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J/A+A/505/405     A catalogue of Spitzer dark clouds            (Peretto+, 2009)

The initial conditions of stellar protocluster formation. I. A catalogue of Spitzer dark clouds. Peretto N., Fuller G.A. <Astron. Astrophys. 505, 405 (2009)> =2009A&A...505..405P
ADC_Keywords: Infrared sources ; Molecular clouds ; Morphology Keywords: catalogs - stars: formation - ISM: clouds Abstract: The majority of stars form in clusters. Therefore a comprehensive view of star formation requires understanding the initial conditions for cluster formation. The goal of our study is to shed light on the physical properties of infrared dark clouds (IRDCs) and the role they play in the formation of stellar clusters. This article, the first of a series dedicated to the study of IRDCs, describes techniques developed to establish a complete catalogue of Spitzer IRDCs in the Galaxy. We have analysed Spitzer GLIMPSE and MIPSGAL data to identify a complete sample of IRDCs in the region of Galactic longitude and latitude 10°<|l|<65° and |b|<1°. From the 8um observations we have constructed opacity maps and used a newly developed extraction algorithm to identify structures above a column density of NH2=1x1022cm-2. The 24um data are then used to characterize the star formation activity of each extracted cloud. A total of 11303 clouds have been extracted. A comparison with the existing MSX based catalogue of IRDCs shows that 80% of these Spitzer dark clouds were previously unknown. The algorithm also extracts ∼20000 to 50000 fragments within these clouds, depending on detection threshold used.A first look at the MIPSGAL data indicates that between 20% and 68% of these IRDCs show 24um point-like association. This new database provides an important resource for future studies aiming to understand the initial conditions of star formation in the Galaxy. Description: Properties of the 11303 IRDCs identified in the galactic plane using GLIMPSE 8um data. For each IRDC we give a running number, the name of the IRDC, the J2000 coordinates, the minimum 8um intensity within the cloud, the mid-infrared radiation field intensity, the normalized mid-infrared radiation field variation, the major and minor axes of the IRDC, the position angle, the equivalent radius, the 8um peak opacity, the 8um opacity averaged over the IRDC, the 8um saturation opacity, the number of fragments within the clouds (calculated), a letter indicating if any 24um stars have been identified within the IRDC boundaries and within a larger area around the IRDC, the 24um star surface density around the IRDC (a short version of this table is available in the paper). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 125 11303 IRDC properties
See also: J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006) J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Seq Running number 7- 9 A3 --- --- [SDC] 10- 22 A13 --- Name IRDC (Infra-Red Dark Cloud) name, based on Galactic position (LLL.ll+B.bbb) 24- 25 I2 h RAh Right Ascension J2000 (hours) 27- 28 I2 min RAm Right Ascension J2000 (minutes) 30- 34 F5.2 s RAs [0/60] Right Ascension J2000 (seconds) 36 A1 --- DE- Sign declination J2000 38- 39 I2 deg DEd Declination J2000 (degrees) 41- 42 I2 arcmin DEm Declination J2000 (arcminutes) 44- 47 F4.1 arcsec DEs [0/60] Declination J2000 (arcseconds) 49- 54 F6.1 MJy/sr Imin Minimum intensity within the IRDC 56- 61 F6.1 MJy/sr IMIR Mid-IR radiation field intensity 63- 67 F5.2 --- dIMIR Normalized variation of IMIR 69- 74 F6.1 arcsec maj Major axis size of IRDC 76- 81 F6.1 arcsec min Minor axis size of IRDC 83- 86 I4 deg PA [-90,90] Position angle of IRDC 88- 93 F6.1 arcsec Req Equivalent radius of IRDC 95- 99 F5.2 --- tau.p 8micron peak opacity of IRDC 101-105 F5.2 --- tau.av 8micron averaged opacity of IRDC 107-111 F5.2 --- tau.sat 8micron saturation opacity 113-115 I3 --- Nfr Number of fragments (with tau_step=0.35: cf paper) 117 A1 --- Field [y/n] 24micron star in the field: y for yes, n for no 119 A1 --- IRDC [y/n] 24micron star in the IRDC: y for yes, n for no 121-125 F5.2 arcmin-2 Sigma 24micron star surface density around the IRDC
Acknowledgements: Nicolas Peretto, nicolas.peretto(at)manchester.ac.uk
(End) Nicolas Peretto [JBCfA, University of Manchester, UK] 13-Jul-2009
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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