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Galaxy counts at 24 mu m in the SWIRE fields

journal contribution
posted on 2023-06-08, 09:28 authored by David L Shupe, Michael Rowan-Robinson, Carol J Lonsdale, Frank Masci, Tracey Evans, Fan Fang, Seb OliverSeb Oliver, Mattia Vaccari, Giulia Rodighiero, Deborah Padgett, Jason A Surace, C Kevin Xu, Stefano Berta, Francesca Pozzi, Alberto Franceschini, Thomas Babbedge, Eduardo Gonzales-Solares, Brian D Siana, Duncan Farrah, David T Frayer, H E Smith, Maria Polletta, Frazer Owen, Ismael Pérez-Fournon
This paper presents galaxy source counts at 24 mu m 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 mu m 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 mu Jy, about 25% are between z similar to 0.3 and 0.8, and a significant fraction are at z similar to 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.


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Astronomical Journal




American Astronomical Society





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  • Physics and Astronomy Publications


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