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J/A+A/604/A6     SgrB2 ALMA continuum and spectral index  (Sanchez-Monge+, 2017)

The physical and chemical structure of Sagittarius B2. II. Continuum millimeter emission of SgrB2(M) and SgrB2(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., Moeller T. <Astron. Astrophys. 604, A6 (2017)> =2017A&A...604A...6S (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio continuum ; YSOs Keywords: stars: formation - stars: massive - radio continuum: ISM - radio lines: ISM - ISM: individual objects: SgrB2(M) - ISM: individual objects: SgrB2(N) Abstract: The two hot molecular cores SgrB2(M) and SgrB2(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. We seek to characterize the physical and chemical structure of the two high-mass star-forming sites SgrB2(M) and SgrB2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000au. 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-arcsec, 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. We detect 27 continuum sources in SgrB2(M) and 20 sources in SgrB2(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 SgrB2(M) is distributed in many fragments, most of the mass in SgrB2(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, SgrB2(N) is chemically richer than SgrB2(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 SgrB2(N) and SgrB2(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 SgrB2 from 45pc down to 100au. This ALMA dataset, together with other ongoing observational projects in the range 5GHz to 200GHz, better constrain the 3D structure of SgrB2 and allow us to understand its physical and chemical structure. Description: ALMA 1.3mm (242GHz) continuum maps of the high-mass star-forming regions SgrB2(M) and SgrB2(N). The angular resolution of the images is 0.4-arcsec, and were obtained after combining different continuum images obtained from the ALMA spectral line survey in band 6 (from 211GHz to 275GHz). The different continuum images are used to produce the spectral index maps of both regions. Objects: ------------------------------------------------------- RA (2000) DE Designation(s) ------------------------------------------------------- 17 47 20.157 -28 23 04.53 SgrB2(M) = NAME Sgr B2(M) 17 47 19.887 -28 22 15.76 SgrB2(N) = NAME Sgr B2(N) ------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 135 4 List of fits images fits/* 0 4 Individual fits images
See also: J/ApJS/117/427 : Sgr B2 spectral survey (Nummelin+, 1998) J/ApJS/158/188 : Detection of glycolaldehyde toward Sgr B2 (Widicus+, 2005) J/A+A/482/179 : Interferometric study of SgrB2(N) (Belloche+, 2008) J/A+A/559/A47 : Sgr B2(N) and Sgr B2(M) IRAM 30m line survey (Belloche+, 2013) Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 22 I3 --- Nx Number of pixels along X-axis 24- 26 I3 --- Ny Number of pixels along Y-axis 28- 53 A26 --- Obs.Date Observation date *YYYY-MM-DDThh:mm:ss.ssssss) 55- 58 I4 Kibyte size Size of FITS file 60- 71 A12 --- FileName Name of FITS file, in subdirectory fits 73-135 A63 --- Title Title of the FITS file
Acknowledgements: Alvaro Sanchez-Monge, sanchez(at) References: Schmiedeke et al., Paper I 2016A&A...588A.143S
(End) Alvaro Sanchez-Monge [Cologne, Germany] Patricia Vannier [CDS] 27-Apr-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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