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J/A+A/610/A10       Sgr B2 los molecular absorption line spectra (Corby+, 2018)

The molecular chemistry of diffuse and translucent clouds in the line-of-sight to Sgr B2: Absorption by simple organic and inorganic molecules in the GBT PRIMOS survey. Corby J.F., McGuire B.A., Herbst E., Remijan A.J. <Astron. Astrophys. 610, A10 (2018)> =2018A&A...610A..10C (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; Spectroscopy Keywords: astrochemistry - radio lines: ISM - ISM: abundances - molecular processes - ISM: structure - Galaxy: center Abstract: The 1-50 GHz PRebiotic Interstellar MOlecular Survey (PRIMOS) contains >50 molecular absorption lines observed in clouds located in the line-of-sight to Sgr B2(N). The line-of- sight material is associated with diffuse and translucent clouds located in the Galactic Center, Bar, and spiral arms in the disk. We measure the column densities and estimate abundances, relative to H2, of 11 molecules and additional isotopologues observed in this material. We use absorption by optically thin transitions of c-C3H2 to estimate the molecular hydrogen columns, and argue that this method is preferable to more commonly used methods. We discuss the kinematic structure and abundance patterns of small molecules including the sulfur-bearing species CS, SO, CCS, H2CS, and HCS+; oxygen-bearing molecules OH, SiO, and H2CO; and simple hydrocarbon molecules c-C3H2, l-C3H, and l-C3H+. Finally, we discuss the implications of the observed chemistry for the structure of the gas and dust in the ISM. Highlighted results include the following. First, whereas gas in the disk has a molecular hydrogen fraction of 0.65, clouds on the outer edge of the Galactic Bar and in or near the Galactic Center have molecular fractions of 0.85 and >0.9, respectively. Second, we observe trends in isotope ratios with Galactocentric distance; while carbon and silicon show enhancement of the rare isotopes at low Galactocentric distances, sulfur exhibits no trend with Galactocentric distance. We also determine that the ratio of c-C3H2/c-H13CCCH provides a good estimate of the 12C/13C ratio, whereas H2CO/H2(13C)O exhibits fractionation. Third, we report the presence of l-C3H+ in diffuse clouds for the first time. Finally, we suggest that CS has an enhanced abundance within higher density clumps of material in the disk, and therefore may be diagnostic of cloud conditions. If this holds, the diffuse clouds in the Galactic disk contain multiple embedded hyperdensities in a clumpy structure, and the density profile is not a simple function of AV. Description: Spectra covering transitions of c-C3H2, c-H13CCCH, CS, C34S, SO, CCS, H2CS, HCS+, OH, SiO, 29SiO, H2CO, H2(13C)O, l-C3H, and l-C3H+ with line-of-sight absorption observed in the 1-50 GHz data from the PRebiotic Interstellar MOlecular Survey (PRIMOS) taken with the Robert C. Byrd Green Bank Telescope (GBT). Data were observed between 2001 and 2014, with the majority of the data obtained in 2007 in GBT Key Science project ID GBT07A-051. Spectra have been baseline-subtracted using best fit polynomials as described in the paper, and normalized by the continuum, so that the y-axis represents (T/TC-1). Data are provided in the FITS format; each FITS file contains all lines of a single molecule that are observed to have foreground absorption. Please refer to Table 1 of the paper to obtain molecular transition rest frequencies, energies, GBT beam sizes, and transition quantum numbers. Objects: ------------------------------------------------- RA (2000) DE Designation(s) ------------------------------------------------- 17 47 20.4 -28 22 12 Sgr B2 = NAME SGR B2 ------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file spectra.dat 110 26 list of spectra fits/* 0 15 Individual fits files
See also: J/MNRAS/452/3969 : ATCA Survey of Sagittarius B2 at 7mm (Corby+, 2015) J/A+A/559/A47 : Sgr B2(N) and Sgr B2(M) IRAM 30m line survey (Belloche+, 2013) Byte-by-byte Description of file: spectra.dat
Bytes Format Units Label Explanations
1- 8 F8.4 deg RAdeg Right Ascension of center (J2000) 10- 17 F8.4 deg DEdeg Declination of center (J2000) 19 I1 --- Nrec [1/4] Number of records in the fits file 21- 24 I4 --- Nline Number of lines 26- 43 A18 --- FileName Name of FITS file, in subdirectory fits 45-110 A66 --- Title Descriptor of file contents
Acknowledgements: Joanna Corby, jfc2113(at)gmail.com Anthony Remijan, aremijan(at)nrao.edu National Radio Astronomy Observatory Funding through University of Virginia, Eric Herbst References: Thiel et al., 2017A&A...605L...6T, Complex organic molecules in diffuse clouds along the line of sight to Sagittarius B2.
(End) Patricia Vannier [CDS] 15-Dec-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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