11institutetext:  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69,
53121 Bonn, Germany
11email<EMAIL_ADDRESS>22institutetext: Astronomy Department, Faculty
of Science, King Abdulaziz University, P. O. Box 80203, Jeddah 21589, Saudi
Arabia 33institutetext: Xinjiang Astronomical Observatory, Chinese Academy of
Sciences, 830011 Urumqi, PR China 44institutetext: National Radio Astronomy
Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
55institutetext: Center for Astrophysics, Guangzhou University, 510006
Guangzhou, People’s Republic of China 66institutetext: School of Astronomy and
Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing 210023,
People’s Republic of China 77institutetext: Key Laboratory of Modern Astronomy
and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210023,
People’s Republic of China

# Discovery of ammonia (9,6) masers in two high-mass star-forming regions

Y. T. Yan (闫耀庭) , Member of the International Max Planck Research School
(IMPRS) for Astronomy and Astrophysics at the universities of Bonn and
Cologne.Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
C. Henkel Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
K. M. Menten Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
Y. Gong (龚龑) Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
J. Ott Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
T. L. Wilson Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
A. Wootten Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
A. Brunthaler Discovery of ammonia (9,6) masers in two high-mass star-forming
regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming regions
J. S. Zhang (张江水) Discovery of ammonia (9,6) masers in two high-mass star-
forming regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming
regions J. L. Chen (陈家梁) Discovery of ammonia (9,6) masers in two high-mass
star-forming regionsDiscovery of ammonia (9,6) masers in two high-mass star-
forming regions K. Yang (杨楷) Discovery of ammonia (9,6) masers in two high-
mass star-forming regionsDiscovery of ammonia (9,6) masers in two high-mass
star-forming regionsDiscovery of ammonia (9,6) masers in two high-mass star-
forming regionsDiscovery of ammonia (9,6) masers in two high-mass star-forming
regions

(Received 13 December 2021 / Accepted 30 December 2021)

###### Abstract

Context. Molecular maser lines are signposts of high-mass star formation,
probing the excitation and kinematics of very compact regions in the close
environment of young stellar objects and providing useful targets for
trigonometric parallax measurements.

Aims. Only a few NH3 (9,6) masers are known so far, and their origin is still
poorly understood. Here we aim to find new NH3 (9,6) masers to provide a
better observational basis for studying their role in high-mass star-forming
regions.

Methods. We carried out NH3 (9,6) observations toward Cepheus A and
G34.26$+$0.15 with the Effelsberg 100-meter telescope (beam size 49″) and the
Karl G. Jansky Very Large Array (JVLA; beam size about
1$\aas@@fstack{\prime\prime}$2).

Results. We discovered new NH3 (9,6) masers in Cep A and G34.26$+$0.15, which
increases the number of known high-mass star-forming regions hosting NH3 (9,6)
masers from five to seven. Long-term monitoring (20 months) at Effelsberg
shows that the intensity of the (9,6) maser in G34.26$+$0.15 is decreasing,
while the Cep A maser remains stable. Compared to the Effelsberg data and
assuming linear variations between the epochs of observation, the JVLA data
indicate no missing flux. This suggests that the NH3 (9,6) emission arises
from single compact emission regions that are not resolved by the
interferometric measurements. As JVLA imaging shows, the NH3 (9,6) emission in
Cep A originates from a sub-arcsecond-sized region, slightly to the west
($0\aas@@fstack{\prime\prime}28\pm 0\aas@@fstack{\prime\prime}10$) of the peak
position of the 1.36 cm continuum object, HW2. In G34.26$+$0.15, three NH3
(9,6) maser spots are observed: one is close to the head of the cometary
ultracompact H II region C, and the other two are emitted from a compact
region to the west of the hypercompact H II region A.

Conclusions. The newly found (9,6) masers appear to be related to outflows.
The higher angular resolution of JVLA and very long baseline interferometry
observations are needed to provide more accurate positions and constraints for
pumping scenarios.

###### Key Words.:

Masers – ISM: clouds – ISM: individual objects: Cep A, G34.26$+$0.15 – ISM: H
II regions – Radio lines: ISM

##  1 Introduction

Since its discovery more than five decades ago (Cheung et al., 1968), ammonia
(NH3) has been a most valuable molecule for investigating the physical
properties of molecular clouds (e.g., Ho & Townes, 1983). While thermally
excited transitions in the centimeter-wavelength inversion transitions of
ammonia are regarded as a reliable thermometer of molecular clouds (e.g.,
Walmsley & Ungerechts, 1983; Danby et al., 1988), ammonia masers have
attracted attention since the first detection of maser action in the $(J,K)$ =
(3,3) metastable ($J=K$) line toward the massive star-forming region W33
(Wilson et al., 1982). Subsequent observations have led to the detection of
new metastable ammonia masers, including 15NH3 (3,3) (Mauersberger et al.,
1986), NH3 (1,1) (Gaume et al., 1996), NH3 (2,2) (Mills et al., 2018), NH3
(5,5) (Cesaroni et al., 1992), NH3 (6,6) (Beuther et al., 2007), NH3 (7,7),
NH3 (9,9), and NH3 (12,12) (Henkel et al., 2013). These have led to the
discovery of metastable maser lines in 22 different regions (Mauersberger et
al., 1986, 1987; Wilson & Henkel, 1988; Wilson et al., 1990; Pratap et al.,
1991; Cesaroni et al., 1992; Wilson & Schilke, 1993; Mangum & Wootten, 1994;
Kraemer & Jackson, 1995; Zhang & Ho, 1995; Zhang et al., 1999; Walsh et al.,
2007; Hunter et al., 2008; Galván-Madrid et al., 2009; Brogan et al., 2011;
Urquhart et al., 2011; Walsh et al., 2011; Wang et al., 2012; Henkel et al.,
2013; Hoffman & Joyce, 2014; McEwen et al., 2016; Mills et al., 2018; Hogge et
al., 2019; Mei et al., 2020; Towner et al., 2021). Compared with the
metastable ammonia masers, detected non-metastable ($J>K$) ammonia maser
transitions are more numerous. The first highly excited non-metastable ammonia
maser was detected by Madden et al. (1986) in the $(J,K)$ = (9,6) and (6,3)
lines. Thereafter, many other NH3 non-metastable inversion transition lines
have been identified as masers, including the (5,3), (5,4), (6,1), (6,2),
(6,4), (6,5), (7,3), (7,4), (7,5) (7,6), (8,3), (8,4), (8,5), (8,6), (9,3),
(9,4), (9,5), (9,7), (9,8), (10,7), (10,8), (10,9), and (11,9) transitions
(e.g., Mauersberger et al., 1987, 1988; Walsh et al., 2007; Henkel et al.,
2013; Mei et al., 2020). Except for the NH3 (3,3) masers proposed to be
associated with four supernova remnants (McEwen et al., 2016), almost all the
other ammonia masers are detected in high-mass star-forming regions (HMSFRs).
However, while many HMSFRs host water (H2O), hydroxyl (OH), or methanol
(CH3OH) masers, ammonia masers are quite rare in these sources, and the role
that the environment of a young high-mass star plays in their excitation
remains unclear. Therefore, dedicated searches for ammonia masers in HMSFRs
are indispensable in regard to their overall incidence and association with
different environments, which can provide additional constraints on the
pumping mechanism of ammonia masers.

So far, a total of 32 NH3 inversion transitions ($\Delta K$ = 0 and $\Delta J$
= 0) have been identified as masers. Among these, and despite arising from
energy levels as high as 1090 K above the ground state, the NH3 (9,6) maser
stands out as being the strongest and most variable one in W51-IRS2 (e.g.,
Henkel et al., 2013). Maser emission in this line has only been detected in
five HMSFRs, W51, NGC7538, W49, DR21 (OH) (Madden et al., 1986), and Sgr B2(N)
(Mei et al., 2020). The NH3 (3,3) masers are thought to be collisionally
excited (e.g., Flower et al., 1990; Mangum & Wootten, 1994); in contrast, the
pumping mechanism of NH3 (9,6) masers is less well constrained (Madden et al.,
1986). Brown & Cragg (1991) have studied ortho-ammonia and found that it could
possibly pump the (6,3) inversion line, but they did not extend their model to
the (9,6) transition due to the fact that collision rates are only known for
inversion levels up to $J\leavevmode\nobreak\ =\leavevmode\nobreak\ 6$ (e.g.,
Danby et al. 1988).

NH3 (9,6) masers are found to be strongly variable, similar to H2O masers
(Madden et al. 1986; Pratap et al. 1991; Henkel et al. 2013). In W51-IRS2,
Henkel et al. (2013) found that the (9,6) line showed significant variation in
line shape within a time interval of only two days. Mapping of the (9,6) maser
toward W51 with very long baseline interferometry (VLBI) suggests that the
masers are closer to the H2O masers than to the OH masers or to ultracompact
(UC) H II regions (Pratap et al., 1991). While Henkel et al. (2013) and Goddi
et al. (2015) showed that the SiO and NH3 masers in W51-IRS2 are very close to
each other, their positions, differing by 0$\aas@@fstack{\prime\prime}$065
($\sim$0.015 pc), do not fully coincide.

In this paper we report the discovery of NH3 (9,6) masers in two HMSFRs,
Cepheus A and G34.26$+$0.15. This increases the number of (9,6) maser
detections in our Galaxy from five to seven. In Sect. 2 observations with the
Effelsberg 100-meter telescope and the Karl G. Jansky Very Large Array (JVLA)
are described. Results are presented in Sect. 3. The morphology of Cep A and
G34.26$+$0.15 as well as a comparison of the emission distributions of
different tracers with the NH3 (9,6) masers are presented in Sect. 4. Our main
results are summarized in Sect. 5.

##  2 Observations and data reduction

###  2.1 Effelsberg observations and data reduction

The NH3 (9,6) line was observed toward Cep A and G34.26$+$0.15 with the
100-meter Effelsberg telescope111Based on observations with the 100-meter
telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at
Effelsberg. in 2020 January and 2021 February, July, and August. The S14mm
double beam secondary focus receiver was employed. The full width at half
maximum (FWHM) beam size is 49$\arcsec$ at 18.5 GHz, the frequency of the
target line. The observations were performed in position switching mode, and
the off position was 10$\arcmin$ in azimuth away from the source. For
observations made before 2021 August, we used a spectrometer that covered 2
GHz wide backends with a channel width of 38.1 kHz, corresponding to
$\sim$0.62 km s-1 at the line’s rest frequency, 18.49939 GHz (Poynter & Kakar,
1975). A high spectral resolution backend with 65536 channels and a bandwidth
of 300 MHz was employed in 2021 August, providing a channel width of 0.07 km
s-1 at 18.5 GHz. Pointing was checked every 2 hours using 3C 286 or NGC 7027.
Focus calibrations were done at the beginning of the observations and during
sunset and sunrise toward the abovementioned pointing sources. The system
temperatures were 100–130 K on a main-beam brightness temperature, $T_{\rm
MB}$, scale. This flux density was calibrated assuming a $T_{\rm MB}/S$ ratio
of 1.95 K/Jy, derived from continuum cross scans of NGC 7027 (the flux density
was adopted from Ott et al. 1994). Calibration uncertainties are estimated to
be $\sim 10$%.

We used the GILDAS/CLASS222https://www.iram.fr/IRAMFR/GILDAS/ package (Pety,
2005) to reduce the spectral line data. A first-order polynomial was
subtracted from each spectrum for baseline removal.

###  2.2 JVLA observations and data reduction

Observations of the NH3 (9,6) line toward Cep A and G34.26$+$0.15 were
obtained on 2021 July 13 with the JVLA of the National Radio Astronomy
Observatory333The National Radio Astronomy Observatory is a facility of the
National Science Foundation operated under cooperative agreement by Associated
Universities, Inc. (NRAO) in the C configuration (project ID: 21A-157, PI:
Yaoting Yan). We employed 27 antennas for the observations. The primary beam
of the JVLA antennas is $150^{\prime\prime}$ (FWHM) at 18.5 GHz. A mixture of
mixed three-bit and eight-bit samplers were used to perform the observations.
For the NH3 (9,6) line observations, we used one subband with the eight-bit
sampler covering a bandwidth of 16 MHz with full polarization, eight
recirculations, and four baseline board pairs (BIBPs) to provide a velocity
range of 260 km s-1 with a channel spacing of 0.13 km s-1. Two additional
subbands of bandwidth 16 MHz were used to cover the NH3 (8,5) and (10,7)
lines. The three-bit sampler with 32 subbands, each with a bandwidth of 128
MHz to cover a total range of 4 GHz between 20–24 GHz, was used to measure the
continuum emission. 3C 286 with a flux density of 2.89 Jy at 18.5 GHz (Perley
& Butler, 2013) was used as a calibrator for pointing, flux density, bandpass,
and polarization. J2230+6946 and J1851+0035 served as gain calibrators for Cep
A and G34.26$+$0.15, respectively. The on-source times were 4m30s and 4m50s
toward Cep A and G34.26$+$0.15, respectively.

Data from two antennas were lost due to technical issues. The data from the
remaining 25 antennas were reduced through the Common Astronomy Software
Applications package (CASA444https://casa.nrao.edu/; McMullin et al. 2007). We
calibrated the data with the JVLA CASA calibration pipeline using CASA 6.1.2.
The results were obtained after flagging data that contain artifacts. We
inspected the phase, amplitude, and bandpass variations of the calibrated
visibility data to search for additional artifacts before imaging. Then, the
uvcontsub task in CASA was used to separate the calibrated visibilities into
two parts, one with line-only data and the other with the continuum data. The
tclean task with a cell size of 0$\aas@@fstack{\prime\prime}$2 and Briggs
weighting with robust=0 was used to produce the images of spectral line and
continuum emission. The synthesized beams for NH3 (9,6) are
$1\aas@@fstack{\prime\prime}47\times 0\aas@@fstack{\prime\prime}99$ at P.A. =
$58\aas@@fstack{\circ}79$ and $1\aas@@fstack{\prime\prime}33\times
1\aas@@fstack{\prime\prime}06$ at P.A. = $5\aas@@fstack{\circ}36$ toward Cep A
and G34.26$+$0.15, respectively. For the 1.36 cm (20–24 GHz) continuum
emission, the synthesized beams are $1\aas@@fstack{\prime\prime}08\times
0\aas@@fstack{\prime\prime}67$ at P.A. = $60\aas@@fstack{\circ}64$ and
$0\aas@@fstack{\prime\prime}95\times 0\aas@@fstack{\prime\prime}71$ at P.A. =
$5\aas@@fstack{\circ}91$ toward Cep A and G34.26$+$0.15. The typical absolute
astrometric accuracy of the JVLA is $\sim$10% of the synthesized
beam555https://science.nrao.edu/facilities/vla/docs/manuals/oss/performance-/positional-
accuracy. The flux density scale calibration accuracy is estimated to be
within 15%.

Figure 1: Spectra from NH3 (9,6) transition lines. Left: Top to bottom: Time
sequence of NH3 (9,6) profiles observed toward Cep A with the Effelsberg
100-meter telescope (after subtracting a first-order polynomial baseline). A
JVLA spectrum is interspersed. The systemic velocity from CO and HCO+ lines is
indicated by a dashed blue line. The two dashed red lines at LSR velocities,
$V_{\rm LSR}$, of $-$0.90 km s-1 and $-$0.28 km s-1 indicate the central
velocities of the two major components. Right: NH3 (9,6) spectra from
G34.26$+$0.15. The systemic velocity from C17O is indicated by a dashed blue
line. The three dashed red lines at $V_{\rm LSR}$ = 54.1 km s-1, 55.8 km s-1,
and 62.5 km s-1 show the central velocities of the main ammonia emission
components.

Figure 2: NH3 (9,6) line profiles emphasizing, in contrast to the spectra in
Fig. 1, weaker features. Cep A spectra are presented on the left,
G34.26$+$0.15 spectra on the right. The two dashed red lines in the left
panels indicate $V_{\rm LSR}$ = 1.48 km s-1 and 2.89 km s-1. In the right
panels, the two dashed red lines refer to 54.1 km s-1 and 55.8 km s-1.

##  3 Results

The spectra from different epochs are shown in Figs. 1 and 2. Toward Cep A,
the NH3 (9,6) line profile from the JVLA is extracted from an Effelsberg-beam-
sized region (FWHM, 49$\arcsec$). In the case of G34.26$+$0.15, the NH3
spectrum is below the noise level if a similarly large beam size is used.
Therefore, we derived the JVLA NH3 (9,6) spectrum from a smaller region, with
radius 3$\aas@@fstack{\prime\prime}$5, that contains all the detected NH3
(9,6) emission. In Table 1, the observed NH3 (9,6) line parameters obtained by
Gaussian fits are listed. NH3 (8,5) and (10,7) emission is not detected by our
JVLA observations. The 3$\sigma$ upper limits for the NH3 (8,5) and (10,7)
lines toward Cep A are 23.2 mJy beam-1 and 27.2 mJy beam-1, respectively. In
G34.26$+$0.15, the corresponding 3$\sigma$ upper limits for the NH3 (8,5) and
(10,7) lines are 22.1 mJy beam-1 and 30.4 mJy beam-1. For both sources,
sensitivity levels refer to emission from a single channel of width 0.13 km
s-1. Taking the larger measured line widths of the (9,6) maser features (see
Table 1), these limits could be further lowered by factors of two to four.

###  3.1 Centimeter-continuum emission

The 1.36 cm continuum, derived from our JVLA observations, toward Cep A is
presented in Fig. 3. Six published compact sources, HW2, HW3a, HW3b, HW3c,
HW3d, and HW9, are detected in our observations. Figure 4 shows the 1.36 cm
continuum in G34.26$+$0.15. Three main continuum objects, A, B, and C, are
detected. By using the imfit task in CASA, we measured the continuum flux at
1.36 cm toward individual compact source components in Cep A and
G34.26$+$0.15. Details are given in Table 2.

Figure 3: Cepheus A. White contours mark the 1.36 cm JVLA continuum map of Cep
A; levels are $-$5, 5, 10, 20, 30, 40, 50, 70, 90, and 110 $\times$ 0.125 mJy
beam-1. The background image is the Spitzer 4.5$\,\mu\rm{m}$ emission, taken
from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE;
Benjamin et al., 2003; Churchwell et al., 2009). The reference position is
$\alpha_{\rm J2000}$ = 22h56m17$\aas@@fstack{s}$972, and $\delta_{\rm J2000}$
= 62$\degr$01$\arcmin$49$\aas@@fstack{\prime\prime}$587, the peak position of
the continuum map, is marked with a black cross. Slightly to the west of the
cross is the black ellipse denoting the position of the NH3 (9,6) emission
with a purple star at its center. OH (Bartkiewicz et al., 2005), H2O (Sobolev
et al., 2018), and CH3OH (Sanna et al., 2017) masers are presented as
diamonds, circles, and squares, respectively. The color bar on the right-hand
side indicates the LSR velocity range of the maser spots. Figure 4: 1.36 cm
JVLA continuum map of G34.26$+$0.15 presented as white contours with levels of
$-$5, 5, 10, 20, 30, 40, 50, 70, 90, 110, 130, 150, 180, and 200 $\times$ 5.0
mJy beam-1. The background image is the Spitzer 4.5$\,\mu\rm{m}$ emission,
taken from GLIMPSE. The reference position is $\alpha_{\rm J2000}$ =
18h53m18$\aas@@fstack{s}$560, and $\delta_{\rm J2000}$ =
01$\degr$14$\arcmin$58$\aas@@fstack{\prime\prime}$201, the peak position, is
marked by a black cross. The black ellipses show the positions of NH3 (9,6)
emissions with stars at their center (i.e., M1, M2, and M3). OH (Zheng et al.,
2000), H2O (Imai et al., 2011), and CH3OH (Bartkiewicz et al., 2016) masers
are presented as diamonds, circles, and squares, respectively. The color bar
indicates the velocity range ($V_{\rm LSR}$) of maser spots.

###  3.2 NH3 (9,6) emission in Cep A

In 2020 January, NH3 (9,6) emission with a peak flux density of 0.67 $\pm$
0.07 Jy was first detected with the Effelsberg 100-meter telescope in Cep A.
Emission with similar strength was also detected in 2021 February and August
with the same telescope. Higher velocity resolution data, which were obtained
in 2021 August, again with the Effelsberg 100-meter telescope, show that the
(9,6) emission contains two main velocity components. Overall, the flux
densities of the NH3 (9,6) emission line measured with the Effelsberg
100-meter telescope are, within the calibration uncertainties, unchanged. This
is valid for the time interval between 2020 January and August 2021, when we
smoothed the obtained spectra to the same velocity resolution. We also see
another two weaker components. Figure 2 emphasizes these weak components with
an expanded flux density scale.

Higher angular resolution data from the JVLA pinpoint the position of the NH3
(9,6) emission with an offset of ($-0\aas@@fstack{\prime\prime}$28,
$0\aas@@fstack{\prime\prime}$02) relative to the 1.36 cm continuum peak of Cep
A HW2 (Fig. 3). The deconvolved NH3 (9,6) component size is
$(0\aas@@fstack{\prime\prime}29\pm
0\aas@@fstack{\prime\prime}15)\times(0\aas@@fstack{\prime\prime}19\pm
0\aas@@fstack{\prime\prime}14)$ at P.A. = $174\degr$, derived with the imfit
task in CASA, and can thus be considered, accounting for the uncertainties, as
unresolved.

In view of the constancy of the flux densities obtained at Effelsberg and the
similar JVLA flux density, measured in 2021 July, there is no missing
interferometric flux density in the JVLA data.

###  3.3 NH3 (9,6) emission in G34.26$+$0.15

The NH3 (9,6) emission was first detected toward G34.26$+$0.15 in 2020 January
with the Effelsberg 100-meter telescope. Higher velocity resolution data from
2021 August show the NH3 (9,6) emission to be composed of two different
components. The spectra of weak components on a smaller flux density scale are
presented in Fig. 2.

Three different locations showing NH3 (9,6) emission are found toward
G34.26$+$0.15 (Fig. 4). The deconvolved NH3 (9,6) component sizes are
$(1\aas@@fstack{\prime\prime}42\pm
0\aas@@fstack{\prime\prime}43)\times(0\aas@@fstack{\prime\prime}54\pm
0\aas@@fstack{\prime\prime}62)$ at P.A. = $97\degr$ (M1),
$(0\aas@@fstack{\prime\prime}42\pm
0\aas@@fstack{\prime\prime}27)\times(0\aas@@fstack{\prime\prime}15\pm
0\aas@@fstack{\prime\prime}27)$ at P.A. = $150\degr$ (M2), and
$(1\aas@@fstack{\prime\prime}17\pm
0\aas@@fstack{\prime\prime}34)\times(0\aas@@fstack{\prime\prime}27\pm
0\aas@@fstack{\prime\prime}46)$ at P.A. = $53\degr$ (M3) and are thus
comparable to or smaller than the beam size.

Overall, the NH3 (9,6) line from G34.26$+$0.15 weakened during the time
interval from 2020 January to 2021 August by about 70%. A comparison between
the JVLA spectrum and the Effelsberg data, assuming a linear decrease in the
integrated intensity as a function of time between different epochs of the
100-meter observations, suggests there is no missing flux in the JVLA data.
This is similar to the situation in Cep A.

##  4 Discussion

###  4.1 Morphology of Cep A and G34.26$+$0.15

Cep A, at a trigonometric parallax distance of 0.70$\pm$0.04 kpc (Moscadelli
et al., 2009; Dzib et al., 2011), is the second closest HMSFR (after Orion)
and by far the closest NH3 (9,6) maser known. About 16 compact
($\sim$1$\arcsec$) radio sources (e.g., Hughes & Wouterloot, 1984; Hughes,
1991; Garay et al., 1996) have been identified in Cep A. Hughes & Wouterloot
(1984) discovered these targets at radio wavelengths, which are UC and
hypercompact (HC) H II regions and/or stellar wind sources, subsequently named
as HW sources. The HW2 object is one of the best known examples of a
protostellar jet or disk system driving a powerful outflow (e.g., Rodriguez et
al., 1980; Güsten et al., 1984; Torrelles et al., 1986; Curiel et al., 2006;
Carrasco-González et al., 2021). The observed NH3 (9,6) emission is slightly
offset ($-0\aas@@fstack{\prime\prime}$28, $0\aas@@fstack{\prime\prime}$02)
from the center of HW2 (see Fig. 3).

G34.26$+$0.15 is an HMSFR located at a distance of 3.3 kpc (Kuchar & Bania,
1994). It hosts four radio continuum components named A, B, C, and D.
Component C is a prototypical cometary UC H II region containing a compact
head and a diffuse tail that extends from east to west (e.g., Reid & Ho, 1985;
Garay et al., 1986; Sewilo et al., 2004; Sewiło et al., 2011). Components A
and B are HC H II regions, located to the east of component C. An extended
ring-like H II region, called component D, is located southeast of components
A-C. One of the three observed NH3 (9,6) emission line sources, M1, is close
to the head of component C, whereas M2 and M3 originate from another compact
region in the west of the HC H II component A (see Fig. 4).

###  4.2 NH3 (9,6) emission possibly caused by maser action

As shown in Fig. 1, the NH3 (9,6) profiles in Cep A and G34.26$+$0.15 are
narrow ($\Delta V_{1/2}\leq$2.0 km s-1), much narrower than the expected line
widths ($\gtrsim$4 km s-1) of thermal lines observed at a similar angular
resolution (e.g., Torrelles et al., 1985, 1986, 1993, 1999; Henkel et al.,
1987; Comito et al., 2007; Mookerjea et al., 2007; Wyrowski et al., 2012;
Beuther et al., 2018). Velocity shifts with respect to the systemic velocities
of the two sources are both observed, that is, $V\sim$10 km s-1 in Cep A and
$V\sim$4 km s-1 in G34.26$+$0.15 (see details in Sect. 4.3). Furthermore, time
variability is observed in the case of G34.26$+$0.15, which is also a
characteristic feature of maser emission.

Additional evidence of their maser nature is the high brightness temperatures
of the (9,6) emission spots toward Cep A and G34.26$+$0.15. The spectral
parameters are listed in Table 3. Because at least a significant part of the
NH3 (9,6) emission is not resolved by our JVLA observations, the derived
brightness temperatures are only lower limits. Nevertheless, the lower limits
on the brightness temperature are $>$800 K in Cep A (see Table 3), which is
much higher than the expected thermal gas temperature of $\sim$250 K (e.g.,
Patel et al., 2005; Comito et al., 2007; Beuther et al., 2018). This strongly
suggests that the NH3 (9,6) emission in Cep A is due to maser action. Because
G34.26+0.15 is located at about five times the distance to Cep A, beam
dilution effects reduce the lower main beam brightness temperature limit to
400 K in G34.26$+$0.15 (M2) (see Table 3). We also note that the luminosity of
the NH3 (9,6) emission in G34.26$+$0.15 is higher than or comparable to that
in Cep A, depending on the epoch of our observations.

Finally, the non-detections of the (8,5) and (10,7) lines also indicate that
the (9,6) line is special. This allows us to derive lower 3$\sigma$ limits of
the (9,6)/(8,5) and (9,6)/(10,7) line intensity ratios. The (9,6) line arises
from ortho-NH3 ($K=3n$), whereas the NH3 (8,5) and (10,7) lines are para-NH3
($K\neq 3n$) lines. The minimum ortho-to-para ratios are in the range 12–42
and 1–8 toward Cep A and G34.26$+$0.15, respectively. The statistical weights
for the ortho states are twice as large as those for the para states (e.g.,
Umemoto et al., 1999; Goddi et al., 2011; Henkel et al., 2013). In Cep A, the
line intensity ratios are far higher than this factor of two. Thus, at least
in Cep A the higher main beam brightness peak temperature of the (9,6)
emission is caused by maser action, perhaps involving exponential
amplification, and the case of G34.26$+$0.15 is likely similar.

###  4.3 Comparison of NH3 (9,6) masers with previously published
(quasi-)thermal NH3 emission

The metastable (1,1), (2,2), (3,3), and (4,4) ammonia lines show thermal
emission toward Cep A over a velocity range of $-$13 km s${}^{-1}\leq V_{\rm
LSR}\leavevmode\nobreak\ \leq-$4 km s-1 (Brown et al., 1981; Güsten et al.,
1984; Torrelles et al., 1985, 1986, 1993, 1999). An average NH3 column density
of $\sim$5$\times$1015 cm-2 was estimated for a region of 3″ around HW2
(Torrelles et al., 1999). This high NH3 abundance could provide a suitable
environment for maser species. Large line widths ($\Delta V_{1/2}\simeq$7.0 km
s-1) with $V_{\rm LSR}\sim\leavevmode\nobreak\ -$10 km s-1 in both (1,1) and
(2,2) lines were found toward HW2 (Torrelles et al., 1993). The velocity is
similar to the cloud’s systemic local standard of rest (LSR) velocity of
$-11.2$ km s-1, which is based on CO (Narayanan & Walker, 1996) and HCO+
observations (Gómez et al., 1999). Our (9,6) maser is redshifted ($-$0.9 km
s${}^{-1}\leq V_{\rm LSR}\leavevmode\nobreak\ \leq$2.9 km s-1) and shares
positions with the outflowing gas seen in CO and HCO+ with similarly
redshifted velocities. Therefore, we argue that the (9,6) masers are related
to outflowing gas.

In G34.26$+$0.15, a large NH3 column density, 1018.5±0.2 cm-2, and a kinetic
temperature of 225$\pm$75 K were derived by Henkel et al. (1987) based on
measurements of 15 NH3 inversion transitions in the frequency range of
22.0–26.0 GHz. These did not include the (9,6) transition. While these lines
were measured with a beam size of about 40$\arcsec$, a comparison of the peak
intensities of the optically thick lines with the kinetic temperature reveals
the size of the hot, ammonia-emitting core to be only $\sim$2.5$\arcsec$. All
those measured NH3 lines were quasi-thermal and had LSR velocities of
$\sim\leavevmode\nobreak\ $58.5 km s-1, close to the systemic velocity of
$\sim\leavevmode\nobreak\ $58.1 km s-1 obtained from C17O observations
(Wyrowski et al., 2012). Their line widths ($\Delta V_{1/2}\geq$3.6 km s-1)
are larger than what we find (0.35 km s${}^{-1}\leq\Delta V_{1/2}\leq$ 0.94 km
s-1) for each (9,6) maser component (see details in Table 3). In all, we may
have observed four different (9,6) velocity features. Three are blueshifted at
$V_{\rm LSR}\leavevmode\nobreak\ \sim\leavevmode\nobreak\ $53.8 km s-1, 55.8
km s-1, and 56.8 km s-1, and a fourth, tentatively detected, at 62.5 km s-1.
This tentative redshifted feature was only potentially detected with
Effelsberg in 2020 January. The velocity is similar to that of the JVLA
measurements on the NH3 (1,1) absorption line against continuum source C
($\sim 7\arcsec$ resolution; Keto et al., 1987) and the NH3 (3,3) emission
surrounding continuum source B as well as the head of C
(1$\aas@@fstack{\prime\prime}$4$\times$1$\aas@@fstack{\prime\prime}$2
resolution; Heaton et al., 1989). However, we did not find this redshifted
component in our JVLA observations. Therefore, its position within
G34.26$+$0.15 cannot be determined. The blueshifted (9,6) masers with a
velocity range of 53.8–56.8 km s-1 (M1, M2, and M3) show velocities compatible
with those of the NH3 (3,3) emission at the proper positions (Heaton et al.,
1989), which might be a suitable environment for maser species.

###  4.4 Comparison of NH3 (9,6) masers with other maser lines

To characterize the environment of NH3 (9,6) masers, we can compare their
positions with respect to those of other maser species (i.e., OH, H2O, and
CH3OH). Toward Cep A HW2, many CH3OH (e.g., Menten, 1991; Sugiyama et al.,
2008; Sanna et al., 2017) and H2O maser spots (e.g., Torrelles et al., 1998,
2011; Sobolev et al., 2018) are detected and are associated with its disk.
Sobolev et al. (2018) also found that most of the H2O maser flux is associated
with the compact H II region HW3d. OH maser features close to the H II regions
are also seen in HW2 (e.g., Cohen & Brebner, 1985; Bartkiewicz et al., 2005).
These three kinds of masers in Cep A have a large velocity range of $-$25 km
s${}^{-1}\leq V_{\rm LSR}\leavevmode\nobreak\ \leq-$2 km s-1 and are
widespread around HW2 and HW3, while NH3 (9,6) emission is only detected at
$-$0.9 km s${}^{-1}\leq V_{\rm LSR}\leavevmode\nobreak\ \leq$2.9 km s-1 toward
a sub-arcsecond-sized region to the west of the peak continuum position of HW2
(see Fig. 3). This suggests that the NH3 (9,6) maser in Cep A is unique and
not related to maser spots seen in other molecular species.

In G34.26$+$0.15, OH (Zheng et al., 2000), H2O (Imai et al., 2011), and CH3OH
(Bartkiewicz et al., 2016) masers have been detected east of source C (Fig.
4), and none of them coincides with the head of C. The NH3 (9,6) maser M1 is
also found slightly off the head of source C. This could suggest that M1 is
powered by continuum source C or by an outflow. Near component B, there are
some OH and CH3OH masers but no H2O or NH3 masers. A group of H2O masers,
well-known tracers of outflows, with a large velocity distribution of 43 km
s${}^{-1}\leq V_{\rm LSR}\leavevmode\nobreak\ \leq$54 km s-1, was found to the
west of the centimeter-continuum source A and close to the peak of the
millimeter-continuum emission (see details in our Fig. 6 and also in Fig. 5 of
Imai et al. 2011). The closeness of NH3 (9,6) maser spots M2 and M3 to this
group of water masers and their similar velocities again suggest an
association of NH3 (9,6) masers with outflow activity.

###  4.5 Constraints on pumping scenarios

Our observations have resulted in the detection of NH3 (9,6) masers in Cep A
and G34.26$+$0.15. The new detections could provide additional constraints on
the maser line’s pumping mechanism. As mentioned in Sect. 1, the pumping
mechanism of the (9,6) maser is unclear (Madden et al., 1986; Brown & Cragg,
1991). Previous studies have suggested that there are three main pumping
scenarios to explain the observed NH3 maser lines (Madden et al., 1986; Henkel
et al., 2013): (1) infrared radiation from the dust continuum emission, (2)
line overlap, and (3) collisional pumping.

For the first mechanism, infrared photons near 10 $\mu$m are needed for
vibrational excitation. The high dust temperature ($\sim$300 K) of W51-IRS2
can provide substantial infrared photons near 10 $\mu$m, which is used for
radiative pumping (Henkel et al., 2013). Both Cep A and G34.26$+$0.15 have
similar kinetic temperatures of $\gtrsim$200 K (Henkel et al., 1987; Patel et
al., 2005; Comito et al., 2007; Beuther et al., 2018). This suggests that high
kinetic temperatures are needed to excite NH3 (9,6) masers. However, it should
be noted that the silicate dust absorption feature might dominate at 10 $\mu$m
(see the spectral energy distribution of Cep A in De Buizer et al. 2017).
Additionally, there is no bright infrared emission around the two (9,6)
masers, M2 and M3, in G34.26$+$0.15 (see Fig. 4; see also Fig. 11 in De Buizer
et al. 2003 for a 10.5 $\mu$m map). This indicates that the pumping mechanism
via infrared photons near 10 $\mu$m may not be viable to explain the (9,6)
masers in Cep A and G34.26$+$0.15. Furthermore, Wilson & Schilke (1993) argued
that radiative pumping by dust emission tends to excite multiple adjacent
ammonia maser transitions, which appears to contradict our failure to detect
the adjacent (8,5) and (10,7) lines (with respect to quantum numbers and
frequency) and to only measure the (9,6) transitions in Cep A and
G34.26$+$0.15. Therefore, we suggest that infrared radiation from dust is not
the main pumping source.

Madden et al. (1986) suggested that there might be some line overlaps between
the rotational NH3 transitions in the far-infrared band. However, this would
be unlikely to affect only the (9,6) line. Nevertheless, far-infrared spectral
observations will be needed to clarify this scenario.

Based on our observations, the (9,6) maser spots are close to, but not
coincident with, the peaks of the radio continuum emission in Cep A and
G34.26$+$0.15. Furthermore, the (9,6) masers show velocity offsets with
respect to their systemic velocities. This indicates that the (9,6) masers are
located at the base of outflows, similar to the H2O masers. This is supported
by VLBI observations that show that (9,6) masers tend to be closely associated
with H2O masers (Pratap et al., 1991). The observed time variability in
G34.26$+$0.15 and W51-IRS2 can also be attributed to episodic molecular
outflows. This indicates that collisional pumping could be the driver of the
(9,6) maser. On the other hand, collisional pumping has been successfully used
to explain the NH3 (3,3) maser (Walmsley & Ungerechts, 1983; Flower et al.,
1990; Mangum & Wootten, 1994). Collisions tend to pump from the $K$=0 level to
the $K$=3 level with parity changes, that is, the upper level of the (3,3)
metastable transition will be overpopulated. NH3 (9,6) arises from the ortho
species, so a similar mechanism might also occur in the case of the (9,6)
transition. Further measurements of collisional rates of ammonia will allow us
to test this scenario.

##  5 Summary

We report the discovery of NH3 (9,6) masers in two HMSFRs, Cep A and
G34.26$+$0.15. The narrow line width of the emission features ($\Delta
V_{1/2}\leq$2.0 km s-1) and their high brightness temperatures ($>400$ K)
indicate the maser nature of the lines. The intensity of the (9,6) maser in
G34.26$+$0.15 is decreasing with time, while toward Cep A the maser is stable
based on 20 months of monitoring at Effelsberg. Linearly interpolating the
integrated intensities obtained at Effelsberg as a function of time, the JVLA
measurements show that there is no missing flux density on scales on the order
of 1.2 arcsec (4 $\times 10^{-3}$ and 2 $\times 10^{-2}$ pc) to the total
single-dish flux. The JVLA-detected emission indicates that the NH3 (9,6)
maser in Cep A originates from a sub-arcsecond-sized region slightly
($0\aas@@fstack{\prime\prime}28\pm 0\aas@@fstack{\prime\prime}10$) to the west
of the peak position of the 1.36 cm continuum object, HW2. In G34.26$+$0.15,
three NH3 (9,6) maser spots are observed: one is close to the head of the
cometary UC H II region C, and the other two are emitted from a compact region
to the west of the HC H II region A. We suggest that the (9,6) masers may be
connected to outflowing gas. Higher angular resolution JVLA and VLBI
observations are planned to provide more accurate positions and constraints on
pumping scenarios.

###### Acknowledgements.

We would like to thank the anonymous referee for the useful comments that
improve the manuscript. Y.T.Y. is a member of the International Max Planck
Research School (IMPRS) for Astronomy and Astrophysics at the Universities of
Bonn and Cologne. Y.T.Y. would like to thank the China Scholarship Council
(CSC) for its support. We would like to thank the staff at the Effelsberg for
their help provided during the observations. We thank the staff of the JVLA,
especially Tony Perreault and Edward Starr, for their assistance with the
observations and data reduction. This research has made use of the NASA/IPAC
Infrared Science Archive, which is funded by the National Aeronautics and
Space Administration and operated by the California Institute of Technology.

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## Appendix A

Table 1: Summary of NH3 (9, 6) maser observations.

Source | Telescope | Beam | Epoch | Channel | $S_{\nu}$ | rms | $\int S_{\nu}dv$ | $V_{\rm LSR}$ | $\Delta V_{1/2}$
---|---|---|---|---|---|---|---|---|---
|  | size |  | spacing |  |  |  |  |
|  |  |  | (km s-1) | (Jy) | (mJy) | (Jy km s-1) | (km s-1)
Cep A | Effelsberg | 49$\arcsec$ | 2020, Jan. 04 | 0.62 | 0.67 | 3.41 | 1.19 $\pm$ 0.02 | -1.11 $\pm$ 0.02 | 1.67 $\pm$ 0.04
| Effelsberg | 49$\arcsec$ | 2021, Feb. 11 | 0.62 | 0.59 | 5.97 | 1.08 $\pm$ 0.02 | -0.74 $\pm$ 0.02 | 1.70 $\pm$ 0.04
| Effelsberg | 49$\arcsec$ | 2021, Feb. 15 | 0.62 | 0.65 | 10.98 | 1.11 $\pm$ 0.03 | -0.75 $\pm$ 0.02 | 1.60 $\pm$ 0.05
| JVLAaa$a$The JVLA spectrum toward Cep A is extracted from the Effelsberg-beam-sized region (FWHM 49$\arcsec$). | $1\aas@@fstack{\prime\prime}47\leavevmode\nobreak\ \times\leavevmode\nobreak\ 0\aas@@fstack{\prime\prime}99$ | 2021, Jul. 13 | 0.13 | 1.13 | 144 | 0.89 $\pm$ 0.09 | -0.86 $\pm$ 0.03 | 0.74 $\pm$ 0.12
| Effelsberg | 49$\arcsec$ | 2021, Aug. 11 | 0.07 | 0.98 | 13.36 | 0.49 $\pm$ 0.02 | -0.90 $\pm$ 0.01 | 0.47 $\pm$ 0.01
|  |  |  |  | 0.35 |  | 0.26 $\pm$ 0.02 | -0.28 $\pm$ 0.02 | 0.69 $\pm$ 0.05
| Effelsberg | 49$\arcsec$ | 2021, Aug. 12 | 0.07 | 0.98 | 13.35 | 0.50 $\pm$ 0.01 | -0.89 $\pm$ 0.07 | 0.48 $\pm$ 0.07
|  |  |  |  | 0.35 |  | 0.20 $\pm$ 0.01 | -0.29 $\pm$ 0.07 | 0.54 $\pm$ 0.07
|  |  |  |  | 0.06 |  | 0.07 $\pm$ 0.01 | 0.51 $\pm$ 0.07 | 1.09 $\pm$ 0.07
|  |  |  |  | 0.02 |  | 0.02 $\pm$ 0.01 | 2.15 $\pm$ 0.07 | 0.80 $\pm$ 0.07
|  |  |  |  | 0.07 |  | 0.06 $\pm$ 0.01 | 2.89 $\pm$ 0.07 | 0.92 $\pm$ 0.07
G34.26+0.15 | Effelsberg | 49$\arcsec$ | 2020, Jan. 03 | 0.62 | 0.30 | 1.26 | 0.65 $\pm$ 0.03 | 62.50 $\pm$ 0.05 | 2.05 $\pm$ 0.13
| Effelsberg | 49$\arcsec$ | 2021, Feb. 11 | 0.62 | 0.24 | 2.42 | 0.40 $\pm$ 0.02 | 55.76 $\pm$ 0.04 | 1.60 $\pm$ 0.12
| Effelsberg | 49$\arcsec$ | 2021, Feb. 15 | 0.62 | 0.20 | 4.86 | 0.38 $\pm$ 0.02 | 55.71 $\pm$ 0.05 | 1.80 $\pm$ 0.14
| JVLAbb$b$For G34.26$+$0.15, the JVLA beam samples the NH3 (9,6) spectrum over a region of radius 3$\aas@@fstack{\prime\prime}$5, which contains all detected NH3 (9,6) emissions. | $1\aas@@fstack{\prime\prime}33\leavevmode\nobreak\ \times\leavevmode\nobreak\ 1\aas@@fstack{\prime\prime}06$ | 2021, Jul. 13 | 0.13 | 0.23 | 37.1 | 0.09 $\pm$ 0.02 | 54.41 $\pm$ 0.03 | 0.38 $\pm$ 0.09
|  |  |  |  | 0.22 |  | 0.22 $\pm$ 0.02 | 55.82 $\pm$ 0.05 | 0.95 $\pm$ 0.12
|  |  |  |  | 0.15 |  | 0.06 $\pm$ 0.01 | 57.21 $\pm$ 0.04 | 0.35 $\pm$ 0.08
| Effelsberg | 49$\arcsec$ | 2021, Aug. 11 | 0.07 | 0.08 | 13.92 | 0.06 $\pm$ 0.007 | 54.10 $\pm$ 0.05 | 0.68 $\pm$ 0.12
|  |  |  |  | 0.07 |  | 0.02 $\pm$ 0.006 | 54.82 $\pm$ 0.03 | 0.31 $\pm$ 0.09
|  |  |  |  | 0.12 |  | 0.10 $\pm$ 0.006 | 55.85 $\pm$ 0.02 | 0.75 $\pm$ 0.06
| Effelsberg | 49$\arcsec$ | 2021, Aug. 12 | 0.07 | 0.16 | 27.40 | 0.09 $\pm$ 0.008 | 55.83 $\pm$ 0.02 | 0.56 $\pm$ 0.05

666 The spectral parameters are obtained from Gaussian fitting.

Table 2: 1.36 cm JVLA flux densities of individual continuum sources. Source | R.A. | Dec. | Size | P.A. | $S_{\nu}$
---|---|---|---|---|---
|  | ($h\quad m\quad s$) | ($\degr\quad\arcmin\quad\arcsec$) | (arcsec) | (deg) | (mJy)
Cep A | HW2 | 22 56 17.972 $\pm$ 0.003 |  $+$62 01 49.587 $\pm$ 0.015 | (0.45 $\pm$ 0.19) $\times$ (0.22 $\pm$ 0.10) | 50.0 | 20.2 $\pm$ 1.4
| HW3a | 22 56 17.420 $\pm$ 0.022 |  $+$62 01 44.576 $\pm$ 0.076 | (2.35 $\pm$ 0.45) $\times$ (0.55 $\pm$ 0.14) | 66.6 | 4.75 $\pm$ 0.74
| HW3b | 22 56 17.578 $\pm$ 0.009 |  $+$62 01 45.041 $\pm$ 0.043 | (1.43 $\pm$ 0.24) $\times$ (0.45 $\pm$ 0.10) | 59.9 | 3.19 $\pm$ 0.36
| HW3c | 22 56 17.956 $\pm$ 0.016 |  $+$62 01 46.224 $\pm$ 0.038 | (1.44 $\pm$ 0.37) $\times$ (0.36 $\pm$ 0.19) | 86.0 | 9.90 $\pm$ 1.7
| HW3d | 22 56 18.195 $\pm$ 0.005 |  $+$62 01 46.325 $\pm$ 0.014 | (1.26 $\pm$ 0.12) $\times$ (0.30 $\pm$ 0.19) | 102.5 | 13.75 $\pm$ 0.92
| HW9 | 22 56 18.626 $\pm$ 0.014 |  $+$62 01 47.851 $\pm$ 0.137 | (1.53 $\pm$ 0.51) $\times$ (0.29 $\pm$ 0.30) | 28.0 | 3.26 $\pm$ 0.78
G34.26+0.15 | A | 18 53 18.774 $\pm$ 0.005 |  $+$01 14 56.208 $\pm$ 0.125 | (0.66 $\pm$ 0.49) $\times$ (0.50 $\pm$ 0.33) | 10.0 | 94 $\pm$ 33
| B | 18 53 18.649 $\pm$ 0.005 |  $+$01 15 00.071 $\pm$ 0.180 | (2.31 $\pm$ 0.49) $\times$ (0.85 $\pm$ 0.21) | 17.4 | 597 $\pm$ 110
| C | 18 53 18.560 $\pm$ 0.004 |  $+$01 14 58.201 $\pm$ 0.112 | (2.03 $\pm$ 0.30) $\times$ (1.34 $\pm$ 0.20) | 178.0 | 5070 $\pm$ 660
Table 3: NH3 (9,6) maser positions derived from the JVLA observations. Source | R.A. | Dec. | $S_{\nu}$ | $T_{\rm MB}$ | $V_{\rm LSR}$ | $\Delta V_{1/2}$
---|---|---|---|---|---|---
|  | ($h\quad m\quad s$) | ($\degr\quad\arcmin\quad\arcsec$) | (mJy beam-1) | (K) | (km s-1)
Cep A | M | 22 56 17.933 $\pm$ 0.002 |  $+$62 01 49.608 $\pm$ 0.011 | 985.2 | 2464.8 | -0.88 $\pm$ 0.01 | 0.51 $\pm$ 0.02
|  |  |  | 343.2 | 829.5 | -0.24 $\pm$ 0.03 | 0.63 $\pm$ 0.05
G34.26+0.15 | M1 | 18 53 18.569 $\pm$ 0.007 |  $+$01 14 57.997 $\pm$ 0.056 | 37.1 | 94.5 | 56.82 $\pm$ 0.06 | 0.68 $\pm$ 0.14
| M2 | 18 53 18.696 $\pm$ 0.002 |  $+$01 14 55.807 $\pm$ 0.034 | 48.4 | 122.4 | 53.77 $\pm$ 0.05 | 0.35 $\pm$ 0.08
|  |  |  | 57.8 | 146.2 | 54.35 $\pm$ 0.07 | 0.83 $\pm$ 0.14
|  |  |  | 180.8 | 457.6 | 55.83 $\pm$ 0.01 | 0.59 $\pm$ 0.03
| M3 | 18 53 18.667 $\pm$ 0.005 |  $+$01 14 55.348 $\pm$ 0.066 | 78.1 | 197.2 | 54.22 $\pm$ 0.04 | 0.94 $\pm$ 0.08
|  |  |  | 73.7 | 186.3 | 55.78 $\pm$ 0.04 | 0.79 $\pm$ 0.08
Figure 5: Cepheus A. The grey shaded areas mark the 1.36 cm JVLA continuum map
of Cep A. The reference position is $\alpha_{\rm J2000}$ =
22h56m17$\aas@@fstack{s}$972, and $\delta_{\rm J2000}$ =
62$\degr$01$\arcmin$49$\aas@@fstack{\prime\prime}$587, the peak position of
the continuum map, is marked by a red cross. Slightly to the west of the cross
is the white ellipse denoting the position of the NH3 (9,6) emission with a
purple star at its center. The red contours show the NOrthern Extended
Millimeter Array (NOEMA) 1.37 mm continuum, taken from Beuther et al. (2018).
Contour levels are -5, 5, 10, 20, 40, 80, 100, 150, and 200 $\times$ 2.43 mJy
beam-1. OH (Bartkiewicz et al. 2005), H2O (Sobolev et al. 2018), and CH3OH
(Sanna et al. 2017) masers are presented as diamonds, circles, and squares,
respectively. The color bar on the right-hand side indicates the velocity
range ($V_{\rm LSR}$) of maser spots. Figure 6: 1.36 cm JVLA continuum map of
G34.26$+$0.15 presented as gray shaded areas. The reference position is
$\alpha_{\rm J2000}$ = 18h53m18$\aas@@fstack{s}$560, and $\delta_{\rm J2000}$
= 01$\degr$14$\arcmin$58$\aas@@fstack{\prime\prime}$201, the peak position, is
marked by a red cross. The red ellipses show the positions of NH3 (9,6)
emission with stars at their center (i.e., M1, M2, and M3). The blue contours
show the Berkeley-Illinois-Maryland Association (BIMA) array 2.8 mm continuum,
taken from Mookerjea et al. (2007). Contour levels are -3, 3, 10, 20, 30, 40,
50, 70, 90, 100, 120, and 140 $\times$ 20 mJy beam-1. OH (Zheng et al. 2000),
H2O (Imai et al. 2011), and CH3OH (Bartkiewicz et al. 2016) masers are
presented as diamonds, circles, and squares, respectively. The color bar
indicates the velocity range ($V_{\rm LSR}$) of maser spots.