J/ApJ/916/69 272-375GHz obs. toward SgrA*'s circumnuclear disk (James+, 2021)
Revealing the physical conditions around Sgr A* using Bayesian inference.
I. Observations and radiative transfer.
James T.A., Viti S., Yusef-Zadeh F., Royster M., Wardle M.
<Astrophys. J., 916, 69 (2021)>
=2021ApJ...916...69J 2021ApJ...916...69J
ADC_Keywords: Millimetric/submm sources; Interstellar medium; Radial velocities
Keywords: Interstellar medium ; Molecular clouds ; Star formation ;
Astrochemistry ; Radiative transfer ; Bayesian statistics ;
Observational astronomy ; Spectral line identification
Abstract:
We report subarcsecond Atacama Large Millimeter/submillimeter Array
(ALMA) observations between 272 and 375GHz toward Sgr A*'s
circumnuclear disk (CND). Our data comprise eight individual
pointings, with significant SiO (87-76) and SO (7-6) emission
detected toward 98 positions within these pointings. Additionally, we
identify H2CS (91,9-81,8), OCS (25-24), and CH3OH (21,1-20,2)
toward a smaller subset of positions. By using the observed peak line
flux density, together with a Bayesian inference technique informed by
radiative transfer models, we systematically recover the physical gas
conditions toward each of these positions. We estimate that the bulk
of the surveyed gas has temperature Tkin<500K and density
nH≲106cm-3, consistent with previous studies of similar
positions as traced by HCN clumps. However, we identify an
uncharacteristically hot (Tkin∼600K) and dense (nH∼106cm-3)
source in the Northeastern Arm. This position is found to be
approximately consistent with a gravitationally bound region dominated
by turbulence. We also identify a nearby cold (Tkin∼60K) and
extremely dense (nH∼107cm-3) position that is again potentially
bound and dominated by turbulence. We also determine that the total
gas mass contained within the CND is MCND≲4x104M☉.
Furthermore, we qualitatively note that the observed chemical
enrichment across large scales within the CND is consistent with bulk
grain processing, though multiple desorption mechanisms are plausibly
responsible. Further chemical modeling is required to identify the
physical origin of the grain processing, as well as the localized H2CS
and OCS emission.
Description:
ALMA Cycle 2 Band 7 (272-375GHz) observations (Project Code
2013.1.01242.S) that target various SiO transitions toward the SgrA*'s
circumnuclear disk (CND) are utilized for this investigation.
Eight pointings with the 12m array were obtained on 2015 June 8.
See Section 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 99 218 *Summary of observations
table4.dat 75 96 The points of highest posterior density of the
physical conditions toward each observational source
fig9/* . 93 Individual spectra for each position in which at
least one line was identified in JPEG format
(Figure 9 data behind the figure)
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Note on table3.dat : Table 3 shows the spectral line fitting quantities,
including molecule and transition as well the line's flux and line
width, for the spectra in Appendix A (see Fig 9 data behind the figure).
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See also:
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+, 2006)
J/ApJ/764/L19 : Methanol emission from the Gal. Center (Yusef-Zadeh+, 2013)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Source designation
6- 7 A2 --- m_ID [c1 ] Component number on ID
9- 10 I2 h RAh Hour of right ascension (J2000)
12- 13 I2 min RAm Minute of right ascension (J2000)
15- 19 F5.2 s RAs Second of right ascension (J2000)
21 A1 --- DE- Sign of declination (J2000)
22- 23 I2 deg DEd Degree of declination (J2000)
25- 26 I2 arcmin DEm Arcminute of declination (J2000)
28- 32 F5.2 arcsec DEs Arcsecond of declination (J2000)
34- 38 F5.2 --- Extent [1/89.4] Extent in beam sizes
40- 59 A20 --- Line Emission line detected
61- 65 F5.2 mJy/beam Flux [1.7/58.6] Peak Line flux density
67- 70 F4.2 mJy/beam e_Flux [0.1/9] Flux uncertainty
72- 79 F8.4 km/s Vlsr [-95.2/110] Local Standard of Rest velocity
81- 87 F7.3 km/s DelV [-15/36.6] Line width
89- 93 F5.2 --- SiO/Si [0.2/13.5]? Ratio of SiO to SO flux densities
95- 99 F5.2 --- e_SiO/Si [-0.01/9.7]? SiO/Si uncertainty
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Source designation
6- 7 A2 --- m_ID [c1/c2 ] Component number on ID
9- 11 I3 K Tkin [63/917]? Gas temperature
13- 15 I3 K e_Tkin [0/574]? Lower uncertainty on Tkin
17- 19 I3 K E_Tkin [22/509]? Upper uncertainty on Tkin
21- 24 F4.2 [cm-3] lognH [5.43/7]? Log of hydrogen density number
26- 29 F4.2 [cm-3] e_lognH [0.14/2]? Lower uncertainty on lognH
31- 34 F4.2 [cm-3] E_lognH [0/1.33]? Upper uncertainty on lognH
36- 41 F6.3 [cm-2] logNSiO [12.8/14.3] Log of SiO column density
43- 47 F5.3 [cm-2] e_logNSiO [0.05/1.01] Lower uncertainty on logNSiO
49- 53 F5.3 [cm-2] E_logNSiO [0.058/0.9] Upper uncertainty on logNSiO
55- 60 F6.3 [cm-2] logNSO [14/15.11]? Log of SO column density
62- 66 F5.3 [cm-2] e_logNSO [0.04/0.4]? Lower uncertainty on logNSO
68- 72 F5.3 [cm-2] E_logNSO [0.05/0.7]? Upper uncertainty on logNSO
74- 75 I2 --- Fig ? Figure set number (in Figure 9);
column added by CDS
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 29-Dec-2022