Cores in infrared dark clouds (IRDCs) seen in the Hi-GAL survey between l= 300° and 330°

Wilcock, Lucy Ann, Ward-Thompson, Derek, Kirk, Jason M., Stamatellos, Dimitrios, Whitworth, Anthony Peter, Elia, D., Fuller, G. A., DiGiorgio, A., Griffin, Matthew Joseph, Molinari, S., Martin, P., Mottram, J. C., Peretto, Nicolas, Pestalozzi, M., Schisano, E., Plume, R., Smith, H. A. and Thompson, M. A. 2012. Cores in infrared dark clouds (IRDCs) seen in the Hi-GAL survey between l= 300° and 330°. Monthly Notices of the Royal Astronomical Society 422 (2) , pp. 1071-1082. 10.1111/j.1365-2966.2012.20680.x

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Abstract

We have used data taken as part of the Herschel infrared Galactic Plane survey (Hi-GAL) to study 3171 infrared dark cloud (IRDC) candidates that were identified in the mid-IR (8 μm) by Spitzer (we refer to these as ‘Spitzer-dark’ regions). They all lie in the range l= 300–330° and |b|≤ 1°. Of these, only 1205 were seen in emission in the far-IR (250–500 μm) by Herschel (we call these ‘Herschel-bright’ clouds). It is predicted that a dense cloud will not only be seen in absorption in the mid-IR, but will also be seen in emission in the far-IR at the longest Herschel wavebands (250–500 μm). If a region is dark at all wavelengths throughout the mid-IR and far-IR, then it is most likely to be simply a region of lower background IR emission (a ‘hole in the sky’). Hence, it appears that previous surveys, based on Spitzer and other mid-IR data alone, may have overestimated the total IRDC population by a factor of ∼2. This has implications for estimates of the star formation rate in IRDCs in the Galaxy. We studied the 1205 Herschel-bright IRDCs at 250 μm and found that 972 of them had at least one clearly defined 250-μm peak, indicating that they contained one or more dense cores. Of these, 653 (67 per cent) contained an 8-μm point source somewhere within the cloud, 149 (15 per cent) contained a 24-μm point source but no 8-μm source and 170 (18 per cent) contained no 24- or 8-μm point sources. We use these statistics to make inferences about the lifetimes of the various evolutionary stages of IRDCs.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Advanced Research Computing @ Cardiff (ARCCA) Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Uncontrolled Keywords:	stars: formation
Publisher:	Wiley
ISSN:	0035-8711
Last Modified:	06 Jan 2020 03:40
URI:	http://orca.cf.ac.uk/id/eprint/24181

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