2017A&A...604A...6S


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.07CET09:45:12

2017A&A...604A...6S - Astronomy and Astrophysics, volume 604A, 6-6 (2017/8-1)

The physical and chemical structure of Sagittarius B2. II. Continuum millimeter emission of Sgr B2(M) and Sgr B2(N) with ALMA.

SANCHEZ-MONGE A., SCHILKE P., SCHMIEDEKE A., GINSBURG A., CESARONI R., LIS D.C., QIN S.-L., MUELLER H.S.P., BERGIN E., COMITO C. and MOLLER T.

Abstract (from CDS):

Context. The two hot molecular cores Sgr B2(M) and Sgr B2(N), which are located at the center of the giant molecular cloud complex Sagittarius B2, have been the targets of numerous spectral line surveys, revealing a rich and complex chemistry.
Aims. We seek to characterize the physical and chemical structure of the two high-mass star-forming sites Sgr B2(M) and Sgr B2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000au.
Methods. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to perform an unbiased spectral line survey of both regions in the ALMA band 6 with a frequency coverage from 211GHz to 275GHz. The achieved angular resolution is 0.4, which probes spatial scales of about 4000au, i.e., able to resolve different cores and fragments. In order to determine the continuum emission in these line-rich sources, we used a new statistical method, STATCONT, which has been applied successfully to this and other ALMA datasets and to synthetic observations.
Results. We detect 27 continuum sources in Sgr B2(M) and 20 sources in Sgr B2(N). We study the continuum emission variation across the ALMA band 6 (i.e., spectral index) and compare the ALMA 1.3mm continuum emission with previous SMA 345GHz and VLA 40GHz observations to study the nature of the sources detected. The brightest sources are dominated by (partially optically thick) dust emission, while there is an important degree of contamination from ionized gas free-free emission in weaker sources. While the total mass in Sgr B2(M) is distributed in many fragments, most of the mass in Sgr B2(N) arises from a single object, with filamentary-like structures converging toward the center. There seems to be a lack of low-mass dense cores in both regions. We determine H2 volume densities for the cores of about 107-109cm–3 (or 105-107M/pc3), i.e., one to two orders of magnitude higher than the stellar densities of super star clusters. We perform a statistical study of the chemical content of the identified sources. In general, Sgr B2(N) is chemically richer than Sgr B2(M). The chemically richest sources have about 100 lines per GHz and the fraction of luminosity contained in spectral lines at millimeter wavelengths with respect to the total luminosity is about 20%-40%. There seems to be a correlation between the chemical richness and the mass of the fragments, where more massive clumps are more chemically rich. Both Sgr B2(N) and Sgr B2(M) harbor a cluster of hot molecular cores. We compare the continuum images with predictions from a detailed 3D radiative transfer model that reproduces the structure of Sgr B2 from 45 pc down to 100au.
Conclusions. This ALMA dataset, together with other ongoing observational projects in the range 5GHz to 200GHz, better constrain the 3D structure of Sgr B2 and allow us to understand its physical and chemical structure.

Abstract Copyright: © ESO, 2017

Journal keyword(s): stars: formation - stars: massive - radio continuum: ISM - radio lines: ISM - ISM: individual objects: SgrB2(M) - ISM: individual objects: SgrB2(N) - ISM: individual objects: SgrB2(N)

VizieR on-line data: <Available at CDS (J/A+A/604/A6): list.dat fits/*>

Nomenclature: Tables 1-2: [SSS2017b] AANN (Nos AN01-AN20, AM01-AM27).

Status in Simbad:  being processed

Simbad objects: 20

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Number of rows : 20

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 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 1948 1
2 QSO B1730-130 QSO 17 33 02.70578476 -13 04 49.5481484   18 18.5 18.78   ~ 958 1
3 QSO J1744-3116 QSO 17 44 23.57824 -31 16 36.2943           ~ 108 1
4 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11077 0
5 [QSR2011] Sgr B2(N)-SMA2 cor 17 47 19.885 -28 22 13.29           ~ 35 0
6 [BMG2016] Sgr B2(N1) cor 17 47 19.889 -28 22 18.22           ~ 20 0
7 [QSR2011] Sgr B2(M)-SMA7 cor 17 47 20.110 -28 23 06.18           ~ 3 0
8 [QSR2011] Sgr B2(M)-SMA6 cor 17 47 20.171 -28 23 05.91           ~ 3 0
9 NAME Sgr B2 (North) Rad 17 47 20.2 -28 22 21           ~ 500 1
10 [QSR2011] Sgr B2(M)-SMA8 cor 17 47 20.216 -28 23 06.48           ~ 3 0
11 [QSR2011] Sgr B2(M)-SMA9 cor 17 47 20.238 -28 23 06.87           ~ 3 0
12 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1860 1
13 NAME Large Molecule Heimat MoC 17 47 20.4943 -28 22 11.656           ~ 109 0
14 NAME Sgr B2 Main Rad 17 47 20.5 -28 23 06           ~ 326 1
15 NVSS J175233-295645 Rad 17 52 33.10692495 -29 56 44.8974049           ~ 11 0
16 NAME Dragon Nebula DNe 18 42 50.6 -04 03 30           ~ 100 0
17 GAL 029.96-00.02 Y*O 18 46 03.7 -02 39 21           ~ 327 1
18 IRAS 18449-0115 cor 18 47 34.4947 -01 12 40.269           ~ 295 0
19 [WWB83] G033.91+0.11 HII 18 52 50.4 +00 55 29           ~ 86 1
20 W 51e2 Rad 19 23 43.90 +14 30 34.8           ~ 177 0

    Equat.    Gal    SGal    Ecl

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2019.12.07-09:45:12

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