Dust attenuation in 2 < z < 3 star-forming galaxies from deep ALMA observations of the Hubble Ultra Deep Field

R. J. McLure, J. S. Dunlop, F. Cullen, N. Bourne, P. N. Best, S. Khochfar, R. A. A. Bowler, A. D. Biggs, J. E. Geach, D. Scott, M. J. Michałowski, W. Rujopakarn, E. van Kampen, A. Kirkpatrick, A. Pope

Research output: Contribution to journalArticlepeer-review

Abstract

We present the results of a new study of the relationship betweeninfrared excess (IRX≡ LIR/LUV), UV spectralslope (β) and stellar mass at redshifts 2 <z <3, based on adeep Atacama Large Millimeter Array (ALMA) 1.3-mm continuum mosaic ofthe Hubble Ultra Deep Field (HUDF). Excluding the most heavily-obscuredsources, we use a stacking analysis to show that z ≃ 2.5star-forming galaxies in the mass range 9.25≤ log (M_{\ast}/M_{⊙}) ≤ 10.75 are fully consistent with the IRX-βrelation expected for a relatively grey attenuation curve, similar tothe commonly adopted Calzetti law. Based on a large, mass complete,sample of 2 ≤ z ≤ 3 star-forming galaxies drawn from multiplesurveys, we proceed to derive a new empirical relationship betweenβ and stellar mass, making it possible to predict UV attenuation(A1600) and IRX as a function of stellar mass, for anyassumed attenuation law. Once again, we find that z ≃ 2.5star-forming galaxies follow A1600-M* andIRX-M* relations consistent with a relatively greyattenuation law, and find no compelling evidence that star-forminggalaxies at this epoch follow a reddening law as steep as the SmallMagellanic Cloud (SMC) extinction curve. In fact, we use a simplesimulation to demonstrate that previous determinations of the IRX-βrelation may have been biased toward low values of IRX at red values ofβ, mimicking the signature expected for an SMC-like dust law. Weshow that this provides a plausible mechanism for reconciling apparentlycontradictory results in the literature and that, based on typicalmeasurement uncertainties, stellar mass provides a cleaner prediction ofUV attenuation than β. Although the situation at lower stellarmasses remains uncertain, we conclude that for 2 <z <3star-forming galaxies with log (M_{\ast }/M_{⊙}) ≥ 9.75, both theIRX-β and IRX-M* relations are well described by aCalzetti-like attenuation law.
Original languageEnglish
Pages (from-to)3991–4006
JournalMonthly Notices of the Royal Astronomical Society
Volume476
Issue number3
DOIs
Publication statusPublished - 6 Mar 2018

Keywords

  • galaxies: high-redshift
  • galaxies: evolution
  • galaxies: starburst
  • galaxies: star formation
  • submillimetre: galaxies

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