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

Bouwens, Rychard J, Aravena, Manuel, Decarli, Roberto, Walter, Fabian E, Da Cunha, Elisabete, 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 and Wilkins, Steve (2016) 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. Astrophysical Journal, 833 (1). ISSN 0004-637X

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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⊙ 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 Td ∼ 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 Me) subsample, with an infrared excess (IRX = LIR/LUV) 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 (µ +1 z 0.32 ( ) ) such that Td ∼ 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.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Depositing User: Stephen Wilkins
Date Deposited: 01 Mar 2017 11:38
Last Modified: 06 Mar 2017 16:01
URI: http://sro.sussex.ac.uk/id/eprint/66951

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