Zusammenfassung
We study the sub-mm properties of color-selected galaxies via a stacking
analysis applied for the first time to interferometric data at sub-mm
wavelengths. We base our study on 344 GHz ALMA continuum observations of
~20''-wide fields centered on 86 sub-mm sources detected in the LABOCA Extended
Chandra Deep Field South Sub-mm Survey (LESS). We select various classes of
distant galaxies (K-selected, star-forming sBzK galaxies, extremely red objects
and distant red galaxies) according to their optical and NIR fluxes. We find
clear, >10-sigma detections in the stacked images of all galaxy classes
considered in our study. We include in our stacking analysis Herschel/SPIRE
data to constrain the dust SED of these galaxies. We find that their dust
emission is well described by a modified black body with Tdust~30 K and
beta=1.6 and IR luminosities of (5-11) x 10^11 Lsun, or implied star
formation rates between 75 and 140 Msun/yr. We compare our results with those
of previous studies of these galaxy populations based on single-dish
observations at 870 micron and find that our flux densities are a factor 2-3
higher than previous estimates. The discrepancy is observed also when we remove
sources individually detected in ALESS maps (<35% of the galaxies in all the
samples). We report a similar discrepancy by repeating our analysis on 1.4 GHz
interferometric observations of the whole ECDFS. Hence we find tentative
evidence that galaxies that are associated in projected and redshift space with
sub-mm bright sources are brighter than the average population. Finally, we put
our findings in the context of the cosmic star formation rate density as a
function of z.
Nutzer