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J/A+A/600/A2        Hydrogen in diffuse molecular clouds         (Winkel+, 2017)

Hydrogen in diffuse molecular clouds in the Milky Way. Atomic column densities and molecular fraction along prominent lines of sight. Winkel B., Wiesemeyer H., Menten K.M., Sato M., Brunthaler A., Wyrowski F., Neufeld D., Gerin M., Indriolo N. <Astron. Astrophys. 600, A2 (2017)> =2017A&A...600A...2W (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way; H I data ; Interstellar medium ; Spectroscopy Keywords: astrochemistry - ISM: abundances - ISM: molecules Abstract: Recent sub-millimeter and far-infrared wavelength observations of absorption in the rotational ground state lines of various simple molecules against distant Galactic continuum sources have opened the possibility to study the chemistry of diffuse molecular clouds Milky Way-wide. In order to calculate abundances the column densities of molecular and atomic hydrogen, HI, must be known. We aim at determining the atomic hydrogen column densities for diffuse clouds located on the sight lines toward a sample of prominent high mass star forming regions that were intensely studied with the HIFI instrument onboard Herschel. Based on Jansky Very Large Array data, we employ the 21-cm HI absorption-line technique to construct profiles of the HI opacity versus radial velocity toward our target sources. These profiles are combined with lower resolution archival data of extended HI emission to calculate the HI column densities of the individual clouds along the sight lines. We employ Bayesian inference to estimate the uncertainties of the derived quantities. Our study delivers reliable estimates of the atomic hydrogen column density for a large number of diffuse molecular clouds at various Galactocentric distances. Together with column densities of molecular hydrogen derived from its surrogates observed with HIFI, the measurements can be used to characterize the clouds and, e.g., investigate the dependence of their chemistry on the molecular fraction. Description: To study the Hydrogen in diffuse molecular clouds in the Milky Way, eight sources were observed with the Jansky Very Large Array in spectral line mode at 21-cm. The targets have bright continuum emission and were used as background sources for HI absorption spectroscopy. The brightest positions in the background continuum images were used to define several sight lines per source and to extract associated HI absorption spectra. To obtain spin temperatures and corrected HI column densities, suitable Off-position spectra were acquired, making use of the three Galactic plane surveys: Canadian Galactic Plane Survey (CGPS, Taylor et al., 2003AJ....125.3145T), Southern Galactic Plane Survey (SGPS, McClure-Griffiths et al., 2005ApJS..158..178M), and VLA Galactic Plane Survey (VGPS, Stil et al., 2006AJ....132.1158S). Furthermore, for some of the sight lines 550-GHz HF spectra are available, observed with the Herschel space telescope. With these, the molecular hydrogen column density can be estimated, and in combination with the HI column densities, the molecular fraction is determined. The calculation of all result spectra was done with Bayesian Markov-Chain Monte Carlo using the Python PyMC3 framework (Patil, Huard, and Fonnesbeck, DOI: 10.18637/jss.v035.i04). In the FITS binary tables, provided here, the results of our Bayes sampling are contained. For each sight line, we provide seven spectra per quantity (i.e, the -3, -2, -1, 0, 1, 2, and 3 confidence levels) plus the full Bayes chains (1000 steps) for the following variables: Tcsou, Tcbg, tau, Tspin, NHI, NH2, and F{H2/H}, because the latter are not Normal distributed. Objects: --------------------------------------------------------------- RA (2000) DE Designation(s) --------------------------------------------------------------- 17 47 20.4 -28 23 07 SGRB2 = SGR B2 18 10 28.6 -19 55 51 G10.62-0.39 = W 31 18 14 39.0 -17 52 03 W33A = W 33A 18 47 34.6 -01 12 43 G31.41+0.31 = GAL 031.41+00.31 18 53 18.5 +01 14 58 G34.26+0.15 = GAL 034.26+00.15 19 10 13.2 +09 06 12 W49N = W 49N 19 23 43.9 +14 30 30 W51E4 = W 51E4 20 39 01.0 +42 22 50 DR21(OH) = DR 21 (OH) --------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file sources.dat 67 8 List of observed sources sightlin.dat 70 31 List of analyzed sight lines fits/* 0 8 Individial fits tables with distributions and Bayes chain
See also: J/A+A/542/A110 : Neutral gas in the Milky Way halo (Ben Bekhti+, 2012) Byte-by-byte Description of file: sources.dat
Bytes Format Units Label Explanations
1- 11 A11 --- Name Source name 13- 14 I2 h RAh Right ascension (J2000.0) of phase center 16- 17 I2 min RAm Right ascension (J2000.0) of phase center 19- 22 F4.1 s RAs Right ascension (J2000.0) of phase center 24 A1 --- DE- Declination sign (J2000.0) of phase center 25- 26 I2 deg DEd Declination (J2000.0) of phase center 28- 29 I2 arcmin DEm Declination (J2000.0) of phase center 31- 32 I2 arcsec DEs Declination (J2000.0) of phase center 34- 40 F7.4 deg GLON Galactic longitude of phase center 42- 48 F7.4 deg GLAT Galactic latitude of phase center 50 I1 --- SLnum Number of extracted sight lines 52- 67 A16 --- FileName Associated FITS file in subdirectory fits
Byte-by-byte Description of file: sightlin.dat
Bytes Format Units Label Explanations
1- 11 A11 --- Name Source name 13- 16 A4 --- ID Sight line ID 18- 19 I2 h RAh Right ascension (J2000.0) of sight line 21- 22 I2 min RAm Right ascension (J2000.0) of sight line 24- 27 F4.1 s RAs Right ascension (J2000.0) of sight line 29 A1 --- DE- Declination sign (J2000.0) of sight line 30- 31 I2 deg DEd Declination (J2000.0) of sight line 33- 34 I2 arcmin DEm Declination (J2000.0) of sight line 36- 37 I2 arcsec DEs Declination (J2000.0) of sight line 39- 45 F7.4 deg GLON Galactic longitude of sight line 47- 53 F7.4 deg GLAT Galactic latitude of sight line 55- 70 A16 --- FileName Associated FITS file in subdirectory fits
Acknowledgements: Benjamin Winkel, bwinkel(at)mpifr.de
(End) Patricia Vannier [CDS] 26-Jan-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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