2022A&A...666A..31M


Query : 2022A&A...666A..31M

2022A&A...666A..31M - Astronomy and Astrophysics, volume 666A, 31 (2022/10-1)

The physical and chemical structure of Sagittarius B2 VI. UCHii regions in Sgr B2.

MENG F., SANCHEZ-MONGE A., SCHILKE P., GINSBURG A., DEPREE C., BUDAIEV N., JEFF D., SCHMIEDEKE A., SCHWORER A., VEENA V.S. and MOLLER T.

Abstract (from CDS):


Context. The giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most massive region with ongoing high-mass star formation in the Galaxy. Two ultra-compact HII (UCHII ) regions were identified in SgrB2's central hot cores, SgrB2(M) and SgrB2(N).
Aims. Our aim is to characterize the properties of the HII regions in the entire SgrB2 cloud. Comparing the HII regions and the dust cores, we aim to depict the evolutionary stages of different parts of SgrB2.
Methods. We use the Very Large Array in its A, CnB, and D configurations, and in the frequency band C (∼6GHz) to observe the whole SgrB2 complex. Using ancillary VLA data at 22.4 GHz and ALMA data at 96 GHz, we calculated the physical parameters of the UCHII regions and their dense gas environment.
Results. We identify 54 UCHII regions in the 6 GHz image, 39 of which are also detected at 22.4 GHz. Eight of the 54 UCHII regions are newly discovered. The UCHII regions have radii between 0.006 pc and 0.04 pc, and have emission measure between 106 pc cm6 and 109 pc cm6. The UCHII regions are ionized by stars of types from B0.5 to O6. We found a typical gas density of ∼106-109 cm3 around the UCHII regions. The pressure of the UCHII regions and the dense gas surrounding them are comparable. The expansion timescale of these UCHII regions is determined to be ∼104-105 yr. The percentage of the dust cores that are associated with HII regions are 33%, 73%, 4%, and 1% for SgrB2(N), SgrB2(M), SgrB2(S), and SgrB2(DS), respectively. Two-thirds of the dust cores in SgrB2(DS) are associated with outflows.
Conclusions. The electron densities of the UCHII regions we identified are in agreement with that of typical UCHII regions, while the radii are smaller than those of the typical UCHII regions. The dust cores in SgrB2(M) are more evolved than in SgrB2(N). The dust cores in SgrB2(DS) are younger than in SgrB2(M) or SgrB2(N).

Abstract Copyright: © F. Meng et al. 2022

Journal keyword(s): stars: formation - stars: massive - radio continuum: ISM - radio lines: ISM - ISM: individual objects: Sgr B2 - ISM: clouds

VizieR on-line data: <Available at CDS (J/A+A/666/A31): tableb1.dat tableb2.dat list.dat fits/*>

Status at CDS : Examining the need for a new acronym. // All or part of tables of objects will be ingested in SIMBAD with priority 1.

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4351 2
2 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
3 NAME Sgr B1 MoC 17 47 02.0 -28 31 57           ~ 165 0
4 NAME Sgr B2 (North) Rad 17 47 20.2 -28 22 21           ~ 675 1
5 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 2271 1
6 NAME Sgr B2 (South) HII 17 47 20.430 -28 23 45.06           ~ 100 0
7 NAME Sgr B2 Main Rad 17 47 20.5 -28 23 06           ~ 408 1
8 QSO J1820-2528 QSO 18 20 57.84869964 -25 28 12.5840414   18.56       ~ 105 0
9 W 51 SNR 19 23 50 +14 06.0           ~ 1278 1

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