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, R.J.; Aravena, M.; Decarli, R.; Walter, F.; da Cunha, E.; Labbé, I.; Bauer, F.E.; Bertoldi, F.; Carilli, C.; Chapman, S.; Daddi, E.; Hodge, J.; Ivison, R.J.; Karim, A.; Le Fevre, O.; Magnelli, B.; Ota, K.; Riechers, D.; Smail, I.R.; van der Werf, P.; Weiss, A.; Cox, P.; Elbaz, D.; Gonzalez-Lopez, J.; Infante, L.; Oesch, P.; Wagg, J.; Wilkins, S.

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.

Citation

Bouwens, R., Aravena, M., Decarli, R., Walter, F., da Cunha, E., Labbé, I., …Wilkins, S. (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), Article 72. https://doi.org/10.3847/1538-4357/833/1/72

• Journal Article Type: Article
• Acceptance Date: Aug 3, 2016
• Online Publication Date: Dec 8, 2016
• Publication Date: Dec 8, 2016
• Deposit Date: Feb 22, 2017
• Publicly Available Date: Mar 9, 2017
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 833
• Issue: 1
• Article Number: 72
• DOI: https://doi.org/10.3847/1538-4357/833/1/72
• Public URL: https://durham-repository.worktribe.com/output/1385120
• Related Public URLs: http://sro.sussex.ac.uk/id/eprint/66951/