Shupe, David L. and Rowan-Robinson, Michael and Lonsdale, Carol J. and Masci, Frank and Evans, Tracey and Fang, Fan and Oliver, Sebastian and Vaccari, Mattia and Rodighiero, Giulia and Padgett, Deborah and Surace, Jason A. and Xu, C. Kevin and Berta, Stefano and Pozzi, Francesca and Franceschini, Alberto and Babbedge, Thomas and Gonzales-Solares, Eduardo and Siana, Brian D. and Farrah, Duncan and Frayer, David T. and Smith, H. E. and Polletta, Maria and Owen, Frazer and Pérez-Fournon, Ismael (2008) Galaxy counts at 24 μm in the SWIRE fields. Astronomical Journal, 135 (3). pp. 1050-1056. ISSN 0004-6256 http://resolver.caltech.edu/CaltechAUTHORS:20090428-130122358
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This paper presents galaxy source counts at 24 μm in the six Spitzer Wide-field InfraRed Extragalactic (SWIRE) fields. The source counts are compared to counts in other fields, and to model predictions that have been updated since the launch of Spitzer. This analysis confirms a very steep rise in the Euclidean-normalized differential number counts between 2 mJy and 0.3 mJy. Variations in the counts between fields show the effects of sample variance in the flux range of 0.5-10 mJy, up to 100% larger than Poisson errors. Nonetheless, a "shoulder" in the normalized counts persists at around 3 mJy. The peak of the normalized counts at 0.3 mJy is higher and narrower than most models predict. In the ELAIS N1 field, the 24 μm data are combined with Spitzer-IRAC data and five-band optical imaging, and these band-merged data are fit with photometric redshift templates. Above 1 mJy the counts are dominated by galaxies at z < 0.3. By 300 μJy, about 25% are between z ~ 0.3 and 0.8, and a significant fraction are at z ~ 1.3-2. At low redshifts the counts are dominated by spirals, and starbursts rise in number density to outnumber the spirals' contribution to the counts below 1 mJy.
|Additional Information:||© 2008 The American Astronomical Society. Received 2006 June 27; accepted 2007 November 3; published 2008 February 14. We are grateful to the referees for their comments, which have led to substantial improvement of this paper. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. SB was supported by a Fondazione Ing. Aldo Gini 2006 grant.|
|Subject Keywords:||cosmology: observations; galaxies: evolution; galaxies: starburst; infrared: galaxies; stars: formation|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||09 Jul 2009 23:42|
|Last Modified:||26 Dec 2012 10:58|
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