J/A+A/666/L15 Non-metastable ammonia masers in Sgr B2 (Yan+, 2022)
Discovery of non-metastable ammonia masers in Sagittarius B2.
Yan Y.T., Henkel C., Menten K.M., Gong Y., Nguyen H., Ott J., Ginsburg A.,
Wilson T.L., Brunthaler A., Belloche A., Zhang J.S., Budaiev N., Jeff D.
<Astron. Astrophys., 666, L15 (2022)>
=2022A&A...666L..15Y 2022A&A...666L..15Y (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Radio lines ; Masers
Keywords: radio lines: ISM
Abstract:
We report the discovery of widespread maser emission in non-metastable
inversion transitions of NH3 toward various parts of the Sagittarius
B2 molecular cloud and star-forming region complex. We detect masers
in the J, K = (6, 3), (7,4), (8,5), (9,6), and (10,7) transitions
toward Sgr B2(M) and Sgr B2(N), an NH3 (6,3) maser in Sgr B2(NS),
and NH3 (7,4), (9,6), and (10,7) masers in Sgr B2(S). With the high
angular resolution data of the Karl G. Jansky Very Large Array (JVLA)
in the A-configuration, we identify 18 maser spots. Nine maser spots
arise from Sgr B2(N), one from Sgr B2(NS), five from Sgr B2(M), and
three in Sgr B2(S). Compared to our Effelsberg single-dish data, the
JVLA data indicate no missing flux. The detected maser spots are not
resolved by our JVLA observations. Lower limits to the brightness
temperature are >3000K and reach up to several 105K, manifesting
the lines' maser nature. In view of the masers' velocity differences
with respect to adjacent hot molecular cores and/or UCHII regions, it
is argued that all the measured ammonia maser lines may be associated
with shocks caused either by outflows or by the expansion of UCHII
regions. Overall, Sgr B2 is unique in that it allows us to measure
many NH3 masers simultaneously, which may be essential in order to
elucidate their thus far poorly understood origin and excitation.
Description:
1.6cm JVLA flux densities of individual continuum sources and NH3
maser positions in Sgr B2, derived from the JVLA observation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb5.dat 96 22 1.6cm JVLA flux densities of individual
continuum sources
tableb6.dat 88 34 NH3 maser positions in Sgr B2,
derived from the JVLA observations.
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Byte-by-byte Description of file: tableb5.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Source Source name
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 27 F6.3 s RAs Right ascension (J2000)
29- 33 F5.3 s e_RAs Right ascension error
35 A1 --- DE- Declination sign (J2000)
36- 37 I2 deg DEd Declination (J2000)
39- 40 I2 arcmin DEm Declination (J2000)
42- 47 F6.3 arcsec DEs Declination (J2000)
49- 53 F5.3 arcsec e_DEs Declination error
55 A1 --- l_Size1 [-] Limit flag on Size1
56- 60 F5.3 arcsec Size1 Deconvolved size
62- 66 F5.3 arcsec e_Size1 ? Deconvolved size error
68 A1 --- l_Size2 [-] Limit flag on Size2
69- 73 F5.3 arcsec Size2 Deconvolved size
75- 79 F5.3 arcsec e_Size2 ? Deconvolved size error
81- 85 F5.1 deg PA ? Position angle
87- 90 I4 mJy Snu 1.6cm JVLA flux density
92- 96 F5.1 mJy e_Snu 1.6cm JVLA flux density error
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Byte-by-byte Description of file: tableb6.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Trans Transition
8- 11 A4 --- Maser NH3 maser name
12- 13 A2 --- n_Maser Note on Maser (1)
15- 16 I2 h RAh Right ascension (J2000)
18- 19 I2 min RAm Right ascension (J2000)
21- 26 F6.3 s RAs Right ascension (J2000)
28- 32 F5.3 s e_RAs Right ascension error
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 46 F6.3 arcsec DEs Declination (J2000)
48- 52 F5.3 arcsec e_DEs Declination error
54- 58 F5.3 Jy/beam Snu JLVA 1.6bm flux
60- 65 F6.3 10+4K TMB Mean brigthness temperature
67- 71 F5.2 km/s VLSR LSR velocity
73- 77 F5.3 km/s e_VLSR LSR velocity error
79- 82 F4.2 km/s DeltaV1/2 Average value of the FWHM of the line
84- 88 F5.3 km/s e_DeltaV1/2 Average value of the FWHM of the line error
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Note (1): Notes as follows:
+ = These nine maser spots originate in Sgr B2(N)
x = 63C arises in Sgr B2(NS)
* = These five maser sources belong to Sgr B2(M)
** = These three maser spots originate in Sgr B2(S). The flux density
scale calibration accuracy is estimated to be within 15%.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Feb-2023