ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: THE INFRARED EXCESS OF UV-SELECTED z = 2–10 GALAXIES AS A FUNCTION OF UV-CONTINUUM SLOPE AND STELLAR MASS

Abstract

We make use of deep 1.2 mm-continuum observations (12.7µJy/beam RMS) of a 1 arcmin 2 region in the Hubble Ultra Deep Field (HUDF) to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2-10 (to ∼2-3 M ⊙ /yr at 1σ over the entire range). Given the depth and area of ASPECS, we would expect to tentatively detect 35 galaxies extrapolating the Meurer z ∼ 0 IRX-β relation to z ≥ 2 (assuming T d ∼ 35 K). However, only 6 tentative detections are found at z 2 in ASPECS, with just three at >3σ. Subdividing z = 2-10 galaxies according to stellar mass, U V luminosity, and U V -continuum slope and stacking the results, we only find a significant detection in the most massive (>10 9.75 M ⊙ ) subsample, with an infrared excess (IRX=L IR /L UV ) consistent with previous z ∼ 2 results. However, the infrared excess we measure from our large selection of sub-L * (<10 9.75 M ⊙ ) galaxies is 0.11 +0.32 −0.42 ±0.34 (bootstrap and formal uncertainties) and 0.14 +0.15 −0.14 ±0.18 at z = 2-3 and z = 4-10, respectively, lying below even an SMC IRX-β relation (95% confidence). These results demonstrate the relevance of stellar mass for predicting the IR luminosity of z 2 galaxies. We find that the evolution of the IRX-stellar mass relationship depends on the evolution of the dust temperature. If the dust temperature increases monotonically with redshift (∝ (1 + z) 0.32 ) such that T d ∼ 44-50 K at z ≥ 4, current results are suggestive of little evolution in this relationship to z ∼ 6. We use these results to revisit recent estimates of the z ≥ 3 star-formation rate density.

High-redshift Galaxies and Black Holes Detectable with the JWST: A Population Synthesis Model from Infrared to X-Rays

“…The errors are propagated errors and are assumed to be uncorrelated, and no error on the slope of the relation between A UV and β is reported in the literature. This relation produces values similar to the model with no evolution in the relation between infrared excess and stellar mass of Bouwens et al (2016). We do not decrease A UV below 0.5 in order to obtain a reasonable fit of the faint end of the galaxy LF.…”

The dust content of galaxies from z = 0 to z = 9

“…Aravena et al 2016;Bouwens et al 2016;Dunlop et al 2017). The buildup of the dust mass function suggests that (depending on the sensitivity) blind surveys are most likely to pick up galaxies with redshifts lower than three (see for example Figure 8 in Aravena et al (2016) and Figure 5 in Dunlop et al (2017)).…”

The Alma Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular Gas Reservoirs in High-Redshift Galaxies

“…In other papers of this series, we present the data set and the catalog of blindly selected CO emitters (Paper I, Walter et al 2016), we study the properties of 1.2 mm detected sources (Paper II, Aravena et al 2016a), we discuss the inferred constraints on the luminosity functions of CO (Paper III, Decarli et al 2016a), and we search for [C II] emission in z=6-8 galaxies (Paper V, Aravena et al 2016b). Paper VI (Bouwens et al 2016) places our findings in the context of the dust extinction law for > z 2 galaxies, and Paper VII (Carilli et al 2016) uses ASPECS to place first direct constraints on intensity mapping experiments. Here we place the CO detections in the context of the properties of the associated galaxies.…”