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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 125 11303 IRDC properties
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See also:
J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/A+A/590/A72 : Herschel counterparts of SDC (Peretto+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Acknowledgements:
Nicolas Peretto, nicolas.peretto(at)manchester.ac.uk
(End) Nicolas Peretto [JBCfA, University of Manchester, UK] 13-Jul-2009