2011A&A...526A..54A


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.12CET15:40:24

2011A&A...526A..54A - Astronomy and Astrophysics, volume 526A, 54-54 (2011/2-1)

Mapping photodissociation and shocks in the vicinity of Sagittarius A*.

AMO-BALADRON M.A., MARTIN-PINTADO J. and MARTIN S.

Abstract (from CDS):

We study the chemistry in the harsh environments of galactic nuclei using the nearest one, the Galactic center (GC). We have obtained maps of the molecular emission within the central five arcminutes (12pc) of the GC in selected molecular tracers: SiO(2-1), HNCO(50,5-40,4), and the J=1-> 0 transition of H13CO+, HN13C, and C18O at an angular resolution of 30'' (1.2pc). The mapped region includes the circumnuclear disk (CND) and the two surrounding giant molecular clouds (GMCs) of the Sgr A complex, known as the 20 and 50km/s molecular clouds. Additionally, we simultaneously observed the J=2->1 and J=3->2 transitions of SiO toward selected positions to estimate the physical conditions of the molecular gas using the large velocity gradient approximation. The SiO(2-1) emission shows all the molecular features identified in previous studies, covering the same velocity range as the H13CO+(1-0) emission, which also presents a similar distribution. In contrast, HNCO(5-4) emission appears in a narrow velocity range mostly concentrated in the 20 and 50km/s GMCs. A similar trend follows the HN13C(1-0) emission. The HNCO column densities and fractional abundances present the highest contrast, with difference factors of ≥60 and 28, respectively. Their highest values are found toward the cores of the GMCs, whereas the lowest ones are measured at the CND. SiO abundances do not follow this trend, with high values found toward the CND, as well as the GMCs. By comparing our abundances with those of prototypical Galactic sources we conclude that HNCO, similar to SiO, is ejected from grain mantles into gas-phase by nondissociative C-shocks. This results in the high abundances measured toward the CND and the GMCs. However, the strong UV radiation from the Central cluster utterly photodissociates HNCO as we get closer to the center, whereas SiO seems to be more resistant against UV-photons or it is produced more efficiently by the strong shocks in the CND. This UV field could be also responsible for the trend found in the HN13C abundance. We discuss the possible connections between the molecular gas at the CND and the GMCs using the HNCO/SiO, SiO/CS, and HNCO/CS intensity ratios as probes of distance to the Central cluster. In particular, the HNCO/SiO intensity ratio is proved to be an excellent tool for evaluating the distance to the center of the different gas components.

Abstract Copyright:

Journal keyword(s): astrochemistry - ISM: clouds - ISM: molecules - Galaxy: abundances - Galaxy: nucleus - Galaxy: center

Simbad objects: 25

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Number of rows : 25

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 2861 2
2 IC 342 SBG 03 46 48.514 +68 05 45.98   10.5       ~ 1362 1
3 [DRG92] A Cld 03 46 48.55 +68 05 43.6           ~ 13 0
4 [DRG92] D Cld 03 46 48.94 +68 05 56.8           ~ 9 0
5 [DRG92] D' Cld 03 46 49.8 +68 05 59           ~ 2 0
6 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1327 0
7 NAME OMC-1 MoC 05 35 14 -05 22.4           ~ 991 2
8 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 1944 1
9 NAME Orion Core ? 05 35 14.5 -05 22 30           ~ 171 0
10 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 690 0
11 IC 443 SNR 06 18 02.7 +22 39 36           ~ 1073 1
12 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5220 6
13 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1231 2
14 NAME Sgr A Region reg 17 45 12 -28 48.3           ~ 910 0
15 GCM -0.13 -0.08 MoC 17 45 25.2 -29 05 30           ~ 103 1
16 NAME Sgr A West HII 17 45 39.4 -29 00 24           ~ 345 0
17 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 3277 3
18 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11035 0
19 NAME Sgr A East Rad 17 45 41 -29 00.8           ~ 433 2
20 SNR G359.9-00.9 SNR 17 45.8 -29 03           ~ 25 1
21 GCM -0.02 -0.07 MoC 17 45 50.4 -28 59 06           ~ 136 0
22 NAME Sgr B2 (North) Rad 17 47 20.2 -28 22 21           ~ 497 1
23 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1855 1
24 SH 2-140 OpC 22 19 07.8 +63 17 07           ~ 628 2
25 IRAS 22176+6303 SFR 22 19 17.978 +63 18 52.92           ~ 587 0

    Equat.    Gal    SGal    Ecl

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2019.11.12-15:40:24

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