HERSCHEL-ATLAS GALAXY COUNTS AND HIGH-REDSHIFT LUMINOSITY FUNCTIONS: THE FORMATION OF MASSIVE EARLY-TYPE GALAXIES

Abstract

Exploiting the H-ATLAS Science Demonstration Phase (SDP) survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 µm and at several redshifts z 1, for bright sub-mm galaxies with star formation rates (SFR) 100 M ⊙ yr −1 . We find that the evolution of the comoving LF is strong up to z ≈ 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H 3 × 10 12 M ⊙ ) amounts to ∼ 7 × 10 8 yr. Given the SFRs, which are in the range 10 2 − 10 3 M ⊙ yr −1 , this timescale implies final stellar masses of order of 10 11 − 10 12 M ⊙ . The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z 1. The comparison of the statistics for sub-mm and UV selected galaxies suggests that the dust-free, UV bright phase, is 10 2 times shorter than the sub-mm bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference Spectral Energy Distribution (SED; the one of the z ≈ 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts > 1 but also the counts at wavelengths ranging from 250 µm to ≈ 1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of sub-mm SEDs of z > 1 galaxies around the reference one is rather small.

Dusty star-forming galaxies at high redshift

“…With a surface density for S 500 > 100 mJy lensed DSFGs at the level of 0.2 deg −2 Wardlow et al, 2013;Bussmann et al, 2013), and with close to 1200 deg 2 of Spire imaging data in the Herschel Science Wardlow et al (2013) and 'L13' from Lapi et al (2011). The plot also shows magnification factors of two SPT-selected lensed DSFGs from Hezaveh et al (2013).…”

Herschel-ATLAS:Plancksources in the phase 1 fields

“…Several of these sources have red Herschel colours. We have determined photometric redshifts for these objects using the SMM J2135-0102 SED, that was shown to work quite well for z ≥ 1 Lapi et al 2011). We find that four out of the six H-ATLAS sources that are located inside a circle of radius σ 857 = 4.23/2 2 log 2 arcmin (Planck Collaboration 2011b) centred on G12H29 have 0.75 < z phot < 1.25.…”

“…For the comparison with Planck we scaled down the H-ATLAS flux densities by this factor, except for the rich clump of low-flux galaxies, for which we adopted a correction factor of 1.1 for the strongly lensed galaxy at z = 3.259 and of 1.3 for the surrounding H-ATLAS sources, assumed to be at z ≤ 1. These factors were calculated using the SED of H-ATLAS J142413.9+022304, a strongly lensed sub-mm galaxy at z ≈ 4.24 (Cox et al 2011), for the strongly lensed galaxy and the SED of SMM J2135-0102 ("The Cosmic Eyelash"; Ivison et al 2010;Swinbank et al 2010), that Lapi et al (2011) found to work well for many high-z H-ATLAS galaxies. We denote the colour-corrected flux by the symbol S * .…”

Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

“…In some cases, star formation is thought to proceed in a sporadic manner, particularly at high redshifts, with undisturbed, low-level, continuous star formation being the exception in galaxies rather than the primary mechanism of building stellar Article published by EDP Sciences A90, page 1 of 39 mass (e.g., Kolatt et al 1999;Bell et al 2005;Papovich et al 2005Papovich et al , 2006Nichols et al 2012;Pacifici et al 2013). Violent episodes of star formation, known as starbursts, can dramatically alter the stellar mass of galaxies with sufficient gas reservoirs during the relatively short period that constitutes the lifetime of a starburst (typically ∼100-500 Myr; Swinbank et al 2006;Hopkins et al 2008;McQuinn et al 2009McQuinn et al , 2010bWild et al 2010; though perhaps up to ∼700 Myr for particular populations, e.g., Lapi et al 2011;Gruppioni et al 2013). Such events contribute significantly to the global star formation rate (SFR) of galaxies both in the high-redshift universe (e.g., Somerville et al 2001;Chapman et al 2005;Erb et al 2006;Magnelli et al 2009) and locally (e.g., Brinchmann et al 2004;Kauffmann et al 2004; Lee et al 2006Lee et al , 2009 and are furthermore thought to be a typical phase of evolution undergone by massive quiescent galaxies observed at low redshifts early in their formation history (e.g., Juneau et al 2005;Hickox et al 2012).…”