1. In the figure, we also show the ratios reddening-
corrected by assuming $A_{V}$ = 5 mag and utilizing the extinction curve of
Cardelli et al. (1989) with $R_{V}$ = 3.1. Figure 4(a) also shows the
theoretical line ratios calculated assuming the Case B recombination (Storey &
Hummer, 1995) for a combination of two temperatures of $T_{\mathrm{e}}$ =
5$\times$102 K (blue) and 104 K (red) and three density ranges of
$N_{\mathrm{e}}$ = 102–105 cm-3 (dotted), 105–108 cm-3 (solid), and 108–1010
cm-3 (dashed). We also calculated the theoretical line ratios for a wide range
of electron temperature $T_{\mathrm{e}}$ = 5$\times$102–105 K and electron
density $N_{\mathrm{e}}$ = 102–1014 cm-3, but they are not shown in the
figure.

Figure 4(a) shows that all the line ratios measured for the extended
Br$\gamma$ sources (Br SW, Br NW, Br SE, Br NE 1, and Br NE 2) are higher than
those for the star MWC 1080A. We note that the line ratios for MWC 1080A could
be affected by the broad wing components, as mentioned in Section III.1.
However, we also found that the line ratios for the extended sources are
higher than those theoretically-predicted for most of $T_{\mathrm{e}}$ and
$N_{\mathrm{e}}$; the line ratios are found to be comparable only with the
predictions for the lowest temperature $T_{\mathrm{e}}$ = 5$\times$102 K and
the highest density $N_{\mathrm{e}}$ = 108–1010 cm-3. Moreover, even this
extreme case was not able to reproduce the observed line ratios if the dust
extinction toward the sources is higher than $A_{V}$ = 5 mag (see the green
open circles in the figures). The excess of the line ratios (Br 10/Br$\gamma$
and Br 11/Br$\gamma)$ strongly supports our conclusion, inferred from the line
profiles, that the extended Br$\gamma$ sources are dusty nebulae illuminated
by MWC 1080A. The lines Br 10 and Br 11 have shorter wavelengths than
Br$\gamma$ and thus are more easily scattered by dust. The scattered light in
the Br 10 and Br 11 lines then gives higher line ratios than those
theoretically-predicted for the intrinsic line ratios of the direct light from
MWC 1080A. In contrast, the line ratios for the compact source Br 1080E were
found to be much lower than those for the extended sources and MWC 1080A. They
are also lower than those predicted for most combinations of $T_{\mathrm{e}}$
and $N_{\mathrm{e}}$ except for the extreme case of $T_{\mathrm{e}}$ =
5$\times$102 K and $N_{\mathrm{e}}$ = 102–105 cm-3. This result supports that
the compact source Br 1080E, which is spatially coincident with MWC 1080E, is
most likely a direct emission from MWC 1080E. Because no scattered light will
contribute to the point-like source, Br 10 and Br 11 are attenuated more
strongly than Br$\gamma$. This makes the observed line ratios of Br
10/Br$\gamma$ and Br 11/Br$\gamma$ for Br 1080E much lower than the intrinsic
line ratios. Hence, we can estimate the extinction $A_{V}$ toward MWC 1080E by
assuming Case B and, for instance, $T_{\mathrm{e}}$ = 104 K and
$N_{\mathrm{e}}$ = 106 cm-3. The extinction $A_{V}$ toward MWC 1080E is then
derived as 4.0 $\pm$ 1.8 mag from Br 10/Br$\gamma$ and 6.9 $\pm$ 1.4 mag from
Br 11/Br$\gamma$. These values are comparable with $A_{V}$ $\simeq$ 5 mag
obtained toward MWC 1080A (Cohen & Kuhi, 1979; Hillenbrand et al., 1992;
Oudmaijer et al., 1997), although the extinctions toward MWC 1080A and MWC
1080E can be somewhat different.

In Figure 4(b), the Br$\gamma$ map of Figure 2(a) is overlaid on the H$\alpha$
contours for comparison. The H$\alpha$ contours were obtained from Figure 1(b)
but smoothed using a Gaussian function with $\sigma$ = 5.0 pixel. The
Br$\gamma$ morphology is, in general, consistent with the H$\alpha$ image.
However, the Br$\gamma$ emission at a significance level of $>$3$\sigma$ was
observed only in the regions with the H$\alpha$ intensities higher than
$\sim$10-17 W m-2 arcsec-2 (the fifth lowest contour level). This intensity
value is actually the upper limit of the sole H$\alpha$ intensity, considering
the [N II] contribution to the IPHAS H$\alpha$ filter. The Br$\gamma$
counterpart for the arc-like H$\alpha$ feature was not detected. The lack of
the counterpart is likely due to the Br$\gamma$ detection limit of our IGRINS
observation. The Brackett line ratios shown in Figure 4(a) suggest that much
of the extended H$\alpha$ emission around MWC 1080A is likely stellar emission
from MWC 1080A scattered by dust, although the emissions in the saturated
region close to MWC 1080A might originate from an ionized stellar or disk
wind. On the other hand, we note that two compact Br$\gamma$ sources (Br 1080E
and Br YSO 1) are spatially coincident with two local H$\alpha$ peaks, as can
be seen in Figure 4(b). Therefore, the two H$\alpha$ peaks close to MWC 1080E
and YSO 1 also likely originate from the individual young stars as the compact
Br$\gamma$ sources do.

The IGRINS Br$\gamma$ map partially supplements the brightest region close to
MWC 1080A that was saturated in the IPHAS images and thus masked out. The
morphology of the Br$\gamma$-reflection nebulae is able to provide clues on
the spatial distribution of dusty material and outflow around MWC 1080A. We
note that Br SW shows two peaks separated by $\sim$1.$\arcsec$8 in slit
position S1 of Figure 2(b). The X positions of the close binary MWC 1080A and
MWC 1080B are overlaid by two red, vertical dashed lines in the PVD of S1. One
of the Br$\gamma$ peaks is coincident with the position of MWC 1080B (X
$\simeq$ +0.$\arcsec$5), but the other one is offset by about $-$1.$\arcsec$3
from MWC 1080A. We also note that another extended source Br NE 1 shows two
peaks in its PVD of slit position S4, although they are much fainter than
those of Br SW. The separation $(\sim$2$\arcsec$) between the two peaks in Br
NE 1 is similar to that for Br SW ($\sim$1.$\arcsec$8). The locations of the
four peaks with respect to MWC 1080A and the similarity between the peak
separations suggest a connection of the peaks in Br SW and Br NE 1 with the
bipolar, main outflow from MWC 1080A. The midpoint between the two peaks in Br
SW lies at X $\simeq$ $-$0.$\arcsec$4, and the midpoint for Br NE 1 lies at X
$\simeq$ +1$\arcsec$. Figure 2(a) shows the magenta dashed line connecting MWC
1080A and the two midpoints, which has a PA of $\sim$ 25$\arcdeg$. This is
somewhat different from the PA of 40$\arcdeg$ for the red solid line that
passes through MWC 1080A and the apex of the arc-like H$\alpha$ feature.
However, both the diagonal lines seem to, at least approximately, follow the
axis of the main outflow cavity inferred from the 13CO map. In other words,
the four peaks found in Br SW and Br NE 1 are likely to trace the main outflow
driven by MWC 1080A.

###  III.2. Molecular Hydrogen Lines

Figure 5.— Continuum-subtracted H2 1-0 S(1) map integrated over $-$60 km s-1
$\leq$ $V$ $\leq$ +60 km s-1, and PVDs for (b) the NW-SE slits S1–S6 and (c)
NE-SW slits S7–S10. The color scales are all in units of the detection
significance (signal/$\sigma$). In panel (a), the overlaid 13CO contours,
triangles, red dashed circles (young stars), red diagonal line (axis of the
main outflow cavity), and red bent line (arc-like H$\alpha$ feature) are the
same as in Figure 1(a). In panels (b) and (c), the origin of the NW-SE offset
X and NE-SW offset Y is the position of MWC 1080A; their positive directions
are indicated in (a). The contours on the PVDs represent a significance level
of 3$\sigma$. The twelve H2 1-0 S(1) sources identified in this study are also
denoted, together with the vertical solid lines that represent the spatial
extent, in the PVDs. The vertical dashed lines indicate the X or Y positions
of the young stars and the arc-like H$\alpha$ feature denoted in (a). Figure
6.— H2 1-0 S(1) line profiles of the diffuse sources, integrated over the
source region that is bounded by the vertical solid lines in Figures 5(b) and
(c). Each line profile was fitted with two Gaussians plus a linear continuum,
and the resulting linear continuum was subtracted from the line profile. The
best-fit Gaussian functions are overplotted with the blue (broad component;
$\Delta V$ $\geq$ 20 km s-1) and red (narrow component; $\Delta V$ $<$ 20 km
s-1) curves. The centroid velocity $V_{\mathrm{centroid}}$, FWHM velocity
width $\Delta V$, and line flux $F_{0}$ obtained from the fitting are shown in
each panel and also listed in Tables 2 and 3. There are no strong telluric OH
lines near the H2 1-0 S(1) line (Rousselot et al., 2000). The instrumental
profiles ($\Delta V$ $\simeq$ 6.5 km s-1 estimated from telluric OH lines)
have not been removed from the line profiles, which gives only a difference of
$<$1 km s-1 for $\Delta V$ $>$ 20 km s-1 and $\sim$2.8 km s-1 for $\Delta V$ =
9 km s-1.

We detected seven NIR H2 lines from the diffuse sources around MWC 1080 with
IGRINS. We first carried out a kinematic analysis for the brightest line, H2
1-0 S(1). Figure 5(a) shows a continuum-subtracted H2 1-0 S(1) map integrated
over $-$60 km s-1 $\leq$ $V$ $\leq$ +60 km s-1. The H2 1-0 S(1) PVDs for slit
positions S1–S10 are presented in Figures 5(b) and (c). In the PVDs, we found
a total of twelve H2 1-0 S(1) sources. The figures show their identification
names and spatial boundaries. H2 SW-E, H2 SW-W, H2 NW, H2 NE 1, and H2 NE 2
have narrow velocity widths centered at the systemic LSR velocity ($V$ = 0 km
s-1) and are located within the main outflow cavity near MWC 1080A. On the
other hand, H2 SE, H2 1080E, H2 knot A, H2 knot B, and H2 YSO 2 show much
broader velocity widths extending blueward and lie near/in the SE molecular
region. Along the NE axis of the main outflow cavity (slit position
S8+S9+S10), two faint sources were detected in a velocity range of $-$20 km
s-1 $\lesssim$ $V$ $\lesssim$ +20 km s-1, out of which the brightest one is
located near the NE edge of the cavity. They are referred to as H2 NE cavity
axis and H2 NE cavity edge.

To measure the H2 1-0 S(1) line profiles of the H2 sources, we integrated the
cube data over the source area that is bounded by the vertical solid lines in
Figures 5(b) and (c). The resulting H2 line profiles are shown in Figure 6. In
the figure, most of the H2 sources appear to have at least two velocity
components. We, therefore, fitted the individual line profiles with two
Gaussian functions plus a linear function and measured the centroid velocity
$V_{\mathrm{centroid}}$, FWHM velocity width $\Delta V$, and line flux $F_{0}$
for each velocity component. The best-fit profiles are shown in each panel of
Figure 6. Only the velocity components detected with a significance level of
$\geq$3$\sigma$ are presented in the figure. For the sake of convenience in
the identifications, we classified the detected velocity components into two
categories: narrow component with $\Delta V$ $<$ 20 km s-1 (red curves) and
broad one with $\Delta V$ $\geq$ 20 km s-1 (blue curves). The second row of
Table 2 shows the best-fit parameters for the narrow components and Table 3
for the broad components. The broad components for H2 SW-E, H2 SW-W, and H2 NW
were found to be relatively negligible, as shown in Figure 6, and thus are not
presented in Table 3.

The other six H2 lines, which are fainter than H2 1-0 S(1), are also shown in
Tables 2 and 3. We also extracted their line profiles and fitted them
individually using the same method as for H2 1-0 S(1). Some strong telluric OH
residuals found near the H2 lines were masked out before the line profiles
were measured. We found that the lines are also well represented by two
velocity components, as in the H2 1-0 S(1) line profile. We also classified
the velocity components like the H2 1-0 S(1) line components. The best-fit
results for the velocity components detected with a significance level of
$\geq$3$\sigma$ are presented in Tables 2 and 3. The narrow component for
these weak H2 lines was detected in most of the sources except for two
sources, H2 NE 2 and H2 NE cavity axis. On the other hand, the broad component
was not found in several sources, as shown in Table 3. In particular, the
broad component of H2 2-1 S(1) was detected only in H2 1080E.

####  III.2.1 Fluorescent and Thermal H2 Sources

Figure 7.— Level population diagrams of (a) the narrow and (b) broad
components for H2 sources. The normalized level populations (with 1$\sigma$
error bars) were calculated from the normalized line fluxes $F/F_{0}$ in
Tables 2 and 3. For eight sources without the H2 2-1 S(1) detections (red
points), the upper limits of the H2 2-1 S(1) fluxes were used. Rotation
temperatures $T_{\mathrm{rot},\,v=1}$ were derived from the best-fit slopes
(the blue lines) for $v$ = 1, $J$ = 1–4 levels, and vibration temperatures
$T_{\mathrm{vib},\,J=3}$ were from the best-fit slopes (the red lines) for $v$
= 1–2, $J$ = 3 levels, for which the results are given in each panel. In the
first panel, the open circles indicate the results obtained from the reddening
correction with $A_{V}$ = 5 mag, which caused only minor changes.

In the H2 1-0 S(1) PVDs of Section III.2, twelve H2 sources were identified
(see Figures 5(b) and (c)). We now classify them according to their excitation
mechanisms in two groups: fluorescent H2 sources and thermal ones. As shown in
Figure 6, many of them have both narrow and broad components. In particular,
two sources (H2 knot B and H2 YSO 2) show two clearly-separated components not
only in the spectra but also in the H2 1-0 S(1) PVDs. As listed in Table 2,
the narrow components of H2 1-0 S(1) have velocity widths of $\Delta V$ = 9–19
km s-1 and centroid velocities of $V_{\mathrm{centroid}}$ = $-$10 to +9 km
s-1, which are not significantly different from the systemic LSR velocity. On
the other hand, the broad components ($\Delta V>20$ km s-1) of H2 1-0 S(1)
appear to have substantially blueshifted line-centers (see Table 3). The broad
components for H2 SE, H2 1080E, H2 knot A, H2 knot B, and H2 YSO 2 have
$V_{\mathrm{centroid}}$ = $-$31 to $-$12 km s-1 and a much broader $\Delta V$
of 29 to 43 km s-1. The broad components for H2 NE cavity axis and H2 NE
cavity edge, detected along the NE cavity region, have
$(V_{\mathrm{centroid}},\,\Delta V)$ = $(-$12, 22) and ($-$4, 24) km s-1,
respectively. The difference in the line profiles suggests that the narrow and
broad components are excited by different mechanisms. The narrow components
with $\left|V_{\mathrm{centroid}}\right|\lesssim 10$ km s-1, indicating no
substantial motion relative to the systemic LSR motion, would be due to the
fluorescent H2 lines from the photodissociation regions (PDRs). On the other
hand, the broad components with blueshifted line centers
$(V_{\mathrm{centroid}}<0)$ are likely caused by thermal H2 emission from
shock-heated regions.

To estimate the relative contributions of the fluorescent and thermal
excitations in the H2 lines, we examined the H2 line ratios observed for the
individual sources. We detected only seven H2 lines belonging to the $v$ = 1–0
or 2–1 transition and thus utilized a simple method by Tanaka et al. (1989),
which is suitable to analyze a handful number of lines. No H2 lines from the
$v$ = 3–2 transition were detected. Using the H2 line fluxes normalized to the
H2 1-0 S(1) line flux given in Tables 2 and 3, we constructed the level
population diagrams of both narrow and broad components for each H2 source and
presented the results in Figure 7. To derive the normalized level population
ln($N$/g) $-$ ln($N_{0}$/g0), we used the transition probabilities from
Wolniewicz et al. (1998) and Equations (4)–(6) of Kaplan et al. (2017). For
eight sources without the H2 2-1 S(1) detection, we used the upper limits of
the H2 2-1 S(1) flux, which were calculated from the RMS noises in the
spectra. The wavelength differences between the H2 lines are so small (at most
$\sim$0.3 $\micron$) that there is no significant variation in extinction
between the lines. Therefore, no reddening correction was made; the reddening-
correction did not significantly alter the present result. We show a sample of
reddening-corrected results assuming $A_{V}$ = 5 mag in the first panel of
Figure 7(a). As shown in the figure, the reddening-corrected line ratios
denoted by open circles show only minor changes.

In the excitation diagram of Figure 7, the slope of the best-fit straight line
gives the excitation temperature (i.e., rotational or vibrational
temperature). Using uncertainty-weighted least-squares fitting, the rotation
temperature $T_{\mathrm{rot},\,v=1}$ was derived from the relative populations
between $J$ = 1–4 levels in the $v=1$ state (the blue lines), and the
vibration temperature $T_{\mathrm{vib},\,J=3}$ was from the relative
populations between the $(v,J)$ = (1, 3) and $(v,J)$ = (2, 3) states (the red
lines). The derived temperatures are denoted in each panel. For the narrow
components in Figure 7(a), the rotational temperature for all of the H2
sources except for two sources (H2 knot A and H2 NE cavity axis) was found to
be in a range of $T_{\mathrm{rot},\,v=1}$ = 550–835 K. The vibrational
temperature for the narrow components was derived as $T_{\mathrm{vib},\,J=3}$
= 3235–5083 K, except for the source H2 NE 2 without the H2 2-1 S(1)
detection. On the other hand, the narrow component for H2 knot A was found to
have a relatively higher $T_{\mathrm{rot},\,v=1}$ (1074 K) and a lower
$T_{\mathrm{vib},\,J=3}$ (2523 K) than the other narrow components. An
abnormally high $T_{\mathrm{rot},\,v=1}$ (5910 $\pm$ 2301 K), albeit with a
large uncertainty, was found for the narrow component of H2 NE cavity axis.
For the broad components in Figure 7(b), all H2 sources appear to have
$T_{\mathrm{rot},\,v=1}$ = 887–1505 K, which is, in general, higher than
$T_{\mathrm{rot},\,v=1}$ for the narrow components. We also note that the only
one source (H2 1080E) was found to have a non-zero flux in the broad component
of the H2 2-1 S(1) line. Hence, the vibrational temperature of the broad
component is available only from H2 1080E; the resulting vibrational
temperature of the broad component ($T_{\mathrm{vib},\,J=3}$ = 2241 K) was
found to be lower than those of the narrow components observed in other
sources (note that this source has no narrow component detected).

Figure 8.— (a) Rotation temperature $T_{\mathrm{rot},\,v=1}$ vs. vibration
temperature $T_{\mathrm{vib},\,J=3}$ for H2 sources, and (b) H2 1-0 S(1) map
overlaid on [S II] (continuum-subtracted) contours. In panel (a), red source
names are for the narrow components and blue ones for the broad components.
For sources without the H2 2-1 S(1) detection, the upper limits of the
vibration temperatures are applied. The square (fluorescent excitation) and
diamonds (thermal excitation) denote the values derived from the line ratios
presented in the theoretical models of Black & van Dishoeck (1987). The solid
line comes from Figure 1 of Tanaka et al. (1989) and indicates an empirical
relationship ($T_{\mathrm{rot},\,v=1}$ = 0.8 $\times$
$T_{\mathrm{vib},\,J=3}$) for purely the thermal excitation case. In panel
(b), the H2 1-0 S(1) map is the same as in Figure 5(a), and the twelve H2 1-0
S(1) sources identified in the PVDs (Figures 5(b) and (c)) are indicated by
their assigned names (“H2” was omitted). The [S II] contours come from Figure
8(d) of Poetzel et al. (1992). Red dashed circles (young stars), blue+red
lines (axes of the main outflow, “Outflow A,” and “Outflow B”), and a red bent
line (arc-like H$\alpha$ feature) are the same as in Figure 1.

Tanaka et al. (1989) discussed that the rotation and vibration temperatures
are similar around 2000 K in purely thermal excitation cases. As the
contribution of the fluorescent excitation increases, the rotation temperature
gets lower and the vibration temperature becomes higher. Their Figure 2 shows
several population diagrams for the thermal, fluorescent, and mixed excitation
cases, which can be compared with our population diagrams. In Figure 7(a),
most of the narrow components appear to belong to the mixed or nearly
fluorescent cases. Exceptionally, the narrow component of H2 knot A seems to
be much closer to the thermal case than the other narrow components, although
it is still in the mixed case. Similarly, the broad component for H2 1080E in
Figure 7(b) is also likely to be the mixed case dominated by the thermal
excitation. Because the other broad components have no H2 2-1 S(1) detected,
their $T_{\mathrm{vib},\,J=3}$ were calculated as the upper limits. The broad
components for H2 knot A, H2 knot B, and H2 YSO 2 have the upper limits of
$T_{\mathrm{vib},\,J=3}$ that are as low as for the case close to thermal
excitation.

In Figure 8(a), we compare $T_{\mathrm{rot},\,v=1}$ and
$T_{\mathrm{vib},\,J=3}$. We excluded the narrow component of H2 NE cavity
axis because it has a too high $T_{\mathrm{rot},\,v=1}$ with a large
uncertainty (5910 $\pm$ 2301 K). The points with red labels are for the narrow
components and those with blue ones are for the broad components. Black & van
Dishoeck (1987) presented various theoretical models for fluorescent and
thermal excitations of the H2 lines. Using the H2 line intensities in their
Table 2, we calculated $T_{\mathrm{rot},\,v=1}$ and $T_{\mathrm{vib},\,J=3}$
predicted from their models. We used only the H2 lines that were detected in
our observation. In Figure 8(a), the open squares located near the upper left
corner indicate the results from Models 1–32 of Black & van Dishoeck (1987),
which are for the fluorescent excitation cases. On the other hand, the open
diamond near the lower right corner denotes the result from their Model S2 for
the thermal excitation case. In addition, adopting from Figure 1 of Tanaka et
al. (1989), an empirical relationship between the rotation and vibration
temperatures for purely the thermal excitation case is overlaid by a solid
line. Figure 8(a) confirms the results of the previous paragraph more clearly.
Most of the narrow components, except that of H2 knot A, are closer to the
fluorescent excitation than to the thermal excitation. On the other hand, the
broad components of H2 1080E, H2 knot A, H2 knot B, and H2 YSO 2 appear to be
closer to the thermal excitation. The broad components of H2 SE, H2 NE cavity
axis, and H2 NE cavity edge have too high upper-limits of
$T_{\mathrm{vib},\,J=3}$ to determine a dominant excitation mechanism.
However, their $T_{\mathrm{rot},\,v=1}$ (887, 1169, and 1189 K) are higher
than $T_{\mathrm{rot},\,v=1}$ (550–835 K) for the narrow components close to
the fluorescent excitation, which suggests a possibility for the dominance of
the thermal excitations. We also note that the narrow component of H2 knot A,
unlike the other narrow components, lies close to the thermal excitation
despite its narrow velocity width.

Figure 9.— H2 1-0 S(1) velocity channel maps ($-$12 km s-1 $\leq$ $V$ $\leq$
+12 km s-1) around MWC 1080A. The color scales are all in units of the
detection significance (signal/$\sigma$). The integrated velocity range is
indicated at the top of each channel map. The eight H2 sources with
fluorescent H2 lines are indicated by their assigned names. The overlaid 13CO
contours, triangles (young stars), and red diagonal line (axis of the main
outflow cavity) are the same as in Figure 1(a).

In Figure 8(b), the H2 1-0 S(1) map of Figure 5(a) is overlaid on the
continuum-subtracted [S II] contours for comparison. The [S II] contours
together with six slit positions for the [S II] spectroscopy (solid lines)
were adopted from Figure 8(d) of Poetzel et al. (1992). Six [S II] HH objects
(“Knot A” to “Knot F”) identified by Poetzel et al. (1992) are also shown in
the figure. The correlation between the H2 1-0 S(1) and [S II] morphologies
seems to be rather weak. However, we found that the brightest H2 1-0 S(1)
emission (H2 knot A) was detected near the [S II] peak of “Knot A.” This knot
is the brightest one among the six [S II] HH objects. As already discussed,
the H2 line ratios in Figure 8(a) indicate that both the narrow and broad
components of H2 knot A are likely thermal H2 emission from shock-heated gas.
This suggests that “Knot A” is probably an outflow feature forming shocked
regions. We also note that the broad components detected along the NE axis of
the main outflow cavity (H2 NE cavity axis and H2 NE cavity edge) might be
related to “Knot D” and “Knot E” although the IGRINS slit positions are
slightly displaced from the [S II] HH objects. In particular, H2 NE cavity
edge is almost coincident with the arc-like H$\alpha$ feature (indicated by a
red bent line in the figure); this is also shown in Figure 5(c). Figure 8(a)
shows that the broad components of H2 NE cavity axis and H2 NE cavity edge
might be a thermal H2 emission. If this is the case, at least some portions of
“Knot D”, “Knot E”, and the arc-like H$\alpha$ feature could be associated
with shock-heated regions.

The IGRINS kinematic results for the narrow components of H2 can provide
information on the geometry of the main outflow cavity near MWC 1080A. The H2
line ratios imply that the narrow components for the eight H2 sources around
MWC 1080A (H2 SW-E, H2 SW-W, H2 NW, H2 SE, H2 NE 1, H2 knot B, H2 YSO 2, and
H2 NE 2) are the H2 lines induced predominantly by the fluorescent excitation,
as shown in Figure 8(a). Therefore, we suggest that the narrow components of
the H2 lines originate from the PDRs formed on the internal surfaces of the
main outflow cavity. In Figure 9, we plot the H2 1-0 S(1) velocity channel
maps at an interval of 5 km s-1 over the velocity range of $-12\leq V\leq 12$
km s-1 where the narrow components are dominant. The first channel map was
obtained over the whole velocity range of $-$12 to +12 km s-1. In this map, H2
1-0 S(1) appears much brighter along the NW and SE boundaries of the cavity
than near the central cavity axis. This property is shown more clearly in the
channel map for $-$2 km s-1 $\leq$ $V$ $\leq$ +2 km s-1 near the systemic LSR
velocity. These bright regions are likely to be limb-brightened PDRs on the
main outflow cavity walls. Large column densities along the lines of sight to
the boundaries make the boundaries brighter than the other sightlines that are
close to the cavity axis. We also note that the brightest peak (H2 NW) is
almost coincident with the apex of the NW 13CO boundary, which is the cavity
boundary closest to MWC 1080A. The sources H2 SW-E, H2 SE, H2 NE 1, and H2 NE
2 that are close to the central cavity axis become slightly brighter in the
two, negative (blueshift) velocity channel maps for $-$12 km s-1 $\leq$ $V$
$\leq$ $-$3 km s-1. In particular, the brightest locations of H2 SW-E, H2 SE,
and H2 NE 1 appear to move closer to the cavity axis in the higher-blueshift
velocity maps. These variations appear more clearly in the H2 1-0 S(1) PVDs
(Figure 5(b)), where H2 SW-E and H2 NE 1 show notable radial velocity
gradients along the X direction (higher blueshift towards X = 0$\arcsec$).
From these results, we conclude that the narrow components of H2 SW-E, H2 SE,
H2 NE 1, and H2 NE 2 trace the PDRs on the front surface of the main outflow
cavity wall, which is expanding outward with a velocity of $\sim$10–15 km s-1.
In the positive (redshift) velocity channel maps for +3 km s-1 $\leq$ $V$
$\leq$ +12 km s-1, H2 knot B appears slightly brighter than in the velocity
channel map for $-$2 km s-1 $\leq$ $V$ $\leq$ +2 km s-1. As can be seen in
Figure 5(b), the narrow component of H2 knot B also shows a radial velocity
gradient along the X direction in the H2 1-0 S(1) PVD (higher redshift towards
X = 0$\arcsec$). This tendency suggests that the region traced by H2 knot B
may be a PDR formed on the part of the rear surface of the cavity wall. It is
also noticeable that H2 knot B, tracing the rear part of the cavity wall, is
much fainter than those tracing the front part.

###  III.3. [Fe II] $\lambda$1.644 $\micron$ Line

Figure 10.— Continuum-subtracted [Fe II] map integrated over $-$300 km s-1
$\leq$ $V$ $\leq$ +50 km s-1, and PVDs for (b) the NW-SE slits S1–S6 and (c)
NE-SW slits S7–S10. The color scales are all in units of the detection
significance (signal/$\sigma$). In panel (a), the overlaid 13CO contours,
triangles, red dashed circles (young stars), red diagonal line (axis of the
main outflow cavity), and red bent line (arc-like H$\alpha$ feature) are the
same as in Figure 1(a). In panels (b) and (c), the origin of the NW-SE offset
X and NE-SW offset Y is the position of MWC 1080A; their positive directions
are indicated in (a). The contours on the PVDs represent a significance level
of 3$\sigma$. The five [Fe II] sources identified in this study are also
denoted, together with the vertical solid lines that represent the spatial
extent, in the PVDs. The vertical dashed lines indicate the X or Y positions
of the young stars and the arc-like H$\alpha$ feature denoted in (a). Figure
11.— [Fe II] line profiles for the diffuse sources, integrated over the source
region that is bounded by the vertical solid lines in Figures 10(b) and (c).
Each line profile was fitted with a Gaussian function plus a linear continuum
(For Fe knot A, we used two Gaussian functions), and the resulting linear
continuum was subtracted from the line profile. The best-fit Gaussian
functions are overplotted with the blue or red curves as well. The centroid
velocity $V_{\mathrm{centroid}}$, FWHM velocity width $\Delta V$, and line
flux $F_{0}$ obtained from the fitting are shown in each panel and also listed
in Table 4. The green dotted lines indicate the positions of the telluric OH
lines (Rousselot et al., 2000). There are several telluric residuals in the
positive $V$ domain, but the blueshifted part of the [Fe II] lines was not
severely affected by them. The two shaded areas denote the $V$ domains
containing strong telluric residuals, which were masked out when the line
profiles were measured. The instrumental profiles ($\Delta V$ $\simeq$ 6.5 km
s-1 estimated from telluric OH lines) have not been removed from the line
profiles, which gives only a difference of $<$1 km s-1 for $\Delta V$ $>$ 20
km s-1.

We also detected the [Fe II] $\lambda$1.644 $\micron$ forbidden line from the
diffuse sources around MWC 1080 with IGRINS. This is the only Fe line detected
in our observations. Figure 10(a) shows a continuum-subtracted [Fe II] map
integrated over $-$300 km s-1 $\leq$ $V$ $\leq$ +50 km s-1. The [Fe II] PVDs
for slit positions S1–S10 are also presented in Figures 10(b) and (c). In the
PVDs, we identified a total of five [Fe II] sources. Their identification
names and spatial boundaries are also shown in the figure. The features seen
in S7 are a part of Fe knot B observed in S5+S6. The sharp peak found at X
$\simeq$ 3.$\arcsec$8 in S2 is likely due to a cosmic ray event that was not
removed by the basic data reduction. In S5+S6, the [Fe II] line profile of Fe
knot A appears to consist of two separate velocity components. One is the
high-blueshift component that is found in a velocity range of $-$300 to $-$200
km s-1, and the other is the low-blueshift component in a velocity range of
$-$100 to 0 km s-1. The low-blueshift velocity component extends more toward
YSO 1 than the high-blueshift one. In the same silt position, Fe knot B was
also detected in a velocity range of $-200\leq V\leq 0$ km s-1, at a location
close to YSO 1. In S4, Fe 1080E was detected with $V$ $\simeq$ $-$100 to 0 km
s-1, although it is somewhat faint. Fe SE found in S3 has a high-blueshift
component in $-300\leq V\leq-200$ km s-1, which is similar to the high-
blueshift component of Fe knot A. In S8+S9+S10, weak, sparse [Fe II] features
were detected near the NE edge of the main outflow cavity; those are
altogether referred to as Fe NE cavity edge. This [Fe II] source shows a low-
blueshift component in $-50\leq V\leq 0$ km s-1.

Figure 11 shows the [Fe II] line profiles for each source region. To measure
the centroid velocity $V_{\mathrm{centroid}}$, FWHM velocity width $\Delta V$,
and line flux $F_{0}$ for the five [Fe II] sources, we fitted them with the
same method as for Br$\gamma$ and H2 1-0 S(1); the best-fit profiles are shown
in Figure 11. Two velocity intervals, containing strong telluric OH residuals,
were masked out before the line profiles were measured. Only the velocity
components detected with a detection significance $F_{0}/\sigma_{F_{0}}$ $>$3
are presented in the figure and also listed in Table 4. All of the [Fe II]
sources appear to have a negative (blueshift) $V_{\mathrm{centroid}}$
($<$$-$10 km s-1) and broad $\Delta V$ ($>$43 km s-1). In particular, Fe knot
A was fitted to have two velocity components of $V_{\mathrm{centroid}}$ =
$-$233 and $-$48 km s-1.

####  III.3.1 Shock-induced [Fe II] Sources

Figure 12.— (a) [Fe II] map overlaid on [S II] (continuum-subtracted)
contours, and [Fe II] (color image) and H2 1-0 S(1) (contours) PVDs for (b)
the NW-SE slits S3–S6 and (c) NE-SW slits S7–S10. In panel (a), the [Fe II]
map is the same as in Figure 10(a), and the five [Fe II] sources identified in
the PVDs (Figures 10(b) and (c)) are indicated by their assigned names. The [S
II] contours come from Figure 8(d) of Poetzel et al. (1992). Red dashed
circles (young stars), blue+red lines (axes of the main outflow, “Outflow A,”
and “Outflow B”), and a red bent line (arc-like H$\alpha$ feature) are the
same as in Figure 1. In panels (b) and (c), the H2 1-0 S(1) contours come from
Figures 5(b) and (c), and range from 3$\sigma$ to 43$\sigma$ in a 5$\sigma$
equal interval (except S8+S9+S10, showing 3$\sigma$, 5$\sigma$, and 7$\sigma$
levels). The [Fe II] PVDs are from Figures 10(b) and (c) but were smoothed
using a Gaussian function with $\sigma$ = 1.0 pixel. The H2 and [Fe II]
sources are indicated by their names. The vertical dashed lines indicate the X
or Y positions of the young stars and the arc-like H$\alpha$ feature denoted
in (a).

In the [Fe II] PVDs of Section III.3, five [Fe II] sources were identified
(see Figure 10). As shown in Figure 11 and Table 4, all [Fe II] lines, except
one source (Fe NE cavity edge), are found to be blueshifted by
$V_{\mathrm{centroid}}<-42$ km s-1 and have a broad velocity width $\Delta
V>77$ km s-1; Fe NE cavity edge has the lowest blueshift
($V_{\mathrm{centroid}}=-10$ km s-1) and the narrowest width ($\Delta V=43$ km
s-1). These line profiles indicate that all the [Fe II] sources likely
originate from the shock-heated regions.

In Figure 12(a), the [Fe II] map of Figure 10(a) is overlaid on the [S II]
(continuum-subtracted) contours for comparison. The [S II] contours are the
same as in Figure 8(b). The brightest [Fe II] emission (Fe knot A) was
detected near the [S II] peak of “Knot A,” just like the source H2 knot A was.
The detection of the shock-induced [Fe II] and H2 emission at the location of
“Knot A” strongly supports that “Knot A” is an outflow forming shock-heated
region. The [Fe II] $\lambda$1.644 $\micron$ emission was also detected
throughout the region between the [S II] peak and YSO 1, which overlaps with
“Knot A.” The source Fe NE cavity edge, together with H2 NE cavity edge, was
detected near the arc-like H$\alpha$ feature (indicated by a red bent line in
the figure). Although Fe NE cavity edge has a somewhat small blueshift
$V_{\mathrm{centroid}}=-$10 km s-1 and a relatively narrow velocity width
$\Delta V=43$ km s-1, it also could be shock-induced; this will be discussed
in Section IV.1.1.

To compare the spatial and kinematic distributions between the [Fe II] and H2
sources in detail, we overplotted the H2 1-0 S(1) PVDs (contours) on the [Fe
II] PVDs (color image) for slit positions S3–S10 in Figures 12(b) and (c). In
the figures, the associations between the [Fe II] and H2 sources are found at
several positions. In $-$10.$\arcsec$0 $\lesssim$ X $\lesssim$ $-$7.$\arcsec$5
of slit position S5+S6, the low-blueshift component of Fe knot A
($V_{\mathrm{centroid}}$ = $-$48 km s-1) seems to be associated with both the
narrow and broad components of H2 knot A. In the velocity space, the peak
position of H2 knot A appears to align along with the lowest blueshift
boundary ($V$ $\simeq$ $-$25 to $-$10 km s-1) of the low-blueshift component
of Fe knot A, which strongly supports the physical association between them.
On the other hand, the high-blueshift component of Fe knot A
($V_{\mathrm{centroid}}$ = $-$233 km s-1) has no counterpart in the H2
emission. In $-$6.$\arcsec$0 $\lesssim$ X $\lesssim$ $-$4.$\arcsec$5, the
lowest blueshift boundary ($V$ $\simeq$ $-$30 km s-1) of Fe knot B shows an
association with the broad component of H2 knot B, although the H2 source
extends much more towards the NW direction (up to X $\simeq$ $-$2.$\arcsec$0)
than Fe knot B. In slit position S4, Fe 1080E appears to overlap with H2 1080E
although the correlation between them is not clear. In slit position S3, Fe SE
and H2 SE are observed at similar locations, but they show neither clear
spatial nor kinematic relationships. In slit position S8+S9+S10, Fe NE cavity
edge and H2 NE cavity edge are spatially coincident and are located just
inside the arc-like H$\alpha$ feature, as indicated by a vertical dashed line
in the figure; this suggests that Fe NE cavity edge and H2 NE cavity edge
could be associated with the arc-like H$\alpha$ feature. In addition, in the
velocity space, the H2 peak seems to lie near the lowest blueshift boundary
($V$ $\simeq$ $-$5 km s-1) of Fe NE cavity edge; the property is the same as
that found for Fe knot A/H2 knot A and Fe knot B/H2 knot B in S5+S6. We also
note that the [Fe II] and H2 features seen in 5.$\arcsec$0 $\lesssim$ Y
$\lesssim$ 6.$\arcsec$5 of slit position S7 are identical to Fe knot B and H2
knot B, respectively, in slit position S5+S6. In 0.$\arcsec$0 $\lesssim$ Y
$\lesssim$ 5.$\arcsec$0 of slit position S7, the broad component of H2 YSO 2
was detected with no corresponding [Fe II] source. A portion of it seems to be
connected to the SW part of H2 knot B. However, its peak location (at $V$
$\simeq$ $-$20 km s-1) is much closer to YSO 2, suggesting its association
with YSO 2, rather than with H2 knot B.

##  IV. Discussion

###  IV.1. Stellar Outflows

####  IV.1.1 Main Outflow from MWC 1080A

It has been observed in the outflows of young stars that the H2 emission is
found in relatively low-velocity ranges while the [Fe II] emission is found in
higher velocity ranges (e.g., Pyo et al., 2002; Davis et al., 2003; Takami et
al., 2006; Oh et al., 2016b). It has been interpreted that the [Fe II] and H2
emissions, respectively, originate from high-velocity collimated outflows and
low-velocity entrained ambient molecular gas. This suggests that H2/Fe NE
cavity edge shown in Figure 12(c) is caused by shock-excitation due to a
stellar outflow, although the H2 and [Fe II] emissions were detected very
weakly. More specifically, we suggest that the NE main outflow from MWC 1080A
would be the excitation source of H2/Fe NE cavity edge, based on the spatial
coincidence between H2/Fe NE cavity edge, the arc-like H$\alpha$ feature, and
the NE 13CO boundary (see Figures 1 and 12(c)).

The centroid velocity $V_{\mathrm{centroid}}$ of the [Fe II] line in H2/Fe NE
cavity edge was observed to be relatively low ($-$10 km s-1 in Figure 11)
compared to those observed from the outflows of other young stars. This
difference can be explained if the inclination angle of the NE main outflow
from MWC 1080A is close to 0$\arcdeg$ with respect to the sky plane. Wang et
al. (2008) showed that the overall velocity distributions of 13CO and CS are
mostly blueshifted by $-$5 to 0 km s-1, and most of them are located around
the NE cavity region, as can be seen in Figure 1(a). Therefore, their velocity
distributions agree well with our kinematic estimation for the NE main outflow
of MWC 1080A. Additionally, Alonso-Albi et al. (2009) obtained an inclination
angle of $\sim$80$\arcdeg$ for the circumstellar disk and large toroidal
envelope around MWC 1080A by SED fitting. The nearly edge-on orientation of
the circumstellar disk is compatible with our low inclination angle inferred
for the main outflow of MWC 1080A. Davis et al. (2003) reported a YSO, HH 379
IRS, with the $V_{\mathrm{centroid}}$ near the systemic LSR velocity for both
H2 and [Fe II], and presented the same explanation as for MWC 1080A. They also
argued that [Fe II] still traces the high-velocity collimated outflow based on
the result that $\Delta V$ for [Fe II] is about twice as broad as $\Delta V$
for H2. Our velocity widths derived from H2/Fe NE cavity edge ($\Delta V$ = 24
km s-1 for H2 1-0 S(1) and $\Delta V$ = 43 km s-1 for [Fe II]) show the same
trend as that for HH 379 IRS.

The broad component of H2 NE cavity axis may also be caused by the NE main
outflow, although no [Fe II] counterpart was detected and the H2 line ratios
could not obviously confirm the thermal origin of the lines. The kinematic
results of the broad component ($V_{\mathrm{centroid}}$ = $-$12 km s-1 and
$\Delta V$ = 22 km s-1 for H2 1-0 S(1)) support the possibility that it might
be related to shock-heated regions by the NE main outflow. As we suggested in
Section III.2.1, the broad component can be associated with two [S II] HH
objects, “Knot D” and “Knot E”, located near the NE axis of the main outflow
cavity.

In fact, the narrow component of H2 was also detected along the NE axis of the
main outflow cavity. In Figure 6, H2 NE cavity axis has both the narrow and
broad components. Although the H2 line ratios obtained in this study could not
reveal the dominant excitation mechanism for the narrow component, its
kinematic results of the redshifted $V_{\mathrm{centroid}}$ (+9 km s-1) and
narrow $\Delta V$ (14 km s-1) imply that the narrow component unlikely belongs
to the thermal H2 lines related to the NE main outflow. Rather, it may come
from PDRs formed on the rear surfaces of the NE cavity wall. The exciting
photons emitted from MWC 1080A can reach the distant surfaces effectively
through the low-density medium inside the NE cavity.

In Section II.2, we reported a few faint H$\alpha$ features located far away
in the SW direction from MWC 1080A. We suggest that the H$\alpha$ features
around (RA, DEC) $\sim$ (23h17m21.6s, +60$\arcdeg$50$\arcmin$08$\arcsec$) in
Figure 1(b) (denoted by a dashed circle) could be related to the SW counter
outflow corresponding to the NE main outflow. As indicated by a blue+red line
with PA = 40$\arcdeg$ in the figure, the SW faint H$\alpha$ features lie near
the SW extension of the diagonal line passing through MWC 1080A and the apex
of the NE arc-like H$\alpha$ feature. They are away from MWC 1080A by about
twice the distance between MWC 1080A and the NE arc-like H$\alpha$ feature. As
shown in Figure 1(a), the 13CO boundary is opened toward the SW direction from
MWC 1080A, which means that the mediums toward the SW direction have a
relatively low density. This can make the SW main outflow move much farther
from MWC 1080A and be seen much more faintly. Because the NE main outflow was
found to be a blueshifted outflow, the SW main outflow is expected to be a
redshifted outflow, although it also likely has a low inclination angle with
respect to the sky plane. The blueshifted and redshifted parts of the main
outflow are denoted by the blue and red colors on the line with PA =
40$\arcdeg$ in Figure 1(b).

####  IV.1.2 New Outflows A and B

Hartigan et al. (1987) presented bow shock models of HH outflows for a wide
range of shock velocities (20–400 km s-1) and various inclination angles. One
of their results is that double-peaked line profiles (high velocity close to
shock velocity and low velocity close to 0 km s-1) observed from the HH
outflows are predicted from bow shocks with high ($>$150 km s-1) shock
velocities and large ($>$45$\arcdeg$) inclination angles with respect to the
sky plane. This can explain the high- and low-blueshift components of Fe knot
A shown in Figure 12(b). Adopting the model, the high-blueshift [Fe II]
component ($V_{\mathrm{centroid}}$ = $-$233 km s-1) would originate mostly
from the apex of a bow shock, whereas the low-blueshift [Fe II] component
($V_{\mathrm{centroid}}$ = $-$48 km s-1) from a portion of the bow wings. We
note that the seeing (FWHM $\sim$0.$\arcsec$6) during the observations was
comparable to the IGRINS slit width (0.$\arcsec$63), meaning that they are
both narrower than the whole size of the bow shock. Therefore, a substantial
portion of the emission from the bow wings could be missed, leading to a
weakening of the low-blueshift [Fe II] component compared to the high-
blueshift one. In fact, the high-blueshift [Fe II] component has two velocity
peaks of $V$ $\simeq$ $-$250 and $-$200 km s-1, as can be seen in Figure
12(b). This can be due to a slight displacement of slit position S5 from the
exact location of the bow apex. The bow shock model of Hartigan et al. (1987)
also shows that the shock velocity is similar to the full width at zero
intensity (FWZI) of the line profiles observed from an HH outflow independent
of its inclination angles. From the PVD in Figure 12(b) and the line profile
fitting in Figure 11, the FWZI of Fe knot A is estimated to be about 300–400
km s-1. Therefore, a shock velocity of 300–400 km s-1 and an inclination angle
of $>$45$\arcdeg$ are expected for the outflow related to Fe knot A. We refer
to this outflow as “Outflow A.”

In Figure 12(b), H2/Fe knot A shows a velocity structure in which the H2 peak
is coincident with the lowest blueshift boundary of the low-blueshift [Fe II]
component. This is the velocity structure that is expected from the ambient H2
gas entrained by the [Fe II] outflow shock (e.g., Davis et al., 2001; Pyo et
al., 2002; Davis et al., 2003; Oh et al., 2016b). Therefore, H2 knot A (both
the narrow and broad components), associated with the low-blueshift component
of Fe knot A, is likely molecular gas entrained by the shocks propagating in
the bow wing regions of “Outflow A.” The estimated shock velocity of “Outflow
A” (about 300–400 km s-1) highly exceeds the H2 dissociation speed (generally
35–50 km s-1), which would prevent the H2 emission associated with the high-
blueshift component of Fe knot A. On the other hand, in the bow wing regions,
the normal component of the shock velocity with respect to the bow shock front
can be below the H2 dissociation speed.

We associate “Outflow A” with the brightest [S II] HH object, “Knot A.” As can
be seen in Figures 8(b) and 12(a), slit position S5 is aligned well with the
SE extension of “Knot A,” and the brightest locations of the detected [Fe II]
and H2 emissions are almost coincident with the [S II] peak of “Knot A,”
considering the seeing size of the [S II] map (at most 2.$\arcsec$0, Poetzel
et al., 1992). Poetzel et al. (1992) also presented the [S II] spectroscopic
result for a long slit passing through “Knot A” (the 10$\arcsec$ line in
Figures 8(b) and 12(a)). They detected two separate velocity components
($-$215 and $-$85 km s-1) at the [S II] peak of “Knot A” (see their Figure
12(a)). Considering their observed radial velocities with respect to the
systemic velocity of the MWC 1080 system (about $-$39 km s-1 heliocentric,
Poetzel et al., 1992), the [S II] components (converted to $-$176 and $-$46 km
s-1) agree well with the high-blueshift ($V_{\mathrm{centroid}}$ = $-$233 km
s-1) and low-blueshift ($V_{\mathrm{centroid}}$ = $-$48 km s-1) [Fe II]
components of Fe knot A, respectively. The difference in velocities between
the high-blueshift components can be due to a slight mismatch between their
slit position and our slit position S5. Based on the above spatial and
kinematic coincidence, we conclude that “Knot A” represents “Outflow A,” a
highly-blueshifted outflow (with a shock velocity of 300–400 km s-1 and an
inclination angle of $>$45$\arcdeg$), and H2/Fe knot A is a shock-induced line
emission by this outflow. However, it is difficult to identify the driving
young star for “Outflow A” in this study. Nevertheless, based on the
morphology of “Knot A” extending towards the SE direction in the [S II] map,
we propose that MWC 1080E and YSO 1 are the most probable candidates. As
presented in Section III.1.1, the detection of the Br$\gamma$ emission from
them in the present work supports the existence of their active accretion and
winds. In Figures 1(b), 8(b), and 12(a), we denoted the blueshifted and
redshifted parts of “Outflow A” in the blue and red lines with PA =
135$\arcdeg$, assuming that YSO 1 is the driving source of “Outflow A.” In
this study, we could not find any evidence for the redshifted part of “Outflow
A,” but its plausible position was indicated by a red dashed line.

As for H2/Fe knot A, a strong kinematic correlation between the H2 and [Fe II]
emissions from H2/Fe knot B shown in Figure 12(b) suggests that they are also
likely related to an outflow shock and ambient H2 gas entrained by the shock.
However, the driving source of H2/Fe knot B cannot be YSO 1 because their
blueshifted components extend toward both the SE and NW directions from YSO 1,
as can be seen in Figure 12(b). One possibility is that they might be related
to another [S II] HH object, “Knot B.” The faint H$\alpha$ features around
(RA, DEC) $\sim$ (23h17m18.5s, +60$\arcdeg$50$\arcmin$30$\arcsec$) in Figure
1(b), as denoted by a dashed circle, are possibly related to the counter
outflow corresponding to “Knot B.” This is based on the identical bipolar
outflowing direction between them, as indicated by a blue+red line with PA =
77$\arcdeg$ in the figure. We suggest that “Knot B” and the faint H$\alpha$
features could be related to another bipolar outflow from a young star around
MWC 1080A. We refer to this bipolar outflow as “Outflow B.” Like the main
outflow from MWC 1080A, “Outflow B” also has a similar morphological
characteristic: bright and close in the NE direction, and faint and distant in
the SW direction.

As can be seen in Figures 8(b) and 12(a), H2/Fe knot B is located near the
line of PA = 77$\arcdeg$ representing the axis of “Outflow B.” Poetzel et al.
(1992) detected a $-$141 km s-1 (with respect to the systemic velocity) [S II]
component at $\sim$3$\arcsec$ north from the [S II] peak of “Knot A” in their
slit position of 10$\arcsec$ (see their Figure 12(a)). Its position lies
almost on the line of PA = 77$\arcdeg$ (the intersection of the 10$\arcsec$
line and the red dashed line for “Outflow B” in Figure 12(a)). The [S II]
component has a similar velocity to $V$ $\simeq$ $-$150 km s-1 for the [Fe II]
component seen at $-$7.$\arcsec$0 $\lesssim$ X $\lesssim$ $-$6.$\arcsec$0 in
slit position S5+S6 of Figure 12(b). Moreover, Poetzel et al. (1992) detected
a $-$156 km s-1 [S II] component for “Knot B” itself in their slit position of
20$\arcsec$ (see their Figure 12(b)). The fact that “Knot B,” Fe knot B, and
an intermediate component between them all have similar blueshifts supports
their associations. Therefore, we propose that H2/Fe knot B might be related
to “Knot B” corresponding to the blueshifted part of “Outflow B.” Considering
active young stars located near the axis of “Outflow B,” MWC 1080E and MWC
1080B can be possible candidates for the driving young star for “Outflow B.”
In Figures 1(b), 8(b), and 12(a), the blueshifted and redshifted parts of
“Outflow B” are denoted in the blue and red lines with PA = 77$\arcdeg$
assuming that MWC 1080E is the driving source of “Outflow B.”

Fe SE and Fe 1080E were also detected near the axis of “Outflow B,” as can be
seen in Figure 12(a). Poetzel et al. (1992) detected a $-$241 km s-1 (with
respect to the systemic velocity) [S II] component in their slit positions
passing through Fe SE (see their Figure 11). Its velocity is almost the same
as $V_{\mathrm{centroid}}$ for Fe SE ($-$239 km s-1). If Fe SE and/or Fe 1080E
are also truly related to the blueshifted part of “Outflow B,” MWC 1080E
cannot be the driving source for “Outflow B” because they are located in the
opposite direction from MWC 1080E with respect to “Knot B.” Fe SE, Fe 1080E,
and “Knot B” all have negative (blueshift) velocities. In fact, there are many
driving source candidates around MWC 1080A, and their outflowing axes can
overlap with each other on the projected sky plane. Therefore, it is difficult
to find the actual origins of Fe SE and Fe 1080E in this study. The similar
velocity ranges ($V$ $\simeq$ $-$300 to $-$200 km s-1) between the high-
blueshift component of Fe knot A and the source Fe SE, imply another
possibility of their associations as well. Further observations are needed to
reveal their origins definitely.

In the Appendix, we present the H2 1-0 S(1) and [Fe II] velocity channel maps
using the data obtained from twelve, additional slit observations. Despite bad
weather conditions during these observations, we were able to obtain a few
meaningful results. In Figure 14(a), the bright H2 1-0 S(1) regions appear
roughly along the CS molecular boundary. As the radial velocity varies from
$-$50 km s-1 to $-$1 km s-1, the bright H2 regions move into the deeper inside
of the CS molecular region, which agrees with the H2 emission observed within
slit position S5. This shows a possibility that “Outflow A” can be related to
the CS molecular boundary distorted toward the extending direction of “Knot A”
(see the yellow line with PA = 135$\arcdeg$ in the figure). However, we note
that the 13CO molecular boundary near “Knot A” shows no distorted shape, as
can be seen in Figure 5(a). It might be because the CS map traces molecular
gas with a higher density than the 13CO map (Wang et al., 2008). In Figure
14(b), an [Fe II] region was detected additionally at $-$180 km s-1 $<$ $V$
$<$ $-$121 km s-1, which is located near the axis of “Outflow B” (see the blue
line with PA = 77$\arcdeg$ in the figure). This [Fe II] emission may be the
counterpart for the $-$141 km s-1 [S II] component detected by Poetzel et al.
(1992) at the same location, and it supports the possible association between
H2/Fe knot B and “Knot B.”

###  IV.2. Origins of Atomic Hydrogen Line Emission

####  IV.2.1 Extended Emission

Figure 13.— IPHAS H$\alpha$ images overlaid on (a) 13CO and (b) [S II]
contours. The H$\alpha$ image comes from Figure 1(b), but its color scale has
been changed slightly. The 13CO contours were adapted from Figure 2 of Wang et
al. (2008) and are the same as in Figure 1(a). The [S II] contours were
adapted from Figure 8(d) of Poetzel et al. (1992) and are the same as in
Figures 8(b) and 12(a). Triangles, red dashed circles (young stars), blue+red
lines (axes of the main outflow, “Outflow A,” and “Outflow B”), and a red bent
line (arc-like H$\alpha$ feature) are the same as in Figure 1. Panel (c) shows
an H$\alpha$-to-continuum ratio map for the whole MWC 1080 region, where the
three outflows and the arc-like H$\alpha$ feature are indicated. The ratio map
was made from the IPHAS H$\alpha$\- and $r$-filter images. A close-up view of
the central region of panel (c) is overlaid on the [S II] contours in panel
(d).

From the analysis of the kinematics and line ratio for the hydrogen Brackett
emission lines, a large portion of the extended H$\alpha$ emission around MWC
1080A shown in Figure 1(b) was confirmed to trace dusty nebulae that scatter
the stellar H$\alpha$ emission from MWC 1080A. In Figure 13(a), the H$\alpha$
image of Figure 1(b) is overlaid on the 13CO contours of Figure 1(a). In
general, the H$\alpha$ emission around MWC 1080A correlates well with the main
outflow cavity apparent in the 13CO map. The H$\alpha$ emission is bright
along the NW and SE boundaries of the cavity near MWC 1080A. This is very
similar to the 11.2 $\micron$ morphology shown in Figure 5 of Li et al.
(2014). Based on the mid-IR (11.2, 11.6, and 18.5 $\micron$) morphology
correlated well with the cavity structure, they discussed that the extended
mid-IR emission is emitted by warm dust located close to the main outflow
cavity walls. Similarly, the H$\alpha$ emission brightening along the cavity
boundaries is likely due to the emission scattered by dust on the surfaces of
the cavity.

The bright Br$\gamma$ emission detected in the region close to MWC 1080A,
masked out because of saturation in the IPHAS H$\alpha$ image, can trace dusty
materials existing within the main outflow cavity. In particular, Br SW and Br
NE 1 detected near the cavity axis were found to show two separate Br$\gamma$
peaks, for which the association with the bipolar main outflow from MWC 1080A
was proposed in Section III.1.1. Br SW is one of the brightest Br$\gamma$
sources detected in our IGRINS observation and found to have a mid-IR
counterpart. Li et al. (2014) identified three prominent mid-IR features in
the vicinity of MWC 1080A, one of which (designated as “south finger” in their
Figure 2) is spatially coincident with Br SW although their 11.2 $\micron$
image showed no two separate peaks.

In Figure 13(b), the H$\alpha$ image of Figure 1(b) is overlaid on the [S II]
contours of Figures 8(b) and 12(a). We found that several H$\alpha$ features
show correlations with the [S II] HH objects. “Knot B” appears to have a
definite H$\alpha$ counterpart, and “Knot A’ also overlaps with a bright
H$\alpha$ region. The H$\alpha$ counterpart of “Knot B” is likely the
H$\alpha$ emission induced by “Outflow B.” The bright H$\alpha$ region
overlapping with “Knot A” is also likely related to “Outflow A” although the
scattered component of the stellar emission seems to be blended. In fact, in
Figure 13(a), the global H$\alpha$ morphology agrees well with the 13CO
boundaries, but the bright H$\alpha$ region near “Outflow A” is located inside
the SE 13CO region. For this region, the H$\alpha$ morphology follows the
distorted CS molecular boundary shown in Figure 14(a) much better. In Section
IV.1.2, we discussed the possibility of the actual association between
“Outflow A” and the distorted CS boundary based on the H2 1-0 S(1) channel
maps in Figure 14(a). The fact that this bright H$\alpha$ region is not
apparent in the 11.2 $\micron$ image of Li et al. (2014) (see their Figure 5)
also supports its origin in ionized hydrogen, rather than dust scattering. The
other [S II] HH objects (“Knot C” to “Knot F”) have no clear H$\alpha$
counterparts. However, “Knot D” and “Knot E” seem to be coincident with a
boundary of a bright H$\alpha$ region near the NE axis of the main outflow
cavity. If they are indeed related to the NE main outflow, as mentioned in
Sections III.2.1 and IV.1.1, then at least some H$\alpha$ fluxes of the bright
H$\alpha$ region could originate from ionized hydrogen possibly associated
with the NE main outflow.

As can be seen in Figure 13(b), the arc-like H$\alpha$ feature has no [S II]
counterpart, although “Knot C” lies close to it. This arc-like feature is seen
well in the red continuum filter rN image of Poetzel et al. (1992), but
disappears in their [S II]$-$rN image (see their Figures 7(b) and (d)). In
fact, this feature also appears in the IPHAS broad-band $r$\- and $i$-filter
images. Furthermore, we found the same feature in the PanSTARRS broad-band
$g$-, $r$-, and $i$-filter images.333https://ps1images.stsci.edu/cgi-
bin/ps1cutouts The presence of a similar arc-like feature in the continuum
over a wide wavelength range indicates that the arc shape found in H$\alpha$
is highly likely to be due to a reflection nebula that scatters stellar
H$\alpha$ emission. The weakness of the H2 and [Fe II] lines (H2/Fe NE cavity
edge in Figure 12(c)) also supports that shock excitation is not the main
cause of this feature. The spatial coincidence of the arc-like H$\alpha$
feature with the NE 13CO boundary, as shown in Figure 13(a), suggests that the
arc-like feature is produced by the illumination of starlight on a dusty
surface of the NE cavity edge formed by the main outflow from MWC 1080A.

In Figures 13(a) and (b), there also exist several H$\alpha$ features around
YSO 4 (the second masked-out star in the figure). However, they show no
correlations with the 13CO and [S II] morphologies. Because these features are
also seen clearly in the IPHAS and PanSTARRS broad-band continuum images, they
are likely due to dusty materials illuminated by stellar emission. The star
YSO 4 is one of the bright stars in the optical images of Poetzel et al.
(1992), designated as “star #2” in their image (see Figure 13(b)). It also
belongs to the NIR-identified young stars (Wang et al., 2008), as indicated by
a triangle in Figure 13(a). Therefore, if YSO 4 is another active young star
emitting a strong H$\alpha$ line, besides MWC 1080A, the extended H$\alpha$
features around it could be likely induced by YSO 4; of course, most of the
other H$\alpha$ reflection features seem to be illuminated by MWC 1080A.

In addition to the H$\alpha$ emission shown in Figures 13(a) and (b), we
identified a few more, faint H$\alpha$ features far away in the SW direction
from MWC 1080A, as indicated in Figure 1(b). As discussed in Sections IV.1.1
and IV.1.2, we associated some parts of them with the counter outflows
corresponding to the NE main outflow and “Knot B.” However, most of these
faint features can also be seen in the IPHAS and PanSTARRS broad-band images.
Therefore, they also likely trace the stellar H$\alpha$ emission scattered by
dust on surfaces of the cavities formed by the main outflow, “Outflow B,” and
other unknown outflows. Marston & McCollum (2008) reported a large, diffuse
lobe structure including most of the above faint H$\alpha$ features in their
own H$\alpha$ image (see their Figure 5(a)). They interpreted the large
H$\alpha$ lobe as a photoionized boundary of a cavity formed by outflows from
central stars. However, most parts of the lobe are also seen in the IPHAS and
PanSTARRS broad-band continuum images. This implies that the lobe structure is
likely to be caused by the light scattered on the dusty surfaces of the
cavity.

In order to clarify the origin of the extended H$\alpha$ emission in the MWC
1080 region, we made an H$\alpha$-to-continuum ratio map using the IPHAS
H$\alpha$\- and $r$-filter images, as shown in Figures 13(c) and (d). In
Figure 13(c), most areas are found to have ratios in a range of 1.5–2.5,
including the central region around MWC 1080A, the arc-like feature, the
bright features around YSO 4, the SW faint features, and the regions near the
axis of the main outflow. Only two small regions, near the heads of “Knot A”
and “Knot B”, appear to have ratios as high as 2.5–3.5, as can be seen more
clearly in Figure 13(d). In these regions, the H$\alpha$ emission would
originate dominantly from the stellar outflows (“Outflow A” and “Outflow B”),
rather than from dust scattering.

Finally, it is worth noting that the H2 fluorescent lines observed along the
surfaces of the main outflow cavity wall, as shown in Section III.2.1, imply
the presence of widespread UV photons (11.2 eV $<$ $h\nu$ $<$ 13.6 eV) within
the cavity. The Lyman-Werner radiation is likely to co-exist with Lyman
continuum photons ($h\nu$ $>$ 13.6 eV), suggesting that diffuse photo-ionized
hydrogen gas may also exist inside the main outflow cavity. However, we found
no clear signature for photo-ionized components in the analysis of the
hydrogen Brackett emission lines, which could be due to the dominant
scattering components in this region.

####  IV.2.2 Compact Emission

We identified the compact hydrogen line emissions (Br$\gamma$ and H$\alpha$)
in the three young stars MWC 1080A, MWC 1080E, and YSO 1. Their Br$\gamma$
line profiles were found to be broad ($\Delta V$ = 163, 235, and 234 km s-1,
respectively) and generally symmetric about the line center, except for the
central absorption feature (or the double-peaked profile) appearing in YSO 1.
The stellar hydrogen emission lines observed in young stars have been
associated with infalling accretion and/or outflowing winds (e.g., Najita et
al., 1996; Folha & Emerson, 2001; Kurosawa et al., 2006; Kraus et al., 2008;
Tambovtseva et al., 2016). Najita et al. (1996) reported broad (FWZI = 400–700
km s-1) and generally symmetric Br$\gamma$ line profiles from seven low-mass
YSOs. Even though two of those YSOs have P Cygni absorptions (blueshifted
absorptions) in their Balmer lines indicating outflowing winds, they suggested
that the Br$\gamma$ line emission arises from infalling accretion rather than
outflowing winds. Folha & Emerson (2001) observed the Br$\gamma$ line profiles
for 37 T Tauri stars and found that 72% of them have broad ($\Delta V$ =
100–300 km s-1) and generally symmetric Br$\gamma$ line profiles with no
strong absorption features. They suggested that those line profiles could be
partially explained by magnetospheric accretion models. Regarding the modeling
of the H$\alpha$ line emission from T Tauri stars, Kurosawa et al. (2006)
proposed hybrid models including both magnetospheric accretion and a disk
wind, which could reproduce a wide variety of types for the H$\alpha$ line
profiles observed in T Tauri stars. Kurosawa et al. (2006) found that
symmetric H$\alpha$ line profiles can appear at various inclination angles for
the circumstellar disk when the magnetospheric component is dominant. Although
there are no definitely-known spectral types for the young stars MWC 1080E and
YSO 1, they were classified as low-mass young stars by Wang et al. (2008) from
a NIR $K^{\prime}$-band image. If they are truly low-mass young stars, their
Br$\gamma$ emissions can be explained mainly by magnetospheric accretion. The
central absorption feature (or the double-peaked profile) in the Br$\gamma$
profile of YSO 1 may be caused by the disk wind component, as shown in the
model of Kurosawa et al. (2006) (see their Figures A1–A3).

If MWC 1080E and YSO 1 are the driving sources of the newly-identified
outflows in this study (“Outflow A” and “Outflow B”), as discussed in Section
IV.1.2, they would be massive young stars, considering the large distance to
the MWC 1080 system (1.373 $\pm$ 0.174 kpc, Gaia Collaboration, 2018). They
could belong to Herbig stars as MWC 1080A. Due to the weak magnetic fields
detected in Herbig stars, the magnetosphere is expected to be less developed
in Herbig stars than in low-mass young stars (Tambovtseva et al., 2014; Garcia
Lopez et al., 2016; Tambovtseva et al., 2016). By modeling the Br$\gamma$ line
emission from the magnetosphere, inner gaseous accretion disk, and disk wind
region of Herbig AeBe stars, Tambovtseva et al. (2016) showed that the disk
wind component is the most dominant contributor to the Br$\gamma$ line. Their
disk wind model shows that symmetric Br$\gamma$ line profiles appear in disks
viewed close to pole-on, whereas double-peaked profiles become prominent in
disks viewed closer to edge-on (see their Figure 1). They also suggested that
the component from the inner gaseous accretion disk can transform double-
peaked profiles into single-peaked (symmetric) ones when the gap between two
peaks is not large (see their Figure 8). The high-blueshift components
detected in the two outflows ($-$233 km s-1 [Fe II] in “Outflow A” and $-$156
km s-1 [S II] in “Outflow B,” see Section IV.1.2) indicate that the
corresponding circumstellar disks are not viewed close to edge-on. Therefore,
if MWC 1080E and YSO 1 are truly Herbig stars driving “Outflow A” and “Outflow
B,” the symmetric Br$\gamma$ line profile of MWC 1080E and the weakly double-
peaked profile of YSO 1 can be explained by dominant disk winds. For MWC
1080E, the contribution of an inner gaseous accretion disk might enhance the
symmetry of its profile.

On the other hand, MWC 1080A is expected to harbor a nearly edge-on
circumstellar disk, considering the low inclination angle of the main outflow,
as discussed in Section IV.1.1. To explain the symmetric and single-peaked
Br$\gamma$ line profile observed in the Herbig star VV Ser, which has a nearly
edge-on circumstellar disk, Garcia Lopez et al. (2016) added a bipolar outflow
component into a model with magnetospheric accretion and a disk wind. They
showed that the bipolar outflow could reproduce the single-peaked Br$\gamma$
line profile in an edge-on disk system. Therefore, the similar single-peaked
Br$\gamma$ line profile observed in MWC 1080A is also likely to be dominated
by a stellar wind producing a bipolar outflow. Yoshida et al. (1992) observed
prominent P Cygni absorptions and broad wings extending up to $\sim$1000 km
s-1 in the hydrogen Balmer lines of MWC 1080A and concluded that this Herbig
star has a strong stellar wind with a velocity of up to 1000 km s-1. Although
the Br$\gamma$ line of MWC 1080A observed in this study shows no P Cygni
absorption, the redshifted wing extending up to $\sim$300 km s-1, as seen in
Figure 3, could support the association with the stellar wind expected from
the Balmer lines. In addition, note that the close (0.$\arcsec$8) binary MWC
1080B of MWC 1080A was observed in the same IGRINS slit position. However, we
could not resolve the Br$\gamma$ line of MWC 1080B from that of MWC 1080A.
Judging from the more than an order of magnitude higher total luminosity of
MWC 1080A than that of MWC 1080B (Leinert et al., 1997), MWC 1080A could
mostly contribute to the observed Br$\gamma$ emission.

##  V. Summary and conclusions

We observed the MWC 1080 region by IGRINS with a high spectral resolution of
$\lambda$/$\Delta\lambda$ $\sim$45,000 and a broad wavelength coverage of the
NIR H (1.49–1.80 $\micron$) and K (1.96–2.46 $\micron$) bands. This study is
the first high-resolution NIR spectroscopic observation for the MWC 1080
region. From a total of ten slit positions, we detected six hydrogen Brackett
lines including Br$\gamma$ $\lambda$2.166 $\micron$, seven molecular hydrogen
lines including H2 1-0 S(1) $\lambda$2.122 $\micron$, and an [Fe II]
$\lambda$1.644 $\micron$ forbidden line. We identified several diffuse sources
in the Br$\gamma$, H2 1-0 S(1), and [Fe II] PVDs and analyzed the line
profiles and line ratios for the individual sources. From the obtained
kinematic and line ratio results, and also the morphological comparisons with
the H$\alpha$, [S II], 13CO, and CS maps, we found the following.

1\. Most of the diffuse Br$\gamma$ sources around MWC 1080A were found to be
dusty nebulae that scatter the Br$\gamma$ emission from MWC 1080A. Therefore,
the extended H$\alpha$ emission around MWC 1080A would also be predominantly
due to scattering by dust located on the surface of the main outflow cavity.
The Br$\gamma$ morphology close to MWC 1080A shows two separate peaks near the
axis of the main outflow (PA $\simeq$ 40$\arcdeg$), which may be due to dusty
materials related to the bipolar outflow from MWC 1080A. On the other hand,
two compact Br$\gamma$ sources close to the young stars MWC 1080E and YSO 1
were found to be direct Br$\gamma$ emissions from the corresponding stars;
this suggests that MWC 1080E and YSO 1 are highly likely young stars with
active accretion and/or winds.

2\. The H2 lines with $V_{\mathrm{centroid}}=$ $-$6 to +3 km s-1 near the
systemic LSR velocity and narrow $\Delta V$ of 9–19 km s-1 were detected in
the central region around MWC 1080A. Based on the line ratio analysis, we
identified them as fluorescent H2 lines. From the H2 1-0 S(1) velocity channel
maps, we revealed that the fluorescent H2 emission traces PDRs formed on the
front, limb, and rear surfaces of the main outflow cavity, and the cavity wall
with a cylindrical shape is expanding outward with a velocity of $\sim$10–15
km s-1. The observed H2 fluorescent lines seem to indirectly suggest the
presence of diffuse photo-ionized hydrogen gas inside the main outflow cavity.

3\. The H2 lines with slightly-blueshifted $V_{\mathrm{centroid}}$ of $-$12 to
$-$4 km s-1 and moderate $\Delta V$ of 22–24 km s-1 were detected along the NE
axis of the main outflow cavity. The line ratio analysis shows that they are
possibly thermal H2 lines. In particular, just inside an arc-like H$\alpha$
feature located at the NE cavity edge, the H2 line emission does peak together
with the shock-induced [Fe II] line emission with $V_{\mathrm{centroid}}$ =
$-$10 km s-1 and $\Delta V$ = 43 km s-1. This suggests that the H2 and [Fe II]
emissions could be induced by shock heating in the NE main outflow from MWC
1080A, although most parts of the arc-like H$\alpha$ feature were revealed to
be reflection nebulae scattering stellar H$\alpha$ emission. Low blueshifted
$V_{\mathrm{centroid}}$ for the [Fe II] line implies that the NE main outflow
from MWC 1080A is the blueshifted outflow with a low inclination angle with
respect to the sky plane. In addition, from the H$\alpha$ line image, we
interpreted a faint H$\alpha$ feature located in the opposite direction from
MWC 1080A as the SW cavity edge formed by the counter outflow corresponding to
the NE main outflow.

4\. The H2 lines with a blueshifted $V_{\mathrm{centroid}}$ of $-$31 to $-$10
km s-1 and a broad $\Delta V$ of 18–43 km s-1 were detected near/in the SE
molecular region. From the line ratio analysis, they were identified as
thermal H2 lines. Some of their components have strong spatial and kinematic
correlations with the shock-induced [Fe II] lines with a highly-blueshifted
$V_{\mathrm{centroid}}$ of $-$239 to $-$42 km s-1 and a broad $\Delta V$ of
77–139 km s-1, which can be explained by stellar outflow shocks and the
ambient molecular gas entrained by the shocks. Out of them, the brightest H2
and [Fe II] emissions were detected near the peak position of a [S II] HH
object, “Knot A.” Comparing double-velocity [Fe II] components detected here
with the bow shock model of Hartigan et al. (1987), we suggest that “Knot A”
is a high-velocity (a shock velocity of 300–400 km s-1) and highly-blueshifted
(an inclination angle of $>$45$\arcdeg$) outflow moving towards the SE
direction (referred to as “Outflow A” with PA $\simeq$ 135$\arcdeg$). We also
propose that some other [Fe II] and H2 components are possibly associated with
another [S II] HH object, “Knot B.” We found that there is another faint
H$\alpha$ feature in the direction of the SW counter outflow corresponding to
“Knot B” (referred to as “Outflow B” with PA $\simeq$ 77$\arcdeg$) and those
[Fe II] and H2 components lie near the axis of the outflow. In an
H$\alpha$-to-continuum ratio map, we confirmed that “Knot A” and “Knot B” have
inherent H$\alpha$ emissions excited by the outflows.

This study showed that atomic hydrogen line emissions observed in the MWC 1080
region mostly originate from the stellar emission of MWC 1080A scattered by
dust. However, the extended components originating from ionized gas related to
two stellar outflows and the compact components of two young stars were also
found. In conclusion, the H$\alpha$ nebulosity in the MWC 1080 region is
overall dominated by dust scattering of the stellar emission but locally by
shock-excited ionized gases, depending on locations. Our results demonstrate
the importance of high-resolution observations. The MWC 1080 region includes
at least $\sim$50 young stars. Therefore, there could possibly be more
outflows associated with young stars than we have found. In this study, we
identified at least three outflows from MWC 1080A and other young stars.
Further optical/NIR spectroscopic observations with a wider spatial coverage
over this region would enable us to find more unknown outflows and their
accurate driving sources.

We thank the anonymous referee for useful comments that helped to improve the
manuscript. This work was supported by the National Research Foundation of
Korea (NRF) grant funded by the Korea government (MSIT) (No.
2019R1F1A1064112). This work used the Immersion Grating Infrared Spectrograph
(IGRINS) that was developed under a collaboration between the University of
Texas at Austin and the Korea Astronomy and Space Science Institute (KASI)
with the financial support of the US National Science Foundation under grant
AST-1229522, of the University of Texas at Austin, and of the Korean GMT
Project of KASI. These results made use of the Lowell Discovery Telescope
(LDT) at Lowell Observatory. Lowell is a private, non-profit institution
dedicated to astrophysical research and public appreciation of astronomy and
operates the LDT in partnership with Boston University, the University of
Maryland, the University of Toledo, Northern Arizona University and Yale
University. This paper makes use of data obtained as part of the IPHAS
(http://www.iphas.org/) carried out at the Isaac Newton Telescope (INT). This
research has made use of the SIMBAD database, operated at CDS, Strasbourg,
France.

##  Appendix A IGRINS Observations of Additional Slit Positions

Figure 14.— (a) H2 1-0 S(1) and (b) [Fe II] velocity channel maps around the
SE molecular region, which are overlaid on the CS (Wang et al., 2008) and [S
II] (Poetzel et al., 1992) contours, respectively. The color scales are all in
units of the detection significance (signal/$\sigma$). The data obtained from
additional observations for twelve slit positions were overplotted together
with the results of the slit positions S1-S10 (denoted by the rectangles). For
the overlapped regions, the S1-S10 data were used because they have better
data quality. The integrated velocity range is indicated at the top of each
channel map. Red dashed circles (young stars) and yellow+red lines (axes of
the main outflow, “Outflow A,” and “Outflow B”) are the same as in Figure 1.
Here, the yellow and red lines represent the blueshifted and redshifted part
of the outflows, respectively.

We also carried out additional observations for twelve slit positions with
IGRINS to confirm the origins of the [Fe II] and H2 emissions detected near
the SE molecular region. Although the results were not very useful because of
bad weather conditions, we plotted the H2 1-0 S(1) and [Fe II] velocity
channel maps in Figure 14 to see rough shapes of distributions of the H2 and
[Fe II] emissions. The H2 1-0 S(1) and [Fe II] maps were overlaid on the CS
molecular and [S II] contours, respectively. The CS and [S II] contours were
adapted from Figure 3(b) of Wang et al. (2008) and Figure 8(d) of Poetzel et
al. (1992), respectively.

## References

  * Alonso-Albi et al. (2009) Alonso-Albi, T., Fuente, A., Bachiller, R., et al. 2009, A&A, 497, 117
  * Barentsen et al. (2014) Barentsen, G., Farnhill, H. J., Drew, J. E., et al. 2014, MNRAS, 444, 3230
  * Berriman et al. (2003) Berriman, G. B., Good, J. C., Curkendall, D. W., et al. 2003, in ASP Conf. Ser. 295, Astronomical Data Analysis Software and Systems XII, ed. H. E. Payne, R. I. Jedrzejewski, & R. N. Hook (San Francisco, CA: ASP), 343
  * Black & van Dishoeck (1987) Black, J. H., & van Dishoeck, E. F. 1987, ApJ, 322, 412
  * Cantó et al. (1984) Cantó, J., Rodríguez, L. F., Calvet, N., & Levreault, R. M. 1984, ApJ, 282, 631
  * Cardelli et al. (1989) Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245
  * Cohen & Kuhi (1979) Cohen M., & Kuhi L., 1979, ApJS, 41, 743
  * Curiel et al. (1989) Curiel, S., Rodríguez, L. F., Cantó, J., et al. 1989, Astrophysical Letters and Communications, 27, 299
  * Davis et al. (2001) Davis, C. J., Ray, T. P., Desroches, L., & Aspin, C. 2001, MNRAS, 326, 524
  * Davis et al. (2003) Davis, C. J., Whelan, E., Ray, T. P., & Chrysostomou, A. 2003, A&A, 397, 693
  * Drew et al. (2005) Drew, J. E., Greimel, R., Irwin, M. J., et al. 2005, MNRAS, 362, 753
  * Folha & Emerson (2001) Folha, D. F., & Emerson, J. P. 2001, A&A, 365, 90
  * Fuente et al. (2003) Fuente, A., Rodríguez-Franco, A., Testi, L., et al. 2003, ApJ, 598, L39
  * Gaia Collaboration (2018) Gaia Collaboration 2018, yCat, 1345, 0
  * Garcia Lopez et al. (2016) Garcia Lopez, R., Kurosawa, R., Caratti o Garatti, A., et al. 2016, MNRAS, 456, 156
  * Girart et al. (2002) Girart, J. M., Curiel, S., Rodríguez, L. F., & Cantó, J. 2002, RevMexAA, 38, 169
  * González-Solares et al. (2008) González-Solares, E. A., Walton, N. A., Greimel, R., et al. 2008, MNRAS, 388, 89
  * Hartigan et al. (1987) Hartigan, P., Raymond, J., & Hartmann, L. 1987, ApJ, 316, 323
  * Harvey et al. (1979) Harvey, P. M., Thronson, H. A., & Gatley, I. 1979, ApJ, 231, 115
  * Herbig (1960) Herbig, G. H. 1960, ApJS, 4, 337
  * Hillenbrand et al. (1992) Hillenbrand L. A., Strom S. E., Vrba F. J., & Keene J., 1992, ApJ, 397, 613
  * Jacob et al. (2010) Jacob, J. C., Katz, D. S., Berriman, G. B., et al. 2010, Montage: An Astronomical Image Mosaicking Toolkit, Astrophysics Source Code Library, ascl:1010.036
  * Kaplan et al. (2017) Kaplan, K. F., Dinerstein, H. L., Oh, H., et al. 2017, ApJ, 838, 152
  * Kim et al. (2018) Kim, I.-J., Pyo, J., Jeong, W.-S., et al. 2018, ApJS, 238, 28
  * Kraus et al. (2008) Kraus, S., Hofmann, K.-H., Benisty, M., et al. 2008, A&A, 489, 1157
  * Kurosawa et al. (2006) Kurosawa, R., Harries, T. J., & Symington, N. H. 2006, MNRAS, 370, 580
  * Lee et al. (2017) Lee, J.-J., Gullikson, K., & Kaplan, K. 2017, igrins/plp 2.2.0. Zenodo. http://doi.org/10.5281/zenodo.845059
  * Leinert et al. (1997) Leinert, C., Richichi, A., & Haas, M. 1997, A&A, 318, 472
  * Li et al. (2014) Li, D., Mariñas, N., & Telesco, C. M. 2014, ApJ, 796, 74
  * Mace et al. (2018) Mace, G., Sokal, K., Lee, J.-J., et al. 2018, Proc. SPIE, 10702, 107020Q
  * Marston & McCollum (2008) Marston, A. P., & McCollum, B. 2008, A&A, 193, 202
  * Najita et al. (1996) Najita, J., Carr, J. S., & Tokunaga, A. T. 1996, ApJ, 456, 292
  * Oh et al. (2016a) Oh, H., Pyo, T.-S., Kaplan, K., et al. 2016a, ApJ, 833, 275
  * Oh et al. (2016b) Oh, H., Pyo, T.-S., Yuk, I.-S., et al. 2016b, ApJ, 817, 148
  * Oudmaijer et al. (1997) Oudmaijer, R. D., Busfield, G., & Drew, J. E. 1997, MNRAS, 291, 797
  * Park et al. (2014) Park, C., Jaffe, D. T., Yuk, I.-S., et al. 2014, Proc. SPIE, 9147, 91471D
  * Poetzel et al. (1992) Poetzel, R., Mundt, R., & Ray, T. P. 1992, A&A, 262, 229
  * Polomski et al. (2002) Polomski, E. F., Telesco, C. M., Piña, R., & Schulz, B. 2002, AJ, 124, 2207
  * Pyo et al. (2002) Pyo, T.-S., Hayashi, M., Kobayashi, N., et al. 2002, ApJ, 570, 724
  * Rousselot et al. (2000) Rousselot, P., Lidman, C., Cuby, J.-G., Moreels, G., & Monnet, G. 2000, A&A, 354, 1134
  * Sandell et al. (2011) Sandell, G., Weintraub, D. A., & Hamidouche, M. 2011, ApJ, 727, 26
  * Storey & Hummer (1995) Storey, P. J., & Hummer, D. G. 1995, MNRAS, 272, 41
  * Takami et al. (2006) Takami, M., Chrysostomou, A., Ray, T. P., et al. 2006, ApJ, 641, 357
  * Tambovtseva et al. (2014) Tambovtseva, L. V., Grinin, V. P., & Weigelt, G., 2014, A&A, 562, A104
  * Tambovtseva et al. (2016) Tambovtseva, L. V., Grinin, V. P., & Weigelt, G., 2016, A&A, 590, A97
  * Tanaka et al. (1989) Tanaka, M., Hasegawa, T., Hayashi, S. S., Brand, P. W. J. L., & Gatley, I. 1989, ApJ, 336, 207
  * Wang et al. (2008) Wang, S., Looney, L. W., Brandner, W., & Close, L. M. 2008, ApJ, 673, 315
  * Wolniewicz et al. (1998) Wolniewicz, L., Simbotin, I., & Dalgarno, A. 1998, ApJS, 115, 293
  * Wouterloot & Brand (1989) Wouterloot, J. G. A., & Brand, J. 1989, A&AS, 80, 149
  * Yoshida et al. (1992) Yoshida, S., Kogure, T., Nakano, M., Tatematsu, K., & Wiramihardja, S. D. 1992, PASJ, 44, 77
  * Yuk et al. (2010) Yuk, I.-S., Jaffe, D. T., Barnes, S., et al. 2010, Proc. SPIE, 7735, 77351M

Table 1Line Profiles and Fluxes for Br$\gamma$ Sources and MWC 1080A

|  |  | Extended Sources |  | Compact Sources
---|---|---|---|---|---
Line |  $\lambda$ ($\micron$) |  | Br SW | Br NW | Br SE | Br NE 1 | Br NE 2 | MWC 1080A | Br 1080E | Br YSO 1
|  |  $\mathnormal{V}_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$6 $\pm$ 1 |  $-$2 $\pm$ 1 |  $-$10 $\pm$ 1 |  $-$10 $\pm$ 1 |  $-$11 $\pm$ 1 |  $-$8 $\pm$ 1 | 8 $\pm$ 1 |  $-$11 $\pm$ 2
Br$\gamma$ | 2.16612 |  $\Delta\mathnormal{V}$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 162 $\pm$ 1 | 171 $\pm$ 2 | 151 $\pm$ 2 | 165 $\pm$ 3 | 153 $\pm$ 2 | 163 $\pm$ 2 | 235 $\pm$ 2 | 234 $\pm$ 10
|  |  $\mathnormal{F}/\mathnormal{F}_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the Br$\gamma$ line flux $F_{0}$ that is displayed in Figure 3. | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.02 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.18
|  |  $\mathnormal{V}_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$19 $\pm$ 1 |  $-$6 $\pm$ 2 |  $-$18 $\pm$ 1 |  $-$30 $\pm$ 2 |  $-$16 $\pm$ 1 |  $-$14 $\pm$ 1 |  $-$4 $\pm$ 2 |  $\cdots$
Br 10 | 1.73669 |  $\Delta\mathnormal{V}$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 140 $\pm$ 2 | 160 $\pm$ 6 | 123 $\pm$ 3 | 161 $\pm$ 5 | 148 $\pm$ 3 | 130 $\pm$ 2 | 262 $\pm$ 7 |  $\cdots$
|  |  $\mathnormal{F}/\mathnormal{F}_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the Br$\gamma$ line flux $F_{0}$ that is displayed in Figure 3. | 0.56 $\pm$ 0.01 | 0.45 $\pm$ 0.04 | 0.51 $\pm$ 0.01 | 0.59 $\pm$ 0.04 | 0.60 $\pm$ 0.01 | 0.45 $\pm$ 0.00 | 0.28 $\pm$ 0.02 |  $\cdots$
|  |  $\mathnormal{V}_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$23 $\pm$ 1 |  $-$21 $\pm$ 2 |  $-$22 $\pm$ 1 |  $-$29 $\pm$ 2 |  $-$27 $\pm$ 1 |  $-$14 $\pm$ 1 |  $-$12 $\pm$ 2 |  $\cdots$
Br 11 | 1.68111 |  $\Delta\mathnormal{V}$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 141 $\pm$ 2 | 178 $\pm$ 6 | 146 $\pm$ 3 | 194 $\pm$ 6 | 149 $\pm$ 2 | 146 $\pm$ 1 | 216 $\pm$ 6 |  $\cdots$
|  |  $\mathnormal{F}/\mathnormal{F}_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the Br$\gamma$ line flux $F_{0}$ that is displayed in Figure 3. | 0.44 $\pm$ 0.01 | 0.46 $\pm$ 0.04 | 0.63 $\pm$ 0.01 | 0.59 $\pm$ 0.05 | 0.67 $\pm$ 0.01 | 0.43 $\pm$ 0.00 | 0.17 $\pm$ 0.01 |  $\cdots$
|  |  $\mathnormal{V}_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$10 $\pm$ 1 |  $\cdots$ |  $-$20 $\pm$ 3 |  $-$31 $\pm$ 4 |  $-$10 $\pm$ 2 |  $-$14 $\pm$ 1 |  $-$14 $\pm$ 4 |  $\cdots$
Br 12 | 1.64117 |  $\Delta\mathnormal{V}$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 140 $\pm$ 3 |  $\cdots$ | 115 $\pm$ 8 | 227 $\pm$ 11 | 177 $\pm$ 5 | 145 $\pm$ 2 | 292 $\pm$ 10 |  $\cdots$
|  |  $\mathnormal{F}/\mathnormal{F}_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the Br$\gamma$ line flux $F_{0}$ that is displayed in Figure 3. | 0.37 $\pm$ 0.01 |  $\cdots$ | 0.23 $\pm$ 0.05 | 0.61 $\pm$ 0.14 | 0.54 $\pm$ 0.03 | 0.37 $\pm$ 0.00 | 0.22 $\pm$ 0.03 |  $\cdots$
|  |  $\mathnormal{V}_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$13 $\pm$ 2 | 1 $\pm$ 4 |  $-$7 $\pm$ 3 |  $\cdots$ |  $-$13 $\pm$ 3 |  $-$15 $\pm$ 1 |  $\cdots$ |  $\cdots$
Br 13 | 1.61137 |  $\Delta\mathnormal{V}$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 161 $\pm$ 5 | 159 $\pm$ 11 | 134 $\pm$ 8 |  $\cdots$ | 107 $\pm$ 8 | 131 $\pm$ 2 |  $\cdots$ |  $\cdots$
|  |  $\mathnormal{F}/\mathnormal{F}_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the Br$\gamma$ line flux $F_{0}$ that is displayed in Figure 3. | 0.45 $\pm$ 0.02 | 0.30 $\pm$ 0.09 | 0.30 $\pm$ 0.06 |  $\cdots$ | 0.25 $\pm$ 0.07 | 0.29 $\pm$ 0.00 |  $\cdots$ |  $\cdots$
|  |  $\mathnormal{V}_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$13 $\pm$ 1 |  $-$21 $\pm$ 3 |  $-$15 $\pm$ 2 |  $-$12 $\pm$ 2 |  $-$13 $\pm$ 2 |  $-$16 $\pm$ 1 | 8 $\pm$ 4 |  $\cdots$
Br 14 | 1.58849 |  $\Delta\mathnormal{V}$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 134 $\pm$ 3 | 201 $\pm$ 7 | 141 $\pm$ 5 | 172 $\pm$ 6 | 161 $\pm$ 5 | 158 $\pm$ 2 | 218 $\pm$ 12 |  $\cdots$
|  |  $\mathnormal{F}/\mathnormal{F}_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the Br$\gamma$ line flux $F_{0}$ that is displayed in Figure 3. | 0.28 $\pm$ 0.01 | 0.42 $\pm$ 0.05 | 0.37 $\pm$ 0.02 | 0.43 $\pm$ 0.04 | 0.35 $\pm$ 0.02 | 0.34 $\pm$ 0.00 | 0.07 $\pm$ 0.02 |  $\cdots$

Note. — The line profiles and fluxes of Br 10–14 were calculated by the same
method as used for Br$\gamma$ (see Figure 3), and the lines measured with
$\geq$3$\sigma$ significance (based on the line flux) are presented. For Br
YSO 1, only the Br$\gamma$ emission component was detected at a significance
level of $\geq$3$\sigma$. All of the line fluxes were not corrected for the
reddening effect.

Table 2Line Profiles and Fluxes for H2 Sources: Narrow Components

Line |  $\lambda$ ($\micron$) |  | H2 SW-E | H2 SW-W | H2 NW | H2 SE | H2 NE 1 | H2 knot A | H2 knot B | H2 YSO 2 | H2 NE 2 | H2 NE cavity axis
---|---|---|---|---|---|---|---|---|---|---|---|---
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$5 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$5 $\pm$ 0 | 0 $\pm$ 0 |  $-$9 $\pm$ 0 | 5 $\pm$ 0 | 1 $\pm$ 0 |  $-$5 $\pm$ 1 | 8 $\pm$ 1
H2 1-0 S(2) | 2.03376 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 12 $\pm$ 1 | 9 $\pm$ 0 | 11 $\pm$ 0 | 13 $\pm$ 1 | 19 $\pm$ 1 | 17 $\pm$ 1 | 10 $\pm$ 0 | 13 $\pm$ 1 | 20 $\pm$ 2 | 15 $\pm$ 1
|  |  $F/F_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the H2 1-0 S(1) line flux $F_{0}$ that is displayed in Figure 6. | 0.44 $\pm$ 0.02 | 0.40 $\pm$ 0.00 | 0.32 $\pm$ 0.00 | 0.51 $\pm$ 0.02 | 0.41 $\pm$ 0.01 | 0.36 $\pm$ 0.01 | 0.49 $\pm$ 0.00 | 0.58 $\pm$ 0.02 | 0.37 $\pm$ 0.04 | 0.64 $\pm$ 0.04
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$5 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$6 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$10 $\pm$ 0 | 3 $\pm$ 0 | 1 $\pm$ 0 |  $-$6 $\pm$ 0 | 9 $\pm$ 0
H2 1-0 S(1) | 2.12183 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 9 $\pm$ 0 | 10 $\pm$ 0 | 11 $\pm$ 0 | 11 $\pm$ 0 | 19 $\pm$ 1 | 18 $\pm$ 0 | 11 $\pm$ 0 | 11 $\pm$ 0 | 19 $\pm$ 1 | 14 $\pm$ 1
|  |  $F/F_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the H2 1-0 S(1) line flux $F_{0}$ that is displayed in Figure 6. | 1.00 $\pm$ 0.00 | 1.00 $\pm$ 0.00 | 1.00 $\pm$ 0.00 | 1.00 $\pm$ 0.00 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.00 | 1.00 $\pm$ 0.00 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.01 | 1.00 $\pm$ 0.02
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$5 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$1 $\pm$ 0 |  $-$5 $\pm$ 0 |  $-$2 $\pm$ 1 |  $-$9 $\pm$ 0 | 4 $\pm$ 0 | 1 $\pm$ 0 |  $-$7 $\pm$ 0 | 8 $\pm$ 1
H2 1-0 S(0) | 2.22329 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 11 $\pm$ 1 | 10 $\pm$ 1 | 10 $\pm$ 1 | 12 $\pm$ 1 | 18 $\pm$ 2 | 20 $\pm$ 1 | 12 $\pm$ 0 | 11 $\pm$ 1 | 10 $\pm$ 1 | 12 $\pm$ 3
|  |  $F/F_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the H2 1-0 S(1) line flux $F_{0}$ that is displayed in Figure 6. | 0.55 $\pm$ 0.01 | 0.53 $\pm$ 0.01 | 0.45 $\pm$ 0.02 | 0.71 $\pm$ 0.01 | 0.59 $\pm$ 0.06 | 0.26 $\pm$ 0.01 | 0.58 $\pm$ 0.00 | 0.90 $\pm$ 0.01 | 0.37 $\pm$ 0.01 | 0.32 $\pm$ 0.09
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$4 $\pm$ 0 |  $-$3 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$4 $\pm$ 1 | 1 $\pm$ 1 |  $-$12 $\pm$ 0 | 4 $\pm$ 0 | 2 $\pm$ 1 |  $\cdots$ |  $\cdots$
H2 2-1 S(1) | 2.24772 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 10 $\pm$ 1 | 10 $\pm$ 2 | 12 $\pm$ 1 | 10 $\pm$ 2 | 23 $\pm$ 2 | 20 $\pm$ 1 | 11 $\pm$ 1 | 14 $\pm$ 1 |  $\cdots$ |  $\cdots$
|  |  $F/F_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the H2 1-0 S(1) line flux $F_{0}$ that is displayed in Figure 6. | 0.45 $\pm$ 0.01 | 0.31 $\pm$ 0.03 | 0.24 $\pm$ 0.00 | 0.27 $\pm$ 0.03 | 0.41 $\pm$ 0.03 | 0.15 $\pm$ 0.00 | 0.37 $\pm$ 0.01 | 0.41 $\pm$ 0.02 |  $\cdots$ |  $\cdots$
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$4 $\pm$ 0 |  $-$1 $\pm$ 0 |  $-$1 $\pm$ 0 |  $-$4 $\pm$ 0 |  $-$3 $\pm$ 0 |  $-$11 $\pm$ 0 | 4 $\pm$ 0 | 0 $\pm$ 0 |  $-$7 $\pm$ 0 | 8 $\pm$ 0
H2 1-0 Q(1) | 2.40659 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 10 $\pm$ 1 | 9 $\pm$ 0 | 10 $\pm$ 0 | 9 $\pm$ 0 | 16 $\pm$ 1 | 21 $\pm$ 1 | 12 $\pm$ 0 | 10 $\pm$ 0 | 10 $\pm$ 1 | 9 $\pm$ 1
|  |  $F/F_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the H2 1-0 S(1) line flux $F_{0}$ that is displayed in Figure 6. | 1.62 $\pm$ 0.02 | 2.08 $\pm$ 0.00 | 2.13 $\pm$ 0.00 | 1.57 $\pm$ 0.01 | 1.41 $\pm$ 0.01 | 1.06 $\pm$ 0.01 | 1.43 $\pm$ 0.00 | 1.82 $\pm$ 0.01 | 1.21 $\pm$ 0.02 | 0.75 $\pm$ 0.05
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$6 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$3 $\pm$ 0 |  $-$5 $\pm$ 0 |  $-$10 $\pm$ 1 | 4 $\pm$ 0 | 0 $\pm$ 0 |  $\cdots$ |  $\cdots$
H2 1-0 Q(2) | 2.41344 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 11 $\pm$ 1 | 9 $\pm$ 1 | 10 $\pm$ 0 | 10 $\pm$ 2 | 13 $\pm$ 1 | 20 $\pm$ 2 | 11 $\pm$ 1 | 13 $\pm$ 1 |  $\cdots$ |  $\cdots$
|  |  $F/F_{0}$ccThe line flux $F$ was obtained from the Gaussian fitting and then normalized to the H2 1-0 S(1) line flux $F_{0}$ that is displayed in Figure 6. | 0.52 $\pm$ 0.04 | 0.61 $\pm$ 0.01 | 0.58 $\pm$ 0.01 | 0.60 $\pm$ 0.06 | 0.66 $\pm$ 0.03 | 0.39 $\pm$ 0.05 | 0.63 $\pm$ 0.02 | 0.99 $\pm$ 0.05 |  $\cdots$ |  $\cdots$
|  |  $V_{\mathrm{centroid}}$aaThe centroid velocity $V_{\mathrm{centroid}}$ obtained from the Gaussian fitting. (km s-1) |  $-$4 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$2 $\pm$ 0 |  $-$5 $\pm$ 1 |  $-$3 $\pm$ 1 |  $-$10 $\pm$ 0 | 3 $\pm$ 0 | 0 $\pm$ 0 |  $-$9 $\pm$ 1 | 9 $\pm$ 1
H2 1-0 Q(3) | 2.42373 |  $\Delta V$bbThe FWHM velocity width $\Delta V$ obtained from the Gaussian fitting. (km s-1) | 11 $\pm$ 1 | 13 $\pm$ 1 | 12 $\pm$ 0 | 13 $\pm$ 3 | 17 $\pm$ 1 | 19 $\pm$ 1 | 14 $\pm$ 1 | 7 $\pm$ 1 | 19 $\pm$ 2 | 10 $\pm$ 1