A deep ALMA image of the Hubble Ultra Deep Field

J. S. Dunlop, R. J. McLure, A. D. Biggs, J. E. Geach, M. J. Michałowski, R. J. Ivison, W. Rujopakarn, E. van Kampen, A. Kirkpatrick, A. Pope, D. Scott, A. M. Swinbank, T. A. Targett, I. Aretxaga, J. E. Austermann, P. N. Best, V. A. Bruce, E. L. Chapin, S. Charlot, M. CirasuoloK. Coppin, R. S. Ellis, S. L. Finkelstein, C. C. Hayward, D. H. Hughes, E. Ibar, P. Jagannathan, S. Khochfar, M. P. Koprowski, D. Narayanan, K. Nyland, C. Papovich, J. A. Peacock, G. H. Rieke, B. Robertson, T. Vernstrom, P. P. van der Werf, G. W. Wilson, M. Yun

Research output: Contribution to journalArticlepeer-review

Abstract

We present the results of the first, deep Atacama Large Millimeter Array(ALMA) imaging covering the full ≃4.5 arcmin2 of theHubble Ultra Deep Field (HUDF) imaged with Wide Field Camera 3/IR onHST. Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mmimage reaching σ1.3 ≃ 35 μJy, at a resolutionof ≃0.7 arcsec. From an initial list of ≃50 > 3.5σpeaks, a rigorous analysis confirms 16 sources with S1.3 >120 μJy. All of these have secure galaxy counterparts with robustredshifts ( = 2.15). Due to the unparalleled supporting data,the physical properties of the ALMA sources are well constrained,including their stellar masses (M*) and UV+FIR star formationrates (SFR). Our results show that stellar mass is the best predictor ofSFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA samplecontains seven of the nine galaxies in the HUDF with M* ≥2 × 1010 M⊙, and we detect only onegalaxy at z > 3.5, reflecting the rapid drop-off of high-massgalaxies with increasing redshift. The detections, coupled withstacking, allow us to probe the redshift/mass distribution of the 1.3-mmbackground down to S1.3 ≃ 10 μJy. We find strongevidence for a steep star-forming `main sequence' at z ≃ 2, withSFR ∝M* and a mean specific SFR ≃ 2.2Gyr-1. Moreover, we find that ≃85 per cent of total starformation at z ≃ 2 is enshrouded in dust, with ≃65 per cent ofall star formation at this epoch occurring in high-mass galaxies(M* > 2 × 1010 M⊙), forwhich the average obscured:unobscured SF ratio is ≃200. Finally, werevisit the cosmic evolution of SFR density; we find this peaks at z≃ 2.5, and that the star-forming Universe transits from primarilyunobscured to primarily obscured at z ≃ 4.
Original languageEnglish
Pages (from-to)861-883
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Volume466
Issue number1
Early online date30 Nov 2016
DOIs
Publication statusPublished - 1 Apr 2017

Keywords

  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: starburst
  • cosmology: observations
  • submillimetre: galaxies

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