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

Rychard J. Bouwens, Manuel Aravena, Roberto Decarli, Fabian Walter, Elisabete Da Cunha, Ivo Labbé, Franz Bauer, Frank Bertoldi, Chris Carilli, Scott Chapman, Emanuele Daddi, Jacqueline Hodge, Rob J. Ivison, Alex Karim, Olivier Le Fevre, Benjamin Magnelli, Kazuaki Ota, Dominik Riechers, Ian Smail, Paul Van Der WerfAxel Weiss, Pierre Cox, David Elbaz, Jorge Gonzalez-Lopez, Leopoldo Infante, Pascal Oesch, Jeff Wagg, Steve Wilkins

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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 o 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 o) 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 (<109.75Mo) galaxies is ±0.34 (bootstrap and formal uncertainties) and ±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 () 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.

Original languageEnglish
Article number72
JournalAstrophysical Journal
Volume833
Issue number1
DOIs
Publication statusPublished - 10 Dec 2016
Externally publishedYes

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