The MOSDEF survey: The dependence of H α-to-UV SFR ratios on SFR and size at z ∼2

Tara Fetherolf, Naveen A. Reddy, Alice E. Shapley, Mariska Kriek, Brian Siana, Alison L. Coil, Bahram Mobasher, William R. Freeman, Ryan L. Sanders, Sedona H. Price, Irene Shivaei, Mojegan Azadi, Laura de Groot, Gene C.K. Leung, Tom O. Zick

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We perform an aperture-matched analysis of dust-corrected H α and UV star formation rates (SFRs) using 303 star-forming galaxies with spectroscopic redshifts 1.36 < zspec < 2.66 from the MOSFIRE Deep Evolution Field survey. By combining H α and H β emission line measurements with multiwaveband resolved Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/3D-HST imaging, we directly compare dust-corrected H α and UV SFRs, inferred assuming a fixed attenuation curve shape and constant SFHs, within the spectroscopic aperture. Previous studies have found that H α and UV SFRs inferred with these assumptions generally agree for typical star-forming galaxies, but become increasingly discrepant for galaxies with higher SFRs (Z100 M⊙ yr-1), with H α-to-UV SFR ratios being larger for these galaxies. Our analysis shows that this trend persists even after carefully accounting for the apertures over which H α and UV-based SFRs (and the nebular and stellar continuum reddening) are derived. Furthermore, our results imply that H α SFRs may be higher in the centres of large galaxies (i.e. where there is coverage by the spectroscopic aperture) compared to their outskirts, which could be indicative of inside-out galaxy growth. Overall, we suggest that the persistent difference between nebular and stellar continuum reddening and high H α-to-UV SFR ratios at the centres of large galaxies may be indicative of a patchier distribution of dust in galaxies with high SFRs.

Original languageEnglish
Pages (from-to)1431-1445
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Nov 1 2021

Bibliographical note

Publisher Copyright:
© 2021 The Author(s).


  • Galaxies: Evolution
  • Galaxies: Fundamental parameters
  • Galaxies: High-redshift
  • Galaxies: Star formation
  • Methods: Data analysis

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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