Properties of submillimetre galaxies in a semi-analytic model using the ‘Count Matching’ approach: application to the ECDF-S

Abstract

We present a new technique for modelling submillimetre galaxies (SMGs): the 'Count Matching' approach. Using light cones drawn from a semi-analytic model of galaxy formation, we choose physical galaxy properties given by the model as proxies for their submillimetre luminosities, assuming a monotonic relationship. As recent interferometric observations of the Extended Chandra Deep Field-South show that the brightest sources detected by single-dish telescopes are comprised by emission from multiple fainter sources, we assign the submillimetre fluxes so that the combined Large APEX BOlometer CAmera (LABOCA) plus bright-end Atacama Large Millimeter/submillimeter Array observed number counts for this field are reproduced. After turning the model catalogues given by the proxies into submillimetre maps, we perform a source extraction to include the effects of the observational process on the recovered counts and galaxy properties. We find that for all proxies, there are lines of sight giving counts consistent with those derived from LABOCA observations, even for input sources with randomized positions in the simulated map. Comparing the recovered redshift, stellar mass and host halo mass distributions for model SMGs with observational data, we find that the best among the proposed proxies is that in which the submillimetre luminosity increases monotonically with the product between dust mass and star formation rate (SFR). This proxy naturally reproduces a positive trend between SFR and bolometric IR luminosity. The majority of components of blended sources are spatially unassociated.

The clustering evolution of dusty star-forming galaxies

“…Our results for stellar and halo masses of bright SMGs and their descendants are a factor of ∼5 lower than those found by Muñoz Arancibia et al (2015). However, their simulations do not selfconsistently predict the sub-mm flux of galaxies as is done in this work, but instead rely on a 'count-matching' approach to link a galaxy's physical properties to its sub-mm flux.…”

“…Although not shown 8 In Cowley et al (2015), we showed that this confusion effect boosts the cumulative 850 μm number counts by a factor of ∼2 at S 850 μm = 4 mJy for a 15 arcsec FWHM beam. See also Hayward et al (2013) and Muñoz Arancibia et al (2015), who investigate the effect of coarse angular resolution on the observed sub-mm number counts. Fig.…”

MultiDark-Galaxies: data release and first results

“…SAG model originates from a version of the Munich code (Springel et al 2001) and has been further developed and improved as described in Cora (2006), Lagos et al (2008), Tecce et al (2010a), Orsi et al (2014), Muñoz Arancibia et al (2015) and Gargiulo et al (2015). The latest version of the model is presented by Cora et al (in prep.).…”

HerMES: ALMA IMAGING OFHERSCHEL-SELECTED DUSTY STAR-FORMING GALAXIES

“…However, it is also possible that the sources are merely unrelated galaxies that appear blended due to projection effects (Hayward et al 2013a;Cowley et al 2015;Muñoz Arancibia et al 2015). Spatially resolved spectroscopy is necessary to answer this question definitively, but is not currently available.…”