An Alma Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: The Redshift Distribution and Evolution of Submillimeter Galaxies

Abstract

We present the first photometric redshift distribution for a large sample of 870 µm SMGs with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the ECDFS, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of z phot = 2.3 ± 0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z ∼ 1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to z phot = 2.5 ± 0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z ≥ 3 is at most 35 ± 5 per cent of the total population. We derive a median stellar mass of M ⋆ = (8 ± 1) × 10 10 M ⊙ , although there are systematic uncertainties of up to 5 × for individual sources. Assuming that the star formation activity in SMGs has a timescale of ∼ 100 Myr we show that their descendants at z ∼ 0 would have a space density and M H distribution which are in good agreement with those of local ellipticals. In addition the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events which form most of the stars seen in the majority of luminous elliptical galaxies at the present day.

Estimating sizes of faint, distant galaxies in the submillimetre regime

“…We also fit the position using the disc and Gaussian models, finding a variation of ∼0.02 arcsec between the different models. This is consistent with the offset found by Simpson et al (2014) for the bright galaxies in the same data. Based on this, all stacked data sets were phase rotated with 0.3 arcsec in declination.…”

“…The selection is based on the photometric catalogue of the ECDFS assembled using the same procedure as Simpson et al (2014), using primarily data from the Wide MUltiwavelength Survey by Yale-Chile (MUSYC; Taylor et al 2009). The MUSYC catalogue is a K-band flux limited sample, covering a 30 arcmin × 30 arcmin area of the ECDFS, with photometry for the sources in the bands UBVRIzJHK.…”

“…At K AB = 22 mag, the sample is 100 per cent complete for point sources, and 96 per cent complete for extended sources with a scale radius of 0.5 arcsec. Simpson et al (2014) extend the catalogue by including a deep J and K band catalogue Zibetti et. al (in preparation), the Taiwan ECDFS NIR survey (Hsieh et al 2012), and Spitzer/IRAC 3.6, 4.5, 5.8, and 8.0 µm images from the Spitzer IRAC/MUSYC Public Legacy Survey (Damen et al 2011).…”

Dusty star-forming galaxies at high redshift

“…Also over-plotted is the Lewis et al (2005) and Chapman et al (2003b) phenomenological model 850µm SMG redshift distribution without radio flux selection (dark green dot dashed line). We also over-plot the Wardlow et al (2011) redshift distribution for the LESS 870µm sample in CDFS (red line filled histogram) and the update to that sample−courtesy of ALMA follow-up establishing unambiguous counterparts− from Simpson et al (2013) in orange. The latter is plotted in equal-time redshift bins to account for duty cycle correction.…”

The clustering evolution of dusty star-forming galaxies

“…Sanders & Mirabel 1996), but whether this is the dominant triggering mechanism at the peak of the SMG redshift distribution (z ∼ 2.5; e.g. Chapman et al 2005;Simpson et al 2014) is unclear. Some dynamical studies using emission lines from the 12 CO molecule (e.g.…”