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

Journal
Date Issued
2016
Author(s)
Bouwens, Rychard J.
•
Aravena, Manuel
•
•
Walter, Fabian
•
Labbé, Ivo
•
Bauer, Franz E.
•
Bertoldi, Frank
•
Carilli, Chris
•
Chapman, Scott
•
Daddi, Emanuele
•
Hodge, Jacqueline
•
Ivison, Rob J.
•
Karim, Alex
•
Le Fevre, Olivier
•
Magnelli, Benjamin
•
Ota, Kazuaki
•
Riechers, Dominik
•
Smail, Ian R.
•
van der Werf, Paul
•
Weiss, Axel
•
Cox, Pierre
•
Elbaz, David
•
Gonzalez-Lopez, Jorge
•
Infante, Leopoldo
•
Oesch, Pascal
•
Wagg, Jeff
•
Wilkins, Steve
DOI
Abstract
We make use of deep 1.2 mm continuum observations (12.7 μJy beam-1 rms) of a 1 arcmin2 region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2-10 (to ∼2-3 M ☉ yr-1 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 dust temperature T d ∼ 35 K). However, only six tentative detections are found at z ≳ 2 in ASPECS, with just three at >3σ. Subdividing our z = 2-10 galaxy samples according to stellar mass, UV luminosity, and UV-continuum slope and stacking the results, we find a significant detection only in the most massive (>109.75 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 ∗ (<109.75 M ☉) galaxies is {0.11}-0.42+0.32 ± 0.34 (bootstrap and formal uncertainties) and {0.14}-0.14+0.15 ± 0.18 at z = 2-3 and z = 4-10, respectively, lying below even an IRX-β relation for the Small Magellanic Cloud (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 (\propto {(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.
Volume
833
Issue
1
Start page
72
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...833...72B
Rights
open.access
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