Faint Submillimeter Counts from Deep 850 Micron Observations of the Lensing Clusters A370, A851, and A2390

Abstract

We present deep 850 lm maps of three massive lensing clusters, A370, A851, and A2390, with wellconstrained mass models. Our cluster exposure times are more than 2-5 times longer than any other published cluster field observations. We catalog the sources and determine the submillimeter number counts. The counts are best determined in the 0.3-2 mJy range, where the areas are large enough to provide a significant sample. At 0.3 mJy the cumulative counts are 3:3 þ6:3 À1:3 Â 10 4 deg À2 , where the upper and lower bounds are the 90% confidence range. The surface density at these faint count limits enters the realm of significant overlap with other galaxy populations. The corresponding percentage of the extragalactic background light (EBL) residing in this flux range is about 45%-65%, depending on the EBL measurement used. Given that 20%-30% of the EBL is resolved at flux densities between 2 and 10 mJy, most of the submillimeter EBL is arising in sources above 0.3 mJy. We also performed a noise analysis to obtain an independent estimate of the counts. The upper bounds on the counts determined from the noise analysis closely match the upper limits obtained from the direct counts. The differential counts from this and other surveys can reasonably be described by the parameterization nðSÞ ¼ 3 Â 10 4 deg À2 mJy À1 =ð0:7 þ S 3:0 Þ with S in mJy, which also integrates to match the EBL.

Dusty star-forming galaxies at high redshift

“…The Cowie et al (2002) results do not quote uncertainties and the Barnard et al (2004) results represent upper limits on number counts at very high flux densities, covering larger areas than the nominal Scuba survey. The work of Blain et al (1999), Smail et al (2002), Cowie et al (2002), Knudsen et al (2008) and Chen et al (2013a) used gravitational lensing in cluster fields to survey flux densities <1 mJy. Oliver et al, 2010;Clements et al, 2010;Béthermin et al, 2010bBéthermin et al, , 2012b, and 1.1 mm Austermann et al, 2010;Scott et al, 2010;Hatsukade et al, 2011;Aretxaga et al, 2011;Scott et al, 2012).…”

“…This technique was first outlined by Eales et al (2000), Scott et al (2002) and Cowie et al (2002) and used in Borys et al (2003) for the Scuba HDF survey and in Coppin et al (2006) for the Scuba SHADES survey. It has since been updated for point source identification in Herschel extragalactic surveys such as HerMES , but probably the most elegant updates to the technique have come out of work done by the AzTEC team (see Perera et al, 2008;Scott et al, 2008;Austermann et al, 2010;Scott et al, 2012).…”

“…Figure 12 illustrates both 850-870µm number counts (from Scuba, Laboca, Scuba-2, and ALMA Blain et al, 1999;Scott et al, 2002;Chapman et al, 2002;Cowie et al, 2002;Borys et al, 2003;Webb et al, 2003;Barnard et al, 2004;Coppin et al, 2006;Scott et al, 2006;Knudsen et al, 2008;Beelen et al, 2008;Weiß et al, 2009a;Karim et al, 2013;Casey et al, 2013;Chen et al, 2013a) and 450-500µm (from Scuba, Herschel and Scuba-2 Smail et al, 2002;Oliver et al, 2010;Clements et al, 2010;Béthermin et al, 2012b;Geach et al, 2013;Casey et al, 2013;Chen et al, 2013a). Figure 13 illustrates other infrared and submillimeter number counts in the literature in direct units, from 70µm Béthermin et al, 2010a;Berta et al, 2011), 100µm (Héraudeau et al, 2004;Rodighiero & Franceschini, 2004;Kawara et al, 2004;Berta et al, 2011;Magnelli et al, 2013b), 160µm Kawara et al, 2004;Béthermin et al, 2010a;Berta et al, 2011;Magnelli et al, 2013b), 250µm and 350µm Chen+13 (850) Casey+13 (850 Figure 12: Differential submillimeter number counts at 850µm/870µm (left) and 450-500 µm (right).…”

“…Figure 13 illustrates other infrared and submillimeter number counts in the literature in direct units, from 70µm Béthermin et al, 2010a;Berta et al, 2011), 100µm (Héraudeau et al, 2004;Rodighiero & Franceschini, 2004;Kawara et al, 2004;Berta et al, 2011;Magnelli et al, 2013b), 160µm Kawara et al, 2004;Béthermin et al, 2010a;Berta et al, 2011;Magnelli et al, 2013b), 250µm and 350µm Chen+13 (850) Casey+13 (850 Figure 12: Differential submillimeter number counts at 850µm/870µm (left) and 450-500 µm (right). The 850µm and 870µm number counts come the initial Scuba surveys Scott et al, 2002;Chapman et al, 2002;Cowie et al, 2002;Borys et al, 2003;Webb et al, 2003;Barnard et al, 2004;Coppin et al, 2006;Scott et al, 2006;Knudsen et al, 2008, , shown in brown, dark red, red, dark orange, orange, dark gold yellow, light green, green, dark teal, and teal respectively). Data from Beelen et al (2008), Weiß et al (2009a), and Karim et al (2013) are taken at 870µm rather than 850µm, the two former from Laboca and the latter from interferometric ALMA data.…”

“…Scuba-2 850µm data from Casey et al (2013) and Chen et al (2013b) are also plotted, the latter including the lens field work of Chen et al (2013a). The Cowie et al (2002) results do not quote uncertainties and the Barnard et al (2004) results represent upper limits on number counts at very high flux densities, covering larger areas than the nominal Scuba survey. The work of Blain et al (1999), Smail et al (2002), Cowie et al (2002), Knudsen et al (2008) and Chen et al (2013a) used gravitational lensing in cluster fields to survey flux densities <1 mJy.…”