# An Analysis of AGN-Driven Outflows in the Seyfert 1 Galaxy NGC 3227

Julia Falcone Department of Physics and Astronomy, Georgia State University,
25 Park Place, Atlanta, GA 30303, USA  D. Michael Crenshaw Department of
Physics and Astronomy, Georgia State University, 25 Park Place, Atlanta, GA
30303, USA  Travis C. Fischer AURA for ESA, Space Telescope Science Institute,
3700 San Martin Drive, Baltimore, MD 21218, USA  Beena Meena Space Telescope
Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA  Mitchell
Revalski Space Telescope Science Institute, 3700 San Martin Drive, Baltimore,
MD 21218, USA  Maura Kathleen Shea Department of Physics and Astronomy,
Georgia State University, 25 Park Place, Atlanta, GA 30303, USA  Rogemar A.
Riffel Departamento de Física, CCNE, Universidade Federal de Santa Maria,
97105-900 Santa Maria, RS, Brazil  Zo Chapman College of Computer Science,
Georgia Institute of Technology, 266 Ferst Drive, Atlanta, GA 30332, USA
Nicolas Ferree Department of Physics, Stanford University, 382 Via Pueblo
Mall, Stanford, CA 94305, USA  Jacob Tutterow Department of Physics and
Astronomy, Georgia State University, 25 Park Place, Atlanta, GA 30303, USA
Madeline Davis Department of Physics and Astronomy, College of Charleston, 66
George Street, Charleston, SC 29424, USA

###### Abstract

We have characterized the ionized, neutral, and warm molecular gas kinematics
in the Seyfert 1 galaxy NGC 3227 using observations from the Hubble Space
Telescope Space Telescope Imaging Spectrograph, Apache Point Observatory’s
Kitt Peak Ohio State Multi-Object Spectrograph, Gemini-North’s Near-Infrared
Integral Field Spectrometer, and the Atacama Large Millimeter Array. We fit
multiple Gaussians to several spatially-resolved emission lines observed with
long-slit and integral-field spectroscopy and isolate the kinematics based on
apparent rotational and outflowing motions. We use the kinematics to determine
an orientation for the bicone along which the outflows travel, and find that
the biconical structure has an inclination of $40^{+5}_{-4}$° from our line of
sight, and a half-opening angle with an inner and outer boundary of
$47^{+6}_{-2}$°and $68^{+1}_{-1}$°, respectively. We observe ionized outflows
traveling 500 km s-1 at distances up to 7′′ (800 pc) from the SMBH, and
disturbed ionized gas up to a distance of 15′′ (1.7 kpc). Our analysis reveals
that the ionized outflows are launched from within 20 pc of the SMBH, at the
same location as a bridge of cold gas across the nucleus detected in ALMA
CO(2-1) observations. We measure a turnover radius where the gas starts
decelerating at a distance of $26\pm 6$ pc from the AGN. Compared to a
turnover radius in the range of $31-63$ pc from a radiative driving model, we
confirm that radiative driving is the dominant acceleration mechanism for the
narrow line region (NLR) outflows in NGC 3227.

Active galactic nuclei (16) – AGN host galaxies (2017) – Seyfert galaxies
(1447) – Emission line galaxies (459) – Galaxy winds (626) – Galaxy kinematics
(602) – Supermassive black holes (1663)

##  1 Introduction

At the core of every massive galaxy likely lies a supermassive black hole
(SMBH), which has a mass of $10^{5}-10^{9}$ M⊙. While we observe most SMBHs to
be rather quiescent in the nearby Universe, a minority (5$-$10%) of galaxies
possess AGN, wherein the central SMBHs are actively accreting matter and
gaining mass from a surrounding accretion disk. Beyond the accretion disk lies
a torus of dusty gas that can obscure our vision of the central AGN, depending
on its orientation relative to our line of sight (LOS), i.e. unobscured in
Type 1, obscured in Type 2 AGN. As matter falls from the accretion disk into
the SMBH, dynamical interactions between the infalling matter and a loss of
potential energy result in the release of massive amounts of radiation. This
radiation spans the entire electromagnetic spectrum, often rivaling its host
galaxy in brightness.

We utilize our understanding of the AGN kinematics to examine AGN feedback, by
which energy and momentum ejected from the nuclear region are deposited into
the interstellar medium and incorporated into outflowing material. These
outflows are accelerated by AGN radiation pressure and/or magnetic fields
(Fabian, 2012), and can result in the expulsion and heating of large
quantities of gas, thereby limiting and potentially truncating star formation
in the galaxy (Fischer et al., 2017, 2018; Revalski et al., 2021; Venturi et
al., 2021). Thus we can observe the relationship between the transportation of
outflowing material, known as AGN winds (Fabian, 2012), and its effects on
surrounding matter, known as AGN feedback. The impact that an AGN feedback
cycle can have on the AGN and its host galaxy can be substantial (Booth &
Schaye, 2009; Anglés-Alcázar et al., 2017) and is associated with the
regulation of SMBH accretion, galaxy evolution, and potentially both star
formation cessations and bursts (Piotrowska et al., 2021). Kinematic and
geometric models of observations show that the ionized AGN-driven winds flow
outward along a biconical geometry, with the central vertex of the bicone
intersecting the AGN (Antonucci & Miller, 1985; Pedlar et al., 1993; Nelson et
al., 2000; Pogge, 1988; Fischer et al., 2013). Spectroscopic subarcsecond
observations of the AGN’s narrow-line region (NLR) showing blueshifted and
redshifted emission allow us to determine the orientation of the cones
pointing toward and away from us (Fischer et al., 2013). These outflows are
often observed in the UV (Crenshaw & Kraemer, 2005; Crenshaw et al., 2009),
X-ray (Trindade Falcão et al., 2021a; Breedt et al., 2010), optical (Colbert
et al., 1996; Fischer et al., 2013), and IR wavelengths (Fischer et al., 2017;
Storchi-Bergmann et al., 2010; Riffel et al., 2023; U et al., 2022).

Many of these observations focus on Seyfert galaxies, which refer to a
relatively moderate bolometric luminosity ($L_{bol}\approx 10^{43}-10^{45}$
erg s-1), nearby ($z\leq 0.1$) subset of AGN. The Seyfert 1 and Seyfert 2
subclassifications are essential for further characterizing the AGN based on
the presence of broad-line and narrow- line regions (Khachikian & Weedman,
1974). The broad-line region (BLR) consists of dense clouds of ionized gas
($\mathrm{n_{H}=10^{8}-10^{12}}$ cm-3) a few light days ($\approx$ 0.005 pc)
from the SMBH. Beyond the BLR lies the narrow-line region (NLR), which can
extend to a few kpc from the AGN and is composed of significantly more diffuse
gas ($\mathrm{n_{H}\leq 10^{6}}$ cm-3; Revalski et al., 2022). These two
regions can be spectroscopically differentiated by observing the emitted
lines: the BLR is characterized by the presence of broadened permitted lines
because the enormous gravitational influence of the SMBH accelerates the gas
to extraordinary velocities. As a result, the emission line becomes
significantly Doppler broadened (full width at half maximum [FWHM] = 800 $-$
8000 km s-1). By contrast, the NLR contains both permitted and forbidden line
transitions and moves at slower speeds due to its farther distance from the
SMBH (FWHM $\leq$ 300 km s-1 for rotating gas, but can be as high as 2000 km
s-1 for outflowing gas; Fischer et al., 2018).

Seyfert 1 galaxies have torii oriented in a face-on direction relative to us
so that we see “down the barrel” to observe both the NLR and the BLR. By
contrast, the orientation of the torii obscures the central engine in Seyfert
2 galaxies in the optical regime, blocking our view of the BLR and resulting
in the observation of only the NLR (Antonucci, 1993).

Figure 1: Left: $7.8\arcmin\times 7.8\arcmin$ optical image of NGC 3227
(center) and NGC 3226 (top right) taken by the Sloan Digital Sky Survey (SDSS)
with ugriz filters. The white square shows the position of the WFC3 images.
The blue rectangles show the positions of the APO KOSMOS slits, and the
outline of the HST STIS slits are shown in black. Right: a continuum-
subtracted $9.5\arcsec\times 9.5\arcsec$ HST WFC3 F502N image of the nucleus,
which shows small-scale structure in the form of [O III] $\lambda$5007
emission. The pink square shows the position of the NIFS field of view. The
blue rectangles again show the KOSMOS slits, while the green rectangles give
greater detail for the positions of the STIS slits. The seven green parallel
STIS slits use the G750M filter, while the slightly tilted green slit uses the
G430L filter. The outermost G750M slits are labeled, and the inner slit
numbers increase accordingly. The black star shows the location of the bright
Seyfert 1 continuum source (i.e., the AGN).

###  1.1 NGC 3227

NGC 3227 ($z$ = 0.003859, pictured in Figure 1) is a Seyfert 1, SAB(s)a type
galaxy (deVaucouleurs et al., 1991). It is located in the constellation Leo at
a distance of $23.7\pm 2.6$ Mpc (Tonry et al., 2001; Blakeslee et al., 2001)
so that its transverse scale corresponds to $\sim$115 pc arcsec-1 on the plane
of the sky. NGC 3227 has a complex dynamical history through its interactions
with its companion NGC 3226. Rubin & Ford (1968) documented the galaxy pair in
depth, using long-slit spectroscopy to identify nuclear gas outflows and an
arm extending from NGC 3227 to NGC 3226 at a mean velocity of 550 km s-1 with
respect to the NGC 3227/3226 system. Mundell et al. (1995) followed up with
neutral H I imaging to detect two tidal tails on NGC 3227, one of which
extends $\sim$70 kpc northward towards and beyond NGC 3226, and the other
extending $\sim$30 kpc southward. They also discovered J1023+1952, an H I-rich
dwarf galaxy about $40^{\prime\prime}$ wide located in front of the western
side of NGC 3227’s disk.

Instru- | Program | Observation | Date | Grating/ | Exposure | Wavelength | Spectral | Spatial | Position | Spatial
---|---|---|---|---|---|---|---|---|---|---
ment | ID | or Program | (UT) | Filter/ | Time | Range | Dispersion | Scale | Angle | Offset
|  | ID |  | Grism | (s) | (Å) | (Å/pix) |  (′′/pix) | (deg) |  (′′ NW)
STIS | 7403 | O57204010 | 1999 Jan 31 | G750M | 2105 | $6248-6912$ | 0.56 | 0.051 | -137.62 | -0.75
STIS | 7403 | O57204020 | 1999 Jan 31 | G750M | 1600 | $6248-6912$ | 0.56 | 0.051 | -137.62 | -0.5
STIS | 7403 | O57204030 | 1999 Jan 31 | G750M | 1884 | $6248-6912$ | 0.56 | 0.051 | -137.62 | -0.25
STIS | 7403 | O57204040 | 1999 Jan 31 | G750M | 1890 | $6248-6912$ | 0.56 | 0.051 | -137.62 | 0
STIS | 7403 | O57204050 | 1999 Jan 31 | G750M | 1600 | $6248-6912$ | 0.56 | 0.051 | -137.62 | 0.25
STIS | 7403 | O57204060 | 1999 Jan 31 | G750M | 1884 | $6248-6912$ | 0.56 | 0.051 | -137.62 | 0.5
STIS | 7403 | O57204070 | 1999 Jan 31 | G750M | 1887 | $6248-6912$ | 0.56 | 0.051 | -137.62 | 0.75
STIS | 8497 | O5KP01040 | 2000 Feb 08 | G750L | 120 | $2900-5700$ | 4.92 | 0.051 | -150.34 | 0
STIS | 8479 | O5KP01020 | 2000 Feb 08 | G430L | 120 | $2900-5700$ | 2.73 | 0.051 | -150.34 | 0
WFC3 | 16246 | iebn12020 | 2020 Oct 28 | F502N | 1332 | $4972-5049$ | N/A | 0.039 | -20 | N/A
WFC3 | 16246 | iebn12010 | 2020 Oct 28 | F547M | 720 | $5075-5866$ | N/A | 0.039 | -20 | N/A
KOSMOS | GS01 | N/A | 2021 Dec 04 | Blue | 2700 | $4150-7050$ | 0.71 | 0.257 | 150 | 0
KOSMOS | GS01 | N/A | 2021 Dec 04 | Blue | 2700 | $4150-7050$ | 0.71 | 0.257 | 240 | 0
KOSMOS | GS01 | N/A | 2022 Jan 29 | Blue | 2700 | $4150-7050$ | 0.71 | 0.257 | 190 | 0
NIFS | N/A | GN-2018B-Q-109 | 2018 Dec 13 | Z | 1800 | $9400-11500$ | 1.03 | 0.043 | 0 | 0
NIFS | N/A | GN-2016A-Q-6 | 2016 Feb 28 | J | 2400 | $11500-13300$ | 0.88 | 0.043 | 0 | 0
NIFS | N/A | GN-2016A-Q-6 | 2016 Feb 28 | K | 2400 | $19900-24000$ | 2.09 | 0.043 | 0 | 0
Table 1: HST, KOSMOS, and NIFS observations of NGC 3227. The columns list (1)
instrument, (2) Program ID, (3) Observation ID, (4) observation date, (5)
grating (for spectra) or filter (for imaging), (6) exposure time for each
observation, (7) wavelength range (of the spectra) or bandpass (of the
filter), (8) spectral dispersion of the grating, (9) spatial scale of the
spectra, (10) position angle of the slits or angle of the images, using east-
of-north orientation, and (11) the spatial offsets of the slits or images from
the nucleus. The values for columns (8)-(9) for the HST data were obtained in
their corresponding instrument handbooks (Dressel, 2012; Riley, 2017).

NGC 3227 is a dynamic and fascinating Seyfert 1 galaxy from which, even after
decades of study, we can learn valuable information about AGN feedback and
outflow processes. There have been previous efforts by Fischer et al. (2013)
to constrain the orientation of the biconical geometry of the outflows by
measuring narrow and broad emission lines in the NLR of NGC 3227. Whereas
Fischer et al. (2013) relied primarily on optical data from the Hubble Space
Telescope (HST) Space Telescope Imaging Spectrograph (STIS) instrument, we add
multiphase and multiscale observations comprising optical, near-IR, and radio
data that exhibit kinematic details on both nuclear and galaxy-wide scales.
Additionally, we have made significant improvements to the methodology of
emission line fitting and the subsequent determination of the best geometric
model for the data. Those improvements and the resulting model are described
in this paper. Finally, the NGC 3227/3226 system has a significant history of
interaction. We are interested in examining whether or not a companion galaxy
affects a host galaxy’s feeding and feedback processes, and plan to address
this phenomenon in future papers.

##  2 Observations

###  2.1 Hubble Space Telescope (HST)

####  2.1.1 Space Telescope Imaging Spectrograph (STIS)

We used HST STIS archival observations to probe the kinematics of NGC 3227 on
small scales. The medium dispersion grating G750M has a spectral resolution of
1.8 Å (FWHM $\sim$ 83 km s-1 at 6500 Å) and a spatial resolution of
$\sim$0$\farcs$10 (2 pixels for Nyquist sampling). As shown in Figure 1, seven
parallel 52′′ $\times$ 0$\farcs$2 G750M slit observations, each separated by a
0$\farcs$05 gap and with position angle (PA) = -137.62°, were taken with
Hubble program ID 7403 (PI: A. Filippenko). The lower dispersion grating G430L
has a spectral resolution of 9.0 Å FWHM ($\sim$540 km s-1) and the same
spatial resolution as the G750M. A single slit observation at PA = -150.34°was
taken with Hubble program ID 8479 (PI: S.B. Kraemer), which included a G750L
spectrum at the same slit position as the G430L slit, but is not used in this
paper. The middle G750M slit (observation ID: O57204040) and the G430L slit
are centered over the AGN. A summary of the HST data is shown in Table 1. We
retrieved the calibrated data from the Mikulski Archive at the Space Telescope
Science Institute (MAST), and then used Interactive Data Language (IDL) to
extract the two-dimensional spectral images and convert to flux per cross-
dispersion (0$\farcs$05 $\times$ 0$\farcs$2) element.

####  2.1.2 Wide Field Camera 3 (WFC3)

We connected the locations of distinct NLR knots of emission to their measured
kinematics using [O III] images from WFC3 observations, which can be used to
trace the ionized gas outside the spatial range covered by the STIS slits. We
used a F547M image as the continuum to subtract from the line emission of the
F502N image. Both images were obtained from HST program ID 16246 (PI: M.
Revalski). This continuum subtraction first involved a conversion of data from
electrons per second to erg cm-2 s-1 for both images, which is done by
multiplying the data counts for each image by its filter’s inverse sensitivity
and its filter bandwidth. The resulting image exhibiting the ionized gas is
shown in Figure 1.

###  2.2 Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS)

Using the Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS) instrument
at APO, we obtained additional long-slit spectroscopy of NGC 3227 to map the
kinematics of the ionized gas on large (galactic) scales. The position angles
of these measurements were chosen to maximize coverage of the NLR as well as
the major and minor axes of the host galaxy. KOSMOS allows for three possible
slit locations that determine the desired wavelength range for a single grism.
For all KOSMOS measurements, we used the blue grism located at a “high” slit
location to provide data in the wavelength range of 4150 $-$ 7050 Å. This slit
position allowed for the measurement of both [O III] and H$\alpha$, which are
crucial in our analysis. Information on the observations can be found in Table
1.

We reduced the data to obtain calibrated spectral images using standard IRAF
routines including bias subtraction and flat-field correction (Tody, 1986,
1993). Standard stars selected from the Oke (1990) catalog were observed for
flux calibration, and arc lamp images taken at the telescope location of each
science exposure were used for wavelength calibration. Additional calibrations
were performed in IDL to correct the tilt of the spectrum in the cross-
dispersion direction (Gnilka et al., 2020) to produce calibrated 2D spectral
images.

###  2.3 Gemini North Near-Infrared Field Spectrograph (NIFS)

We utilized archival observations of NGC 3227 in the J- and K-bands from the
Near-Infrared Field Spectrograph (NIFS) at Gemini North. We also took new
Z-band observations with NIFS as shown in Table 1. These integral field unit
(IFU) observations obtained with adaptive optics have an angular resolution of
$\sim$0$\farcs$1 over a 3′′ $\times$ 3′′ field of view, which is important for
characterizing the outflows near the nucleus. Data reduction included image
trimming, flat fielding, sky subtraction, and wavelength calibration. We
followed the pipeline outlined in Merrell et al. (2020), which improves the
standard NIFS data reduction pipeline to account for necessary corrections
such as flux calibration and variance propagation to the final data cube. The
pipeline described in Merrell et al. (2020) was only written to reduce the
K-band, so we modified the code to include compatibility with the Z- and
J-bands. Reduced versions of the same J- and K-band observations were obtained
from Riffel et al. (2017) to verify consistency.

Each data cube covers 3′′ $\times$ 3′′, which equates to 345 pc $\times$ 345
pc assuming a distance of 23.7 Mpc (Tonry et al., 2001). The emission lines
that are observed in these spectra represent distinct gas phases.
Specifically, the H2 emission from the K-band maps the warm molecular gas;
Pa$\beta$ and He I are recombination lines in the J- and Z-band, respectively,
that trace a broad range of ionized gas; and [S III] emission from the Z-band
traces moderately-ionized gas similar to [O III] in the optical.

##  3 Methods

To understand the NLR kinematics of NGC 3227, we used the long-slit spectra to
isolate two groups of emission lines. The first group consists of H$\beta$
$\lambda$4861 and [O III] $\lambda\lambda$4959/5007, while the second consists
of H$\alpha$ $\lambda$6563 and [N II] $\lambda\lambda$6548/6583. Figure 2
shows these emission lines in a spectrum taken from the nuclear region.
Whereas KOSMOS can record emission lines from both groups in the same
observation, we have HST data utilizing the G430L and G750M slits to cover the
first and second group, respectively.

Figure 2: Examples of BEAT fitting (a) H$\beta$ $\lambda$4861 and [O III]
$\lambda\lambda$4959/5007 emission lines and (b) H$\alpha$ $\lambda$6563 and
[N II] $\lambda\lambda$6548/6583 emission lines using KOSMOS data. The blue
dashed line shows the systemic redshift of the H$\alpha$ and [O III]
$\lambda$5007 lines, respectively. We plot the spectra, systemic redshift, and
fits in the observed wavelength frame. The double-peaked feature at $\sim$6750
Å is the [S II] $\lambda$6716/6731 doublet, which will be incorporated into
future fits to obtain gas densities. In both figures, the black curve is the
composite fit, while the gray curve is the observed spectrum. The olive curve
is the broad component while the red, orange, and teal curves are the narrow
kinematic components. The green line marks the continuum level, which is a
linear fit to the averaged fluxes contained within the gray areas to the sides
of the emission lines.

###  3.1 Bayesian Evidence Analysis Tool (BEAT)

The 2D spectra allow us to characterize changes in emission lines as we look
away from the nucleus. We quantified these changes at each position along the
slit by fitting multi-component Gaussian profiles using the Bayesian Evidence
Analysis Tool (BEAT; Fischer et al., 2017) routine, which can separate
kinematic components. Physically, these components are tied to filaments and
knots like those seen in Figure 1. While the STIS slits can resolve individual
filaments, the wide area covered by the KOSMOS slit means that the resulting
spectrum at each point along the slit is a superposition of multiple knots’
motions. As a consequence, we expect and often find that areas closer to the
AGN, which tend to be more filamentary, will be fit with more components
(representing the individual knots) than areas that are farther from the
nucleus.

Figure 3: The result of BEAT fitting one (left), two (middle), and three
(right) narrow-line components to a spectrum. The broad line component (olive)
is present in all three fits. BEAT determined that for this spectrum, the two
component fit was optimal.

We applied BEAT to spectra from both long-slit spectroscopy (STIS and KOSMOS
data) and IFU data cubes (NIFS data), fitting each spectrum in the slit and
data cube, respectively. BEAT utilizes the MultiNest sampling algorithm (Feroz
& Hobson, 2008; Feroz et al., 2009, 2019; Buchner et al., 2014) to compute
Bayesian statistics and determine the fewest number of Gaussian components
that significantly improve the fit of the model to the data. For a set of
predetermined narrow emission-line species and a maximum number of allowed
Gaussian kinematic components, BEAT calculates the likelihood of a model.
Although emission line profiles are not always purely Gaussian (Heckman et
al., 1981; Veilleux, 1991), treating them as such for simplicity and
efficiency has been successfully employed for this type of study and has
allowed for accurate determination of velocity centroids and widths, as well
as fluxes of the emission-line components (Revalski et al., 2018, 2021;
Fischer et al., 2018; Gnilka et al., 2020). Gaussian model parameters were
fixed within a given range, including the intrinsic velocity widths,
acceptable wavelengths for line centroids, and the relative intensities of
certain lines such as [O III] $\lambda$5007/4959 and [N II] $\lambda$6583/6548
as 3.01 and 2.95, respectively (Osterbrock & Ferland, 2006). The lower ends of
the line widths were restricted by the instrument’s spectral resolution.
Although other kinematic studies of the NLR (Crenshaw & Kraemer, 2000; Fischer
et al., 2013, 2018; Meena et al., 2023) show outflows on scale of 1000-2000 km
s-1, we set the upper limit of the NLR to 1400 km s-1 (FWHM), which
sufficiently divides the NLR from the BLR in our fits. Consequently, when we
fit the BLR of these spectra, we utilized a lower limit of 1400 km s-1 (FWHM).
The lower limit for the flux levels of each component is 3$\sigma$ of the
continuum noise, and the upper limit is given by the peak flux of the
corresponding emission line data. We do not fit data that fail the criterion
of S/N $\geq$ 3.

BEAT also fits the continuum and allows for the specification of the
underlying broad-line emission, the process of which for NGC 3227 is described
in Section 3.2. It iterates through the parameter spaces, fitting Gaussians
and calculating their likelihoods, returning the likeliest model as the best
fit. For a given model, the likelihoods from all fits are summed to give a
Bayesian evidence value Z. The evidence value of each component describes the
overall likelihood of the number of components corresponding to the observed
spectrum. The logarithm of Z is taken, and shown in each panel of Figure 3.
The log(Z) value closest to 0 is representative of the most likely number of
components for the spectrum unless its improvement is insignificant relative
to the previous model fit. In other words, going from one number of components
to the next,

$\mathrm{ln}\left[\frac{Z_{i+1}}{Z_{i}}\right]\geq 5$ (1)

as per Feroz et al. (2011) where $Z_{i}$ and $Z_{i+1}$ are the evidence values
for two models fit with i and i+1 components, respectively. If Equation 1 is
true, then that constitutes “strong evidence” (99.3% probability) that the
more complex model is superior (Feroz et al., 2011). Figure 3 depicts an
example fit where the evidence values reveal that the two-component model is
the optimal choice for this spectrum.

Wavelength centroid, line width, and peak flux values of each component from
our best fits are used to create kinematic plots that show the radial
velocity, FWHM, and integrated flux profiles of the individual kinematic
components. These plots, described in greater detail in Section 4, are
integral to interpreting the gas kinematics.

###  3.2 Fitting Broad Lines

A defining characteristic of Seyfert 1 AGN like NGC 3227 is the presence of
broad emission lines in the nuclear region. Although the narrow components can
vary along the slits according to BEAT’s input parameters, the broad component
is unresolved in our observations and is treated as a point source, and thus
has fixed kinematics along the slits. As a result, the broad component
maintains a constant width and wavelength centroid along the slit, so the only
allowed variation is in the flux of the profile as it changes according to the
point spread function (PSF).

For each KOSMOS, STIS, and NIFS observation, we extracted a one-dimensional
spectrum from the nuclear region. Specifically, we used the spectrum with the
brightest continuum flux as our template for the broad components. We allowed
the routine to freely fit the broad emission with multiple Gaussian
components, with the stipulation that the line widths must be greater than
1400 km s-1 to avoid contamination from narrow line components. We ascribe no
significance to the individual broad components, and some may be due to other
emission lines such as Fe II in the H$\beta$ region. We performed these fits
separately for different epochs of observation because the broad lines in NGC
3227 are known to vary in both profile and flux (Bentz et al., 2023). The
resulting broad line components with fixed relative intensities are used as
templates in all subsequent fits for the H$\beta$ and H$\alpha$ regions.

###  3.3 Error Analysis

To use BEAT, we must input an uncertainty with each data point on every
spectrum we fit. For the NIFS data, after completing the pipeline outlined in
Merrell et al. (2020), we utilized the variance data cube and take the square
root of the variance for each point along each spectrum to approximate the
noise. For our KOSMOS and STIS data, we multiplied the standard deviation of
flux of the nuclear row by the square root of the flux at each point along the
spectrum divided by the average flux of the nuclear row. All three methods
were sufficient for producing noise arrays BEAT utilized in its fitting of all
the spectra.

For our STIS and KOSMOS spectra, the errors for the BEAT fits were calculated
by manually dividing the data in each slit into distinct kinematic groups
based on position and velocity. For each group, we calculated the median
absolute deviation and used that value as the velocity uncertainty for each
member in that group. In these instances, we calculated our own errors because
BEAT’s uncertainties were several times higher than expected for our resolved
spectra. We did not redo the uncertainties for the NIFS data because they are
reasonable values. However, in kinematic plots in this paper, we only display
velocity uncertainties for the STIS data because these are the only
uncertainties that we use in subsequent analyses in this paper.

##  4 Kinematics

Figure 4: H$\alpha$ kinematic plots for the KOSMOS slits along the major (top)
and minor (lower left) axes of the galaxy, and outflow axis of the NLR (lower
right). The top panel of each figure shows the radial velocity distribution of
H$\alpha$ emission, the middle panel shows the FWHM distribution of each
component, and the bottom panel shows the integrated flux distribution. The
kinematic components at each location are sorted according to decreasing
velocity in red (X), blue (circles), and green (squares). The black curve
running through all velocity plots is the rotation curve of NGC 3227 taken
from Schinnerer et al. (2000), projected along the slit position angles for
the host galaxy parameters given in Section 5.1.

###  4.1 APO KOSMOS Kinematics

The wide wavelength range of our KOSMOS measurements allow us to measure
H$\beta$ $\lambda$4861, [O III] $\lambda\lambda$4959/5007, H$\alpha$
$\lambda$6563 and [N II] $\lambda\lambda$6549/6585 simultaneously. However, in
our analysis of KOSMOS data we chose to focus on H$\alpha$ (and by extension,
[N II]) because of its brightness, ability to trace star formation and AGN
activity, and because it is less susceptible to extinction effects than the
bluer emission lines.

Figure 4 shows the ionized gas kinematics for H$\alpha$ in our three KOSMOS
slits. BEAT returned a maximum of three components for each fit, an upper
limit that was established based on observed kinematics in past studies
(Fischer et al., 2017; Meena et al., 2021, 2023; Revalski et al., 2021) and to
avoid excessive computational time. A consistent pattern in all three slits is
that we see the most components near the nucleus (over which the slits are
centered), and fewer components in the outer regions. The black curve present
in all velocity plots of Figure 4 originates from the rotation curve produced
in Schinnerer et al. (2000), which was derived from molecular 12CO data. The
maximum and minimum velocity values, and the extent to which the rotation
curve is stretched or squeezed in the spatial direction, vary according to the
projection of the rotation curve at each position angle. We can classify the
kinematics in the outer ($\geq$ 20′′, or 2.3 kpc) regions as predominantly
rotational motion, as evidenced by the flatness of the velocity profiles which
is consistent with the expected flatness of the rotation curve (Rubin & Ford,
1970). The fits in these regions primarily comprise a single component,
meaning that rotational motion around the galactic disk is the only observable
motion. This can be contrasted with the presence of two or three components in
the inner ($\leq$ 20′′) regions of all three slits.

To distinguish outflows from rotation, we have sorted the components in Figure
4 from high to low velocity. In Figure 4, we observe velocities and FWHMs
along the major axis of the galaxy consistent with an extension of the
rotation curve at projected distances of 15′′ (1.7 kpc) to 75′′ (8.6 kpc),
where the H$\alpha$ emission is primarily from H II regions. The flux plots in
Figures 4 and 4 also show hump-like shapes at distances of 55$-$65′′ and
$-$30′′ to $-$20′′, respectively. These correspond to the locations of the
spiral arms in NGC 3227.

The red points in Figures 4 and 4 generally trace the rotation curves, with a
few discrepancies at $-$4′′ to $-$2′′ in Figure 4 and $-$5′′ to 5′′ in Figure
4. At these locations, the radial velocities $|v_{r}|$ are practically 0 km
s-1, which are substantially lower than the velocities predicted by the
rotation curve in those regions of around 200 km s-1. Figure 4 shows minimal
agreement between the rotation curve and any of the kinematics, with the
observed $|v_{r}|$ measurements reaching 100$-$200 km s-1 despite expected
projections of rotational motion of around 10 km s-1. Overall, significant
excursions from the rotation curve in all three components indicate outflows
in the nuclear region of NGC 3227 that reach projected velocities up to 500 km
s-1.

###  4.2 HST STIS Kinematics

Figure 5 shows the ionized gas kinematics for the seven STIS G750M slits
tracing H$\alpha$ gas, as well as one G430L slit that traces [O III]. These
kinematic plots are in good agreement with those produced by Fischer et al.
(2013), where they performed a similar analysis on these data. Slight
differences arise because they did not use the BEAT fitting routine, but
instead used another Gaussian fitting routine wherein the number of components
is determined by eye. With the predetermined number of components, the program
then chose the model with the minimum chi-squared as the best fit. However, a
chi-squared parameter can be lowered by adding additional Gaussian components,
which can cause overfitting. Using the Bayesian likelihood to evaluate the
best model, as BEAT does, minimizes the chances of overfitting. In instances
where we fit the same number of components as them at a given distance along a
slit, the kinematics match. Nevertheless, we see variation in the kinematics
from them when we fit a different number of components at that location along
the slit, or if we fit components at more extended distances along the slit
than they could resolve with their routine.

Figure 5: The ionized gas kinematics of H$\alpha$ from the STIS G750M slits
and [O III] from the G430L slit. For slit position angles, refer to Table 1.
The top panel of each figure shows the radial velocity distribution of either
[O III] (G430L) or H$\alpha$ (G750M) emission. The red triangles and blue
squares represent the two kinematic components in order of decreasing
velocity, respectively. Errors in velocity were calculated by taking the mean
absolute deviation for distinct kinematic groups within each slit. The black
curve is the rotation curve of the disk given by Riffel et al. (2017). The
middle panel shows the FWHM distribution of each component, and the bottom
panel shows the integrated flux distribution.

Figure 5: Continued. Figure 6: The stellar velocity model for NGC 3227, taken
from Riffel et al. (2017). This LOS velocity field was created from NIFS
K-band observations of the stellar CO absorption bandheads. We utilize this
model in Section 4.3 to subtract the rotational motion from the observed
velocity fields. Figure 7: Ionized gas kinematic plots for the velocity
(left), FWHM (center), and flux (right) of the He I at $\lambda 1.083~{}\mu$m
emission from the NIFS Z-band. We incorporate the stellar kinematics model
from Riffel et al. (2017) to subtract out the rotational velocities. The X at
the center of each plot shows the position of the AGN. The top row shows the
plots for the first component of each fit, the middle row shows the plots for
the second component of each fit, and the bottom row shows the plots for the
third component of each fit. The components are sorted by speed from lowest
(top) to highest (bottom) at each position, with the bottom panel showcasing
the high-velocity outflows. Figure 8: Same as Figure 7 but for [S III]
$\lambda 9593$ Å emission from the NIFS Z-band. Figure 9: Same as Figure 7 but
for Pa$\beta$ $\lambda 1.2822~{}\mu$m emission from the NIFS J-band.

Figure 10: Same as Figure 7 but for H2 $\lambda 2.1218$ $\mu$m emission from
the NIFS K-band. In the leftmost plot, the velocity field is overlaid with the
contour of the H2 flux distribution shown in the rightmost plot. The dashed
line in the velocity plot represents the major axis of the galaxy.

Figure 1 shows how the STIS slits are generally oriented along the NLR axis,
although some of the more extended outflows visible $4^{\prime\prime}$ to the
north in the WFC3 image were not captured. The center of the G750M4 slit is
located directly at the Seyfert 1 nucleus. Additionally, the STIS slits are
close to the galaxy’s minor axis, which minimizes the projected radial
velocity due to rotation. The diminished impact of the rotational velocities
is shown by the projected rotation curves in each plot of Figure 5. For the
STIS slits, we used the rotation curve from Riffel et al. (2017) rather than
Schinnerer et al. (2000) because the former possesses a higher resolution
needed for the small-scale STIS observations, although we still projected the
rotation curve in the same manner described in Section 4.1. Assuming that
outflows and rotation are the primary components comprising the kinematics of
the circumnuclear region, we infer that we are primarily seeing outflows in
Figure 5 out to distances of 1$\farcs$3 (150 pc), with velocities reaching up
to 500 km s-1, similar to the largest amplitudes seen in the KOSMOS spectra.
Across all G750M slits, the outflows appear to extend out to about 1$\farcs$5
from the center of the slit, or about 170 pc. However, this distance increases
if we factor in the lateral distances from the slits, which are 0$\farcs$2
wide and separated by 0$\farcs$05, to the SMBH. When the slit locations are
properly considered, we see outflows of 500 km s-1 reaching 1$\farcs$7, or 200
pc, from the SMBH. Predominantly large FWHM values of the ionized gas out to
the same distances are consistent with outflows. Unsurprisingly, the much
higher spatial resolution of HST compared to APO allows us to better isolate
the high-contrast outflowing knots of emission in the nuclear regions. The few
points at larger distances ($\sim$3′′) in the STIS data are consistent with
rotation, although we don’t detect the outflow component seen in Figure 4 at
$\sim$5″, where there is spatial overlap between the KOSMOS and STIS data.
This is likely due to the much smaller areas sampled by STIS, which is
therefore unable to detect this component.

The [O III] emission shown in the G430L slit reveals redshifted outflows in
the of up to 500 km s-1 located 0$\farcs$2 SW of the nucleus. We also see
blueshifted outflows on the order of 300-400 km s-1 out to 0$\farcs$4 NE.

We also see velocity trends across several slits. For instance, many slit
positions show similarly blueshifted and redshifted velocities, indicating the
presence of a bicone that is funneling gas both towards and away from our line
of sight along the diametrically positioned cones that form the bicone
structure. Additionally, a curious feature across several slits is the
presence of blueshifted velocities peaking at $-$500 km s-1 that are
0$\farcs$5 – 0$\farcs$8 NE of the nucleus. We speculate on the source of this
outflow in the Section 6.

###  4.3 Gemini NIFS Kinematics

Kinematic maps, created from our reduced NIFS J-, K-, and Z-band data, display
the velocity, FWHM, and flux distribution for up to three components in
Figures 7–10. We have subtracted the rotational motion from the velocity maps
using the stellar velocity model for NGC 3227 given in Riffel et al. (2017)
and shown in Figure 6, so it can be assumed that mapped velocities are due to
non-rotational (i.e. outflowing) motions.

Our velocity maps therefore differ somewhat from those previously published
using these and other IFU observations of the nuclear region in NGC 3227
(Davies et al., 2006; Barbosa et al., 2009; Schönell et al., 2019; Bianchin et
al., 2022), which show the observed velocity fields containing the composite
rotational and outflowing motions, often using only single-component fits.

####  4.3.1 Z-band Kinematics

Figure 7 shows the three-component fits for the He I $\lambda 1.0830~{}\mu$m
emission in the Z-band. We fit both broad and narrow components, but will
focus on the latter in this analysis. The bottom panel shows the presence of
an extremely concentrated but high-velocity ($\sim$1000 km s-1) outflow in a
redshifted knot just SW of the nucleus. The middle panel shows a lower-
amplitude and more extended pattern of outflow that is primarily blueshifted
to the NE and redshifted to the SW. The upper panel shows an extended
component that can be attributed to rotation (after subtraction of the
rotation model), except for perhaps a mildly redshifted component to the SW
once again.

Figure 8 shows the two-component fits for the [S III] $\lambda 9533$ emission
in the Z-band. The components are sorted in order of decreasing velocity: the
bottom panel highlights the high-velocity outflows and the top panel exhibits
the lower-velocity outflow structure. Along the top panels, we see redshifted
outflows on the order of 100 – 150 km s-1 extending southwards over a distance
of almost 1′′ from the nucleus, with some areas reaching speeds of almost 200
km s-1. We also see a blueshifted outflow extending towards the NE direction
from the nucleus, with speeds of $-$150 to $-$100 km s-1 out to an orthogonal
distance of 0$\farcs$75\. The FWHM plot for this map does not have many
discernible features, although the values are notably smaller on the west end
than the east end by about 200 km s-1. The flux distribution is relatively
smooth compared to the HST [O III] image, because the Gemini NIFS PSF has much
broader wings than that of HST and its cameras.

Figure 11: A demonstration of how the bicone model changes based on whether
one chooses the range of bicone opening angles to be small (7°, left) or large
(39°, right). All other bicone parameters are the same. The gray areas
represent the model velocity space, and the blue points are data from the
corresponding STIS slit that we aim to match with the models.

The lower set of panels in Figure 8 shows high-velocity outflows in the inner
0$\farcs$25 region around the nucleus, with speeds reaching up to 900 km s-1.
The chaotic motion often associated with outflows is also reflected in the
corresponding FWHM plot, which shows line widths as large as 800 km s-1.

####  4.3.2 J-band Kinematics

Figure 9 shows the emission of Pa$\beta$ $\lambda 1.2822~{}\mu$m seen in the
J-band. Unlike the lines observed in the Z-band, only a single component was
needed to sufficiently fit Pa$\beta$. The velocity plot shows clearly defined
blueshifted and redshifted lobes with their centers $\sim$0$\farcs$3 from the
nucleus in the NE and SW directions, respectively. Stretching outwards from
the west side of the blueshifted lobe is another region of blueshifted
outflow, albeit with a much lower $|v_{r}|$ of only $\sim$80 km s-1. We do not
see a similar trend in the redshifted lobe. We see a correspondence between
the velocity and FWHM plots, as the regions with high $|v_{r}|$ show elevated
line widths reaching 850 km s-1. Curiously, we see very low line widths in the
region with the secondary blueshifted outflow. The flux profile in Figure 9
shows a clear radial decrease in flux from the brightest point in the center,
which corresponds to the SMBH.

Overall, the emission lines from ionized gas in the NIFS observations show
high-amplitude blueshifted velocities in the NE and high-amplitude redshifted
velocities in the SW, reaching maximum values of 400 – 800 km s-1 at distances
0.2′′ – 0.4′′ from the SMBH. Lower amplitude blueshifts and redshifts that
cannot be attributed to rotation can be seen on either side of the nucleus
over the NIFS field of view. This pattern is very similar to that seen in the
HST STIS observations.

####  4.3.3 K-band Kinematics

Figure 10 shows the emission of H2 $\lambda 2.1218$ $\mu$m seen in the K-band.
We see interesting structure in all three of the kinematic plots from our
single-component fit, also seen but not as pronounced in the observed velocity
fields by Schönell et al. (2019) and Bianchin et al. (2022), likely due to
differences in fitting methods. The rotation-subtracted velocity map in Figure
10 shows two adjacent redshifted and blueshifted lobes on the NW and NE sides
of the nucleus, respectively. The red lobe expands northwards out to
$1^{\prime\prime}$, while the blue lobe is more concentrated and has a width
of $\sim$0$\farcs$4\. The speeds that we see in the H2 maps are much lower
than those in the other NIFS velocity maps, with maximum values of
$|v_{r}|\approx 70$ km s-1, indicating that the H2 kinematics are rotation-
dominated. The dashed line marking the major axis of the host disk reveals the
symmetry of the blueshifted and redshifted emission along it. The lower right
corner shows an area that appears to also have redshifted emission, but due to
the low FWHM and flux values, those values could be due to noise in the
observed spectra. The FWHM plot in Figure 10 reveals an unusual curved
structure that coincides with regions of the redshifted emission.

In Figure 10, we see a rather unique bean-like shape about $1^{\prime\prime}$
long and centered over the SMBH. We also overlay the contours of the flux map
onto Figure 10 and observe that the redshifted emission corresponds to a
region 2$-$3 times fainter than the peak emission. However, we also see that
the blueshifted emission is cospatial with the flux contours on the northern
end.

##  5 Bicone Model

Fischer et al. (2013) describe the structure of a biconical outflow model for
NGC 3227’s NLR. They utilized the kinematic modeling code from Das et al.
(2005) to simulate models dependent on input parameters including the bicone’s
orientation on the sky, inclination with respect to our line of sight (LOS),
minimum and maximum half-opening angle (HOA), turnover radius, and height. The
model also follows a velocity profile which starts at 0 km s-1 in the center
and increases linearly until a specified turnover radius, after which the
velocity decreases linearly until zero at a predetermined maximum height along
the bicone axis. This empirical velocity law appears to match the velocity
trend for many Seyfert NLRs quite well (Fischer et al., 2013).

For a given set of input parameters, the model produces a plot that shows the
range in possible velocities as a function of distance from the AGN. Figure 11
shows the ways in which these plots can vary by changing the range in HOA, but
it also exemplifies a characteristic bowtie-like shape whose peaks reflect the
chosen turnover radius. For each STIS slit, Fischer et al. (2013) compared the
measured [O III] velocities to the velocity range given by the model and
adjusted the input parameters accordingly to find the best match. In the
absence of a practical statistical algorithm, the best match between the model
and data was determined by eye. However, Figure D.7 of Fischer et al. (2013)
shows large discrepancies between the model and data for NGC 3227. This paper
defines a new biconical outflow model that provides a better match for the
data.

###  5.1 Development of a New Model

Our goal is to determine a bicone model that most concisely fits the data. We
used the same code utilized in Fischer et al. (2013) and improved the
selection of the model that best fits the data.

In order to determine the optimal model, we used the bicone parameters given
by Fischer et al. (2013) as priors and generated over 300,000 bicone models
with corresponding velocity plots like those shown in Figure 11. One condition
we implemented was that the bicone inclination angle from the LOS must have a
smaller value than the inner opening angle, because the Seyfert 1 designation
for NGC 3227 requires visibility of the central engine. We iterated through
five variable parameters (bicone inclination, inner opening angle, outer
opening angle, turnover radius, and bicone PA), creating a model for every
combination of parameters within $\pm$10°of prior estimates for each STIS slit
position, using step sizes of 1°. Two parameters that we did not vary are the
maximum height and maximum velocity, which we kept constant at 150 pc and 600
km s-1, respectively. We chose these values based on the kinematics of our
data, and although these values are slightly different than those reported in
Fischer et al. (2013), the difference is negligable.

Each model shows the projected bicone kinematics at each of our STIS slit
positions. We refer to the “model velocity space” as the gray regions in
Figure 11. For each slit, the algorithm determines the “velocity fraction,”
which is the fraction of data points that fall within the model velocity space
and characterizes how well the model fits the data. However, our data
represent a mix of rotating and outflowing motions, and because we want to use
outflows to determine the orientation of the NLR bicone, we removed data
exhibiting characteristics of rotational motion. Riffel et al. (2017) defined
a rotation curve for the inner 2′′ of NGC 3227, and in the absence of
uncertainties from that model, we assume that data that fall within $\pm$20 km
s-1 of the rotation curve and outside the model velocity space are rotational.
We subtract the number of rotational data points from the total number of
points that we fit with the model to ensure that we are only fitting
outflowing data to the bicone model.

Parameters | Fischer et al. | This Work
---|---|---
Galaxy PA |  $-31$° |  $-31$°
Galaxy Inclination | 63°(SW closer) | 48°(SW closer)
Bicone PA | 30° | 27 ${}^{+4}_{-2}$ °
Bicone Inclination | 15°† (SW) | 40${}^{+5}_{-4}$°(SW)
Inner HOA | 40° | 47${}^{+6}_{-2}$°
Outer HOA | 55° | 68${}^{+1}_{-1}$°
Turnover radius | 100 pc | 26${}^{+6}_{-6}$ pc
Max height | 200 pc | 150 pc
Max velocity | 500 km s-1 | 600 km s-1
Table 2: Rows are (1) major axis of galaxy from Schmitt & Kinney (2000), (2)
inclination of galaxy from Xilouris & Papadakis (2002), (3) major axis of
bicone axis, (4) inclination of bicone axis relative to plane of sky, (5)
minimum HOA relative to the LOS, (6) maximum half opening angle, (7) turnover
radius, (8) maximum height of bicone along its axis, and (9) maximum outflow
velocity, located at turnover radius. Errors for this work are reported as a
68% confidence interval.
† Fischer et al. (2013) lists inclination from the plane of the sky, whereas
we opt to use the angle from our LOS. Their value has been converted to our
frame of reference for consistency.

The parameters that most drastically impact the geometry are bicone
inclination, the inner and outer half-opening angles of the bicone, the
turnover radius, and the bicone position angle. The opening angles had to be
considered carefully because they can easily lead to model overfitting. Figure
11 shows the effect that a small and large range of opening angles can have on
the resulting bicone model. A bicone with a wide range in the opening and
closing angles will always envelop a larger fraction of the data than a bicone
with a narrower angular range. Simply determining the model with the highest
velocity fraction is insufficient to finding the optimal bicone model. Thus,
we must apply a normalizing weight based on the size of the model velocity
area to act as a counterbalance. For each slit position, we compiled all 2D
model velocity areas into histograms, which revealed normal distributions. We
use those distributions to weight each model velocity area, and divide the
velocity fraction by the weighted model velocity area to determine the density
of fitted points per unit model velocity space, which we call the “weighted
velocity fraction.”

Figure 12: Projection of our new bicone model, outlined in white, overlaid on
the WFC3 [O III] image, shown by the contours. The gray disk represents the
plane of the galactic disk, which intersects with the [O III] line emission.
The unobscured part of the near cone is shaded in blue, while the unobscured
part of the far cone is shaded in red. In this orientation, the [O III]
emission is entirely in front of the bicone and is blueshifted.

We average the weighted velocity fractions for all seven STIS slits
corresponding to a given set of input parameters and deemed the set of
parameters with the highest average to be the optimal model, for it maximizes
the number of fit data points per unit area. Those parameters are given in
Table 2, with uncertainties marking parameter values that reside within the
68% confidence interval for the average velocity fractions.

Table 2 shows that there are significant changes in the new bicone model
compared to that described in Fischer et al. (2013). Figure 12 shows the
projection of the bicone on to the same WFC3 image of [O III] emission as
Figure 1. Most notable from Fischer et al. (2013) is the change in
inclination, which steepened significantly from 15°to 40°. This value is in
much better agreement with the measurement of $33.2^{+13.5}_{-9.1}$°from Bentz
et al. (2023), based on modeling of the broad-line region (BLR), and suggests
that the confinement structures for the BLR (accretion disk) and NLR (torus)
are co-aligned. Another difference is in the turnover radius, which describes
the spot where deceleration overtakes acceleration and is shown in projection
as the locations of the maximum absolute velocities in Figure 13. Whereas
Fischer et al. (2013) found the turnover radius to be 100 pc, we determine it
to be 26${}^{+6}_{-6}$ pc. Additionally, we find an outer HOA of
68${}^{+1}_{-1}$°, which also aligns with the value of
64.7${}^{+18.3}_{-11.8}$°determined in Bentz et al. (2023).

Figure 13: Each figure shows the kinematic profile of a STIS slit. The blue
points show the observed [O III] $\lambda$5007 velocities. The gray regions
show the model velocity areas, and represent the range of acceptable
velocities for the updated version of the bicone model. We define the area of
stellar rotation, which is encompassed by the black outline, as points which
fall within $\pm$ 20 km s-1 of the rotation curve given by Riffel et al.
(2017).

###  5.2 Comparison of Data to Model

Figure 13 shows how the range of projected velocities from the model compares
to the velocities from the STIS data. We can divide the plot into four
quadrants. In the figure, the negative direction refers to the SW. The top
half represents emission from the further redshifted cone, while the bottom
half shows emission from the nearer blueshifted cone. The disk of the galaxy
intersects with the AGN in such a way that positive distances show emission
primarily from the part of the bicone in front of the disk, while negative
distances show emission from the part of the bicone behind the disk. There is
not much emission from the SW in any of the slits due to the prominent dust
lanes from the disk that block our view (see Figure 14), except within the
inner $\sim$0$\farcs$8 where the [O III] emission is bright enough to be seen
through the extinction.

The overlap between the model and data in this work is substantially improved
from that in Fischer et al. (2013), and we see generally decent agreement
between data and model in all of the slits. In a number of slits, we see many
points that follow the rotation curve, indicating strong rotational motions in
the inner 1′′, which is already known (Riffel et al., 2017; Bianchin et al.,
2022). This rotation is also seen in the data in slits G750M2, G750M3, and
G750M4 in the regions beyond 2′′, as shown in Figure 5.

There are two main discrepancies between the models and observed velocities.
First, the outside slits (G750M1, G750M2, G750M6, G750M7) show observed
velocities in the inner regions that don’t quite match either rotation or
outflows, particularly on the NE side. These may be due to disturbed
kinematics (Fischer et al., 2018), where outflows are running into the dust
lanes, consistent with the large FWHM values for most of these points (Fischer
et al., 2019). Second, there is the large clump of blueshifted velocities
peaking at $-$500 km s-1 that is 0$\farcs$5 – 0$\farcs$8 NE of the nucleus in
most of the slits, which was previously mentioned in Section 4.2. In Figure
13, we see that a number of those points lie outside the model. We discuss
this discrepancy in Section 6.

##  6 Results and Discussion

###  6.1 Connection to NGC 3227’s Circumnuclear Ring

Using observations of CO and HCN with the IRAM Plateau de Bure interferometer
(PdBI) at 0$\farcs$6 resolution, Schinnerer et al. (2000) found a 3′′ (345 pc)
diameter molecular ring of gas centered near the SMBH with much stronger
emission on its eastern side. The ring is at PA = 160° and inclination = 56°,
in agreement (to within $\sim$10°) with the large-scale H I 21 cm (Mundell et
al., 1995), large-scale stellar (Fischer et al., 2017), and nuclear stellar
(Riffel et al., 2017) disks. Between 1′′ and 3′′, the ring rotates in the same
way as the large-scale gas and stars, but the emission appears to show either
counterrotation or noncircular motions inside of 1′′. Schinnerer et al. (2000)
found that the kinematics of the molecular gas couldn’t be replicated by a bar
in the inner 1′′ of NGC 3227, but instead proposed a molecular ring that
starts 75 pc from the nucleus and bends to be perpendicular to the host galaxy
plane at a distance of 30 pc. The nuclear kinematics in both cold and warm
molecular gas have been a topic of study for over a decade (Alonso-Herrero et
al., 2019; Davies et al., 2014; Hicks & Malkan, 2008; Schönell et al., 2019).

Alonso-Herrero et al. (2019) present ALMA CO observations of the nuclear
molecular ring at 0$\farcs$1 – 0$\farcs$2 resolution and confirm strong
noncircular motions at distances $\leq$ 1′′ from the nucleus, primarily along
the disk’s kinematic minor axis. They find that the noncircular motions can
best be explained by outflow from the inner part of the ring that lies along
the PA and inclination of the host disk, with the far side of the ring in the
NE direction. They get a slightly better fit by including a warp with the far
side of the inner ring instead in the SW direction, as suggested by Schinnerer
et al. (2000). However, this would imply inflow at deprojected velocities of
at least 150 km s-1 assuming their interpretation of disk which is
substantially higher than the inflow velocities expected of lower luminosity
AGN, which is on the order of $20-50$ km s-1 (Davies et al., 2006). They also
demonstrate that infrared IFU observations of H2 from Davies et al. (2014)
show a similar velocity field for the warm molecular gas.

Our NIFS H2 radial velocity, dispersion, and flux maps shown in Figure 10 are
similar to those from other studies (Riffel et al., 2017; Alonso-Herrero et
al., 2019; Davies et al., 2014; Hicks & Malkan, 2008; Bianchin et al., 2022).
However, the rotation-subtracted velocity map shows the axis of the presumed
H2 outflow slightly offset from the nucleus and at a PA $\approx$ 90°,
compared to the cold ring’s minor axis at 50°– 70°(Schinnerer et al., 2000;
Alonso-Herrero et al., 2019). Moreover, redshifted emission at $\sim$60 km s-1
is visible almost 1′′ from the nucleus, while the blueshifted outflows are
much more concentrated. Due to the high deprojected velocities in both the
warm and cold molecular gas (up to 150 km s-1) and their similar orientations
with respect to the large-scale disk, we prefer the interpretation of
redshifted emission in the east and blueshifted emission in the west as
molecular outflow.

With this interpretation, the geometry of our biconical outflow model and
galactic disk as shown in Figure 12 provides a natural explanation for the
observed kinematics of both ionized gas and cold/warm molecular gas. For the
ionized gas, the NE side of the near bicone is unobscured, has high projected
blueshifts, and therefore dominates the [O III] images and optical spectra.
The unobscured portion of the redshifted NE side of the far cone also
contributes significantly, especially to the more extended emission. The
molecular outflows originate in the intersection between the bicone and host
galaxy disk and move along the disk. The longer-wavelength observations
experience smaller or no extinction compared to the optical, so that we see
redshifts in the east and blueshifts in the west. Our observations do not rule
out a warp in the disk inside of $\sim$30 pc, and in fact there is likely to
be an interior warp to provide a torus-like structure (at PA $\approx$ $-$63°,
inclination $\approx$ 27°, NE side closer) that produces the observed bicone.

Figure 14: Color-composite image of the inner region surrounding NGC 3227’s
AGN where red colors are from the HST WFC F658N filter, green colors are from
the HST WFC3/UVIS F547M filter, and blue colors show F550M and F330W filters
from Hubble’s Advanced Camera for Surveys High Resolution Channel (HRC). The
black star shows the location of the nucleus. Image credit: Judy Schmidt.

###  6.2 Kinematic Properties of the Ionized Gas

Fischer et al. (2018) categorizes the observed motions of the ionized gas in
the NLR into three groups:

  1. 1.

Motion indicative of outflowing material. These data points are typically
characterized by a high velocity ($\geq$ 400 km s-1) and FWHM ($\geq$ 300 km
s-1), and are representative of a source of acceleration needed to account for
velocities too large for gravitational acceleration alone.

  2. 2.

Motion caused by the rotation of the galactic disk. These points are typically
characterized by a low velocity ($\leq$ 400 km s-1) and FWHM ($\leq$ 300 km
s-1), and show a symmetric pattern of blueshift/redshift on either side of the
nucleus.

  3. 3.

Motion affected by a kinematic “disturbance.” This is gas affected by an
impact or turbulence that could cause a redistribution of the direction of
motion. The disturbed gas shows low velocities ($\leq$ 400 km s-1) and high
FWHM ($\geq$ 300 km s-1), as the gas is being accelerated but its motion is
impeded to some extent by its surroundings.

Separating the observed kinematics into these three groups can be challenging.
For example, rotational motion and outflowing motion can have similar
kinematic signatures if the outflow is in the same direction as the rotation.
Another possibility is that a measurement of low velocity may actually be
high-speed outflowing material whose motion is primarily across our line of
sight. Nevertheless, by comparing the observed large-scale velocities to the
rotation curves from the stars or cold gas as discussed in Section 4, we can
separate these motions with a good deal of confidence.

####  6.2.1 Extents of the Outflows and Disturbed Gas

In Figure 4, H$\alpha$ emission shows consistently sustained outflows of up to
$-500$ km s-1 out to $5^{\prime\prime}$ ($\sim$600 pc) in the faintest of
three components. This extent is significantly greater than the height of the
bicone model ($\sim$200 pc), which we determined based on the STIS data.
However, the bicone height does not act as an upper limit to the extent of the
outflows, but rather correlates with the turnover radius. Nevertheless, these
high velocity points are still within the bicone and consistent with radiative
driving from the innermost parsecs, as shown in Section 7. Additionally, in
Figure 4, the velocities from 3$-$7′′ SE are practically 0 km s-1, which are
substantially lower than the velocities predicted by the rotation curve in
that region of around 200 km s-1. This is likely due to averaging of two
components (redshifted rotation, blueshifted outflow) that could not be
separated due to their large FWHM. At distances $<|15|^{\prime\prime}$ (1.7
kpc), there is a clear rotational component (primarily brighter points)
extending to the nucleus, although most of this component appears to be
“disturbed” with large FWHM. Points at larger distances (up to 75′′ or 8.6
kpc) are clearly due to pure rotation.

The projection of rotational kinematics is minimized along the minor axis, so
the observed motions in Figure 4 must be primarily due to outflows, albeit at
projected velocities $\leq$ 250 km s-1. Thus, it is puzzling to see $\sim$100
km s-1 emission at $20-30^{\prime\prime}$ SW, especially in the blueshifted
direction when we expect any rotational motion to be redshifted. The
kinematics along the outflow axis (Figure 4) show evidence for pure rotation
at large distances ($\sim$55′′), disturbed rotation in the higher velocity
component from $-$10′′ to $\sim$10′′, and outflows in the lower velocity
component out to $\sim$7′′ ($\sim$800 pc).

Overall, our results indicate that the ionized outflows in NGC 3227 extend to
distances of about 800 pc from the central engine. However, the majority of
the ionized gas is kinematically disturbed out to $\sim$15′′ (1.7 kpc), a
large fraction of the bulge size, which would make it difficult to form stars
from this gas.

A curious feature across several slits in Figure 5 is the presence of
blueshifted velocities peaking at $-$600 km s-1 and positioned 0$\farcs$5 –
1$\farcs$2 NE. In the slits G750M2, G750M3, G640M4, G750M5, G750M6, and
G750M7, $|v_{r}|$ increases with distance, which is a clear sign of outflowing
motion as described by the radiative driving formulism (see Section 7).
However, Figure 13 shows that a number of data associated with those outflows
fall outside the model. Gas clouds that have been accelerated to high speeds
at significant distances from the SMBH were likely launched from within the
innermost few pc of the SMBH. In these cases, the gas is likely decelerating
at those distances, implying that they had reached a peak velocity at closer
distances. One input parameter to create the bicone models is the maximum
projected velocity, $v\mathrm{{}_{max}}$. We limited the value of
$v\mathrm{{}_{max}}$ to 600 km s-1 so that there wouldn’t be an inordinate
amount of empty velocity model space that would come with generating models
that had higher $v\mathrm{{}_{max}}$ values and which fit those discrepant
points, but a bicone model that successfully fit those data could surely be
generated.

Additionally, following the logic of rotational kinematics close to the minor
axis given the orientation of the galactic disk, we expect to see small ($\sim
50$ km s-1) levels of redshifted rotational motion in the SW direction, as
indicated by the green rotation curve plotted in Figure 5. It is thus
surprising to note the presence of blueshifted rotational motion in the SW
regions of the G750M5, G750M6 and G750M7 plots. These kinematics are denoted
by the blue data from $-$1$\farcs$2 $-$ 0′′, which we attribute to rotation
due to the relatively constant velocities across distance. One possible
explanation for this discrepancy is that the circumnuclear molecular ring
described in Section 6.1, which is creating counterrotation in the inner 1′′,
may be affecting the motions of the ionized gas so that they are blueshifted.

####  6.2.2 High-velocity Outflows and Asymmetries

We see high-velocity outflows in the He I and [S III] emission, both of which
are measured in the Z-band. In both cases, the outflows reach a velocity of
$\sim$900 km s-1 but stay fairly close to the SMBH, reaching distances of only
$\sim 0\farcs 1$ (11 pc). Figures 7 and 8 show the spatial coverage of these
outflows. Barbosa et al. (2009) also find evidence of high-velocity [S III]
outflows, but whereas we see them only in the redshifted direction, they find
speeds of 900 km s-1 in the blueshifted direction to the NW of the nucleus.
They also find redshifted outflows in the area just south of the nucleus,
reaching velocities of up to 500 km s-1. High-velocity outflows outside of the
general flow pattern of ionized clouds are often seen close to the nucleus in
the NLRs of nearby AGN, reaching a radial velocity of up to $\sim$2000 km s-1
(Das et al., 2005), which provides an effective limit for our fits.

Another noticeable feature among the velocity maps for [S III] (shown in
Figure 8) is an asymmetry in the velocities, in the sense that the blueshifted
and redshifted regions are not diametrically opposed with respect to the
nucleus. We expect symmetry from gas whose motions are entirely rotational, so
deviations are likely attributable to the outflows that are present in the
inner arcsecond. Asymmetrical outflows have been mentioned in previous studies
of these NIFS observations (Riffel et al., 2017, 2021; Schönell et al., 2019;
Bianchin et al., 2022), as well as those based on other ground-based
observations of NGC 3227 (Hicks & Malkan, 2008). The [S III] emission reflects
the shape of the bicone in the NE quadrant (see Figure 1). The SW cone is
revealed in these observations due to less extinction in the infrared by the
host galaxy’s disk, although extinction by dust lanes SW of the nucleus (see
Figure 14) may still be responsible for its asymmetric location. The second,
fainter kinematic component in the SW is slightly blueshifted, consistent with
STIS data, although it’s not clear why we do not detect a faint redshifted
component in the NE. Barbosa et al. (2009) note two clumpy blueshifted [S III]
regions, located 2$\farcs$4 and 0$\farcs$7 from the nucleus in the NE
direction. They propose that these regions are caused by compression from a
radio jet onto the interstellar medium (ISM), which is supported by the
orientation of the radio contours from 3.6cm data from the Very Large Array
(Nagar et al., 1999; Schmitt et al., 2001). Due to the smaller field of view,
our NIFS data show only the clump at $\sim 0\farcs 5$.

For Pa$\beta$, shown in Figure 9, the outflows peak in velocity at 0$\farcs$3
to 0$\farcs$5 on either side of the nucleus, similar to that seen in the STIS
data. Schönell et al. (2019) also finds a high concentration of blueshifted
gas at this location in the NW direction, and Bianchin et al. (2022) see this
gas in their map of the second kinematic component of Pa$\beta$. Overall, the
velocity patterns, velocity dispersions, and fluxes of the ionized gas in the
nuclear regions of NGC 3227 match those in other studies.

Figure 15: Left: Flux contour plots using multiwavelength data including
CO(2-1) (Alonso-Herrero et al., 2019), [O III] from the reduced HST WFC3
image, and He I and H2 from the NIFS Z- and K-bands, respectively. To create
the flux contours for He I, we decided to sort the three components in order
of flux. Because the latter two components are significantly dimmer than the
first, we opted to only show the contours for the first component. The
background color map shows the flux density of CO(2-1). Right: Velocity plots
showing the contour of He I, H2, and [S III] outflows overlaid on to CO(2-1)
velocity map from Alonso-Herrero et al. (2019). For the He I velocity
contours, we chose to sort the components by velocity, as is shown in Figure
7, and we plot all three components. The dashed contours show negative
(blueshifted) velocities, while solid contours show positive (redshifted)
velocities. It is important to note that although velocity due to stellar
rotation has been subtracted from He I, H2, and [S III], it has not been
subtracted from the CO(2-1) emission. In both plots, the X at the center shows
the location of the nucleus.

###  6.3 Multiphase Correlation

We can characterize the kinematics to better understand how the various phases
of gas that being studied – ionized, warm molecular, and cold molecular –
interact with each other. Fischer et al. (2017) noted in their study of Mrk
573 that there is a progression of increasing distance and velocity from dust
lanes, to H2 emission, and finally to [S III] emission, indicating in situ
acceleration, heating, and ionization of the cold gas as the primary source of
NLR outflows. A similar trend is found in Mrk 3 (Gnilka et al., 2020).

Figure 15 shows how the flux contours of CO(2-1), [O III], H2, and He I
significantly overlap with one another in the innermost couple of arcseconds
in NGC 3227. Going NE from the nucleus along the near cone, the above trend
appears to hold as the extents and velocities of the gas increase with
increasing ionization level. The only exception is the extent of the He I
recombination line, although its velocity follows the trend.

However, the opposite trend in level of ionization is seen along the bridge of
gas about 1′′ in extent, running SE to NW across the nucleus and capped by
knots of CO(2-1) emission. We see a phase progression as we move in either
direction along the bridge, starting with hot [O III] and warm He I emission
in the center, moving outwards to cooler H2 gas, which has its densest clumps
$\pm$0$\farcs$25 (29 pc) from the center, and finally reaching the cool
CO(2-1) clumps at $\pm$0$\farcs$5\. This progression indicates the hollowing
out of the cold gas reservoir at the nucleus by ionizing radiation as
suggested by Alonso-Herrero et al. (2019), which then flows along the cones.
Thus, the general trend of in situ heating, ionization, and acceleration of
cold molecular gas to form the NLR outflows continues in NGC 3227, although at
present most of the action appears to happen within $\sim$0$\farcs$5 (58 pc)
of the nucleus.

We also study the velocities of the various phases to understand their
interplay with one another. Figure 10 shows how the velocities of CO(2-1), H2,
He I, and [S III] are correlated with one another. We notice several instances
of overlap between positive and negative contours representing redshifted and
blueshifted emission, respectively. We assume that based on the bicone
structure observed in Figure 12, in these instances, we are observing emission
from both cones in the bicone structure. As a result, we will analyze the
blueshifted and redshifted kinematics separately.

We see blueshifted outflows at 0$\farcs$4 NE in [S III], which contain slight
overlap with the edge of the He I outflows. We see a progression in velocity
as the He I outflow reaches 300 km s-1 on its northern end 0$\farcs$2 NE,
after which it transitions to [S III] emission that spans an additional
0$\farcs$4 NE at velocities of $\sim$100 km s-1, until it finally leads into
the surrounding CO(2-1) emission, which is moving at speeds of $\sim$70 km
s-1. One thing to note is that although we do see a velocity progression in
the blueshifted emission, we do not see a corresponding phase progression.

The redshifted emission appears predominantly to the SW of the SMBH. The
exception to this is the H2 emission, which we are not heavily considering in
the following commentary about outflows because we have established that its
kinematics are primarily rotational (see Section 4.3.3). Much like the
blueshifted outflows, the redshifted outflows follow the same spatial
progression of transitioning from He I to [S III] to CO(2-1). The He I
outflows, located entirely within the hollowed CO(2-1) cavern, reach
extraordinary speeds of 800 km s-1 and extend SW towards the [S III] outflows,
which have speeds of 100$-$150 km s-1. It then disperses into the CO(2-1)
emission, which has speeds of 75$-$125 km s-1.

By comparing the kinematics of the CO(2-1), H2, He I, and [S III] to one
another, we see how the outflowing gas changes in phase and speed as the gas
is accelerated away from the SMBH. In both the redshifted and blueshifted
directions, the He I gas moves at high (250$-$800 km s-1) speeds from the
nucleus, until it interacts with slower (100$-$150 km s-1) [S III] gas
0$\farcs$2-0$\farcs$25 from the nucleus. Ultimately, the gas reaches the
CO(2-1) emission, which is moving even slower (70$-$125 km s-1). Thus,
observing all these measurements together, we can observe how velocity tends
to decrease with distance from the center.

###  6.4 Influences from NGC 3226?

Tidal influences on the AGN have been observed in other studies. Fischer et
al. (2017) found that narrowband [O III] imaging of Mrk 573 shows the presence
of a 3′′ filament in the vicinity of the nucleus. They interpret the filament
as a minor merger potentially undergoing tidal stripping as it infalls towards
the AGN. Similarly, Gnilka et al. (2020) found that a large-scale gas/dust
disk at the center of Mrk 3 is oriented towards a companion galaxy, which
provides evidence for tidal fuelling of Mrk 3’s AGN by that companion galaxy.

Seminal works from Rubin & Ford (1968) and Mundell et al. (1995) have studied
the tidal connections between NGC 3226 and NGC 3227 that have led to a richly
intertwined dynamical history for the two galaxies. Appleton et al. (2014)
note the complex structure of H I and optical gas in this system comprising
NGC 3226 and NGC 3227, also known as the Arp 94 system, and suggest that NGC
3226 may itself be the result of a recent merger, and may be sharing tidal
debris from that event with NGC 3227. Nevertheless, in our KOSMOS measurements
shown in Figure 4, which span almost the entire length of Arp 94, we see no
sign of unusual kinematic signatures that would suggest a noteworthy tidal
influence on the H$\alpha$ gas. We hypothesize that at distances close to the
nucleus, any distinct kinematic signatures from the infalling gas are no
longer distinguishable because integration into the disk of NGC 3227 has
likely smoothed them out.

##  7 Radiative Driving

In the NLR, photoionized gas is likely pushed away from the nucleus as a
result of radiative driving mechanisms (Proga et al., 2000; Ramírez & Tombesi,
2012; Meena et al., 2021). In this case, two opposing forces control the
velocity of the outflowing gas as a function of distance: AGN-induced
radiative acceleration, and gravitational deceleration from the enclosed mass
in the host galaxy, including the SMBH (Meena et al., 2021). The resulting
equation, derived in full in Das et al. (2007), is

$v(r)=\sqrt{\int_{r_{1}}^{r}\left[4885\frac{L_{44}\mathcal{M}}{r^{2}}-8.6\times
10^{-3}\frac{M(r)}{r^{2}}\right]}dr$ (2)

where v(r) is the outflow velocity (in km s-1) of a cloud at a distance r (in
parsecs), L44 is the bolometric luminosity in $10^{44}$ erg s-1, $\mathcal{M}$
is the force multiplier, and $r_{1}$ is the launch distance of the cloud from
the central SMBH. For accelerated gas and dust, the force multiplier
($\mathcal{M}$) describes the ratio of the total absorption and scattering
cross-section to the Thomson cross-section. $M(r)$ is in the units of solar
masses (M⊙). The first term in the equation is the accelerative force, while
the second term is decelerative. Given the velocity and distance of a gas knot
from the SMBH, which has been corrected for projection effects, the launch
distance $r_{1}$ can be solved for numerically. Given fixed values for the
parameters in the above equation, we define the model turnover radius $r_{t}$
to be the distance from the SMBH at which the above two terms (radiative
acceleration and gravitational deceleration) are equal, which is also equal to
the maximum possible launch radius $r_{1}$ (Meena et al., 2023).

We can use the force multiplier $\mathcal{M}$ to specify how the efficiency of
radiative driving from bound-bound, bound-free, and free-free mechanisms
compares to that from pure Thomson scattering ($\mathcal{M}$ = 1) (Meena et
al., 2023; Castor et al., 1975; Abbott, 1982; Crenshaw et al., 2003; Trindade
Falcão et al., 2021b). $\mathcal{M}$ is affected by factors such as the
ionization parameter $U$ (which increases with decreasing $\mathcal{M}$ for
typical NLR gas) and the spectral energy distribution (SED) (Trindade Falcão
et al., 2021b). We use a force multiplier $\mathcal{M}$ = 500, which was found
to yield good agreement between modeled and observed turnover radii for a
sample of 7 AGN in Meena et al. (2023).

###  7.1 Estimates of Bolometric Luminosity

The AGN at the center of NGC 3227 has a variable luminosity, so the changing
L44 values will result in a range of possible turnover and launch radii.
Merritt (2022) finds a bolometric luminosity of $L_{\mathrm{Edd}}=1.41\times
10^{43}$ erg s-1 from determination of the optical flux at 5100 Å, which was
corrected for reddening of the Seyfert 1 nucleus (Crenshaw et al., 2001, EB-V
$=$ 0.18) and converted to bolometric luminosity through the calculation
$L_{\mathrm{bol}}=9.8\lambda L_{5100}$ (McLure & Dunlop, 2004). Assuming a
constant SMBH mass of $M_{BH}$ = 1.1 $\times 10^{7}$ M⊙ (Bentz et al., 2023),
the maximum possible luminosity of the AGN in NGC 3227 is given by the
Eddington limit as $L_{\mathrm{Edd}}=1.4\times 10^{45}$ erg s-1.

To obtain an average value of luminosity over the span of a decade, we
retrieved fluxes at 5100 Å from several observations of NGC 3227 (Denney et
al., 2010; De Rosa et al., 2018; Brotherton et al., 2020), including
spectrophotometric observations we obtained from Lowell with 2′′-wide slits on
five occasions. All of these observations were obtained between 2007 and 2017,
and the AGN flux at 5100 Å varied by a factor of 2.2 during this time. After
subtraction of the galaxy contribution from the above sources (6.8 $\times$
1015 erg s-1 cm-2), the same reddening and bolometric corrections as above,
and using a distance of 23.7 Mpc (Tonry et al., 2001; Blakeslee et al., 2001),
we determined an average bolometric luminosity of log
$L_{\mathrm{bol}}=4.78\times 10^{43}$ erg s-1 over 2007 – 2017.

For our analysis we also wish to obtain an average value for the bolometric
luminosity across the span of the NLR outflow, which has a light-travel time
of at least 2000 years. We therefore measured the integrated fluxes of [O III]
$\lambda$5007 in each of our 5 Lowell spectra obtained over 2009 – 2010 to
obtain an average value of 9.6 $\pm$ 2.3 $\times$ 10-13 erg s-1 cm-2 Å-1.
Utilizing the relationship $L_{\mathrm{bol}}=3500L_{5007}$ (Heckman et al.,
2004), we find an average bolometric luminosity of
$L_{\mathrm{bol}}=2.25\times 10^{44}$ erg s-1. Comparing the
$L_{\mathrm{bol}}$ value calculated from [O III] $\lambda$5007 emission, which
represents an average luminosity over at least 2,000 years, to that calculated
from 5100 Å emission, which shows emission over the recent period of 2007 –
2017, reveals that the brightness of the AGN has decreased by a factor of 8
over the last couple thousand years. Although the [O III] $\lambda$5007
emission does not reveal specific temporal information to provide a timeline
of when the dimming started, we can nevertheless confirm a substantial dimming
of the NLR over this time.

###  7.2 Launch Radii

We calculate a mass profile using the same technique described in Fischer et
al. (2017) and Meena et al. (2021), which uses Equation 4 of Terzić & Graham
(2005) to calculate the mass density distribution for individual Sérsic
components (Sersic, 1968) that include the host galaxy disk and bulge. We use
Equation 10 of Terzić & Graham (2005) and the mass density distribution to
determine the enclosed mass, and consequently gravitational deceleration, at a
given radius from the SMBH. Based on the known values of the bolometric
luminosity, enclosed mass and observed velocities at a observed distances
(corrected for outflow projection), we can derive the outflow velocity
profiles and numerically calculate the launch radii ($r_{1}$) of the observed
outflowing gas using Equation 2.

Figure 16: Velocity profiles showing the trajectories of radiatively driven
gas using Equation 2, a bolometric luminosity of L${}_{bol}=2.25\times
10^{44}$ erg s-1 cm-2, and a force multiplier of $\mathcal{M}=500$. The red
points represent kinematic data from KOSMOS, STIS, and NIFS whose distances
and velocities have been deprojected using the bicone model. The turnover
radius for these parameters is 31 pc.

Figure 16 shows how various launch radii will create different trajectories of
radiatively driven gas, where gas launched from closer to the SMBH can be
driven faster and to a greater distance than gas that is launched farther from
the SMBH. Using the average bolometric luminosity over the NLR
$L_{\mathrm{bol}}=2.25\times 10^{44}$ erg s-1 cm2, we find that the turnover
radius for these models ranges from $31-63$ pc for force multipliers ranging
from $\mathcal{M}=500-3000$ (see more discussion of $\mathcal{M}$ values in
Meena et al. (2023)). For comparison, the range of turnover radii is $13-28$
pc for the 2007 – 2017 luminosity of 4.78 $\times 10^{43}$ erg s-1 and
$44-224$ pc for the Eddington luminosity.

The data points in Figure 16 are distances and velocities of isolated
emission-line knots in the KOSMOS, STIS, and NIFS datasets, corrected for
projection effects with our bicone model. These knots, at current distances of
30 – 600 pc, can be tracked back to launch radii of 2 - 20 pc for the above
parameters, with the upper end close to the maximum launch radius of 31 pc.

According to the best-fit kinematic model described in Section 5.1, we find an
observed turnover radius of $26^{+6}_{-6}$ pc from a purely empirical fit to
the radial velocity profiles. Based on our dynamical calculations of radiative
driving by the AGN and gravitational deceleration from an enclosed mass model
of NGC 3227, which are independent of the observed kinematics, we find a model
turnover radius of $31-63$ pc for our NLR-averaged luminosity and force
multiplier of $\mathcal{M}=500-3000$. Thus, we find remarkable agreement
between observed and model turnover radii, indicating radiative driving and
gravitational deceleration are the dominant dynamical forces in the NLR of NGC
3227.

Figure 17: Adapted from Figure 10 of Meena et al. (2023). The model turnover
radii obtained from radiative-gravity formulism (Section 7) is compared to
observed velocity turnover radii determined from the geometry of the biconal
outflow model (Section 5.1), but with the addition of NGC 3227. The colors of
the points reflect the bolometric luminosity of each AGN taken from Meena et
al. (2023), underscoring their finding that brighter AGNs correspond to higher
turnover radii. As in Meena et al. (2023), vertical error bars for NGC 3227
arise from choosing lower and upper $\mathcal{M}$ values of 500 and 3000.
Horizontal errors are associated with the resolution element of STIS, which
was used for all measurements. The blue dashed line corresponds to unity,
where the modeled and observed turnover radii are equal.

###  7.3 Comparison to Past Results

Meena et al. (2023) examines the relationship between observed and model
turnover radii for the NLRs in eight Seyfert galaxies and find a strong
correlation, confirming that radiative driving alone is sufficient to produce
the highly accelerated gas clouds. Figure 17 shows the addition of NGC 3227 to
Figure 10 of Meena et al. (2023), providing another point at the low end of
the luminosity range (spanning 1043-46 erg s-1). The point lies close to the
dashed blue line showing unity between observed and modeled turnover radii,
further extending the strong relationship between these two independently
obtained values. As explained in Meena et al. (2023), the one discrepant point
is the low-luminosity AGN NGC 4051, and can be explained either by an
additional driving mechanism or by the inability of current telescopes to
resolve its turnover radius. For NGC 3227, as for most of the other AGN in
this plot, a force multiplier on the low end, at $\mathcal{M}=500$, provides
better agreement between model and observed turnover radii.

##  8 Conclusions

We observed the Seyfert 1 AGN NGC 3227 with the APO KOSMOS spectrograph and
Gemini NIFS IFU in the Z-band, and used those data alongside archival data
from HST, NIFS and ALMA to obtain ionized gas, molecular gas, and stellar
kinematic maps of the circumnuclear region and host galaxy disk. Our main
conclusions are as follows:

  1. 1.

We confirm the biconical outflowing structure of the ionized gas in the NLR of
NGC 3227, and improve upon the model established by previous works.. The
bicone has an inclination of 40${}^{+5}_{-4}$°with respect to our line of
sight, which is 25°steeper than the value reported in Fischer et al. (2013).
It has an inner half-opening angle of 47${}^{+6}_{-2}$°, which provides a
Seyfert 1 view as expected, and an outer half-opening angle of
68${}^{+1}_{-1}$°. These values place the bicone axis close to the galactic
plane, and explain the morphology of the NLR (especially the lack of [O III]
emission in the SW) as a result of extinction by dust in the plane. The dust
can be seen as multiple lanes, arcs, and spirals on both nuclear and galactic
scales, and is also responsible for reddening of the nucleus and NLR in the
optical (Crenshaw et al., 2001).

  2. 2.

We see ionized outflows traveling up to 500 km s-1 at distances as large as
7′′ (800 pc) from the SMBH. This is a significantly higher distance than was
recorded in Fischer et al. (2013), and although the emission is weak, it
extends beyond the modeled height of the bicone and is potentially disruptive
to star formation. Furthermore, we see disturbed ionized gas with large FWHM
out to a distance of 15′′ (1.7 kpc), which is not conducive to star formation.
The effective radius of the bulge is approximately 300 pc (Bentz & Manne-
Nicholas, 2018), and is unlikely to grow any further as long as it remains in
this disturbed state.

  3. 3.

We calculate the trajectories of radiatively driven gas from various launch
radii. Using a NLR-averaged bolometric luminosity of
$L_{\mathrm{bol}}=2.25\times 10^{44}$ erg s-1 cm-2, we find that outflows
propelled by radiative driving have a turnover radius ranging from $31-63$ pc,
depending on values for the force multiplier which we allow to range from
$\mathcal{M}=$ 500 – 3000. This range matches the value obtained from the
bicone model, 26${}^{+6}_{-6}$ pc, signaling agreement between our observed
turnover radius and that from the radiative-driving formalism described in
Meena et al. (2023). In further agreement with Meena et al. (2023), our
findings support radiative driving plus gravity as the dominant force behind
NLR outflows and additionally extend this result to the lower range of AGN
luminosity exhibited by NGC 3227. In general, this formalism works best for a
force multiplier of $\mathcal{M}=$ 500 .

  4. 4.

We see a correlation among the several phases of gas that we have analyzed.
Specifically, we note the presence of a bridge of gas centered around the
nucleus and extending $\sim$0$\farcs$5 ($\sim$60 pc) in both NW and SE
directions. This bridge is seen in He I, H2, and CO(2-1) and is perpendicular
to the outflowing axis, which may be the original (and potentially still
present) fueling flow to the AGN. Along the direction of the bicone axis, we
see [O III], [S III], He I, H2, and CO(2-1) emission with decreasing velocity
amplitudes in both the redshifted and blueshifted directions, consistent with
in situ heating, ionization and acceleration of gas from the cold gas
reservoir.

  5. 5.

Interestingly, our radiative driving calculations reveal that the launch
distances of the existing NLR emission-line knots lie in the 2 – 20 pc range.
In fact, if we operate within model parameters constrained by mass and NLR-
averaged luminosity, they cannot exceed 31 – 63 pc. This places the launch
radii of all of the NLR clouds within the bridge of gas seen in Figure 15,
which we have argued is the source of both the outflows and likely the
original fueling flow.

Further work will involve the use of CLOUDY (Ferland et al., 2013) to make
spatially-resolved mass loss profiles in the manner of Revalski et al. (2021,
2022). Together with spatially resolved maps of the cold gas, this will allow
us to create mass evacuation timescales that will provide a better picture of
how long it takes for the AGN in NGC 3227 to clear out surrounding material.
Performing these calculations will allow us to make inferences about NGC
3227’s ability to quench star formation in its central regions.

The authors would like to thank the anonymous referee for the constructive
feedback. J.F. would like to thank Dr. Almudena Alonso-Herrero for graciously
sharing her ALMA data on NGC 3227. J.F. would also like to thank Dr. Jan
Tobochnik for his helpful discussions regarding how to calculate the best
bicone model. R.A.R. acknowledges the support from Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq; Proj. 303450/2022-3,
403398/2023-1, & 441722/2023-7), Fundação de Amparo à pesquisa do Estado do
Rio Grande do Sul (FAPERGS; Proj. 21/2551-0002018-0), and CAPES (Proj.
88887.894973/2023-00). Many of the data presented in this work are based on
observations with the NASA/ESA Hubble Space Telescope and were obtained from
the Mikulski Archive for Space Telescopes (MAST), which is operated by the
Association of Universities for Research in Astronomy, Incorporated, under
NASA contract NAS5-26555. These observations are associated with program
number 16246. Support for program number 16246 was provided through a grant
from the STScI under NASA contract NAS5-26555. The specific observations used
in this work analyzed can be accessed via DOI: 10.17909/cm86-me24 (catalog
10.17909/cm86-me24). This research has made use of NASA’s Astrophysics Data
System. IRAF is distributed by the National Optical Astronomy Observatories,
which are operated by the Association of Universities for Research in
Astronomy, Inc., under cooperative agreement with the National Science
Foundation. This research has made use of the NASA/IPAC Extragalactic Database
(NED), which is operated by the Jet Propulsion Laboratory, California
Institute of Technology, under contract with the National Aeronautics and
Space Administration. Some of the observations used in this paper were
obtained with the Apache Point Observatory 3.5-meter telescope, which is owned
and operated by the Astrophysical Research Consortium.

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