The UV spectral slope β and stellar population of most active star-forming galaxies at z ~ 4

Satoshi Yamanaka*, Toru Yamada

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


We investigate a stellar population of star-forming galaxies at z ~ 4 by focusing on the slope of their rest-frame ultraviolet (UV) continuum, β, where fλ α λβ. We investigate a sample of bright Lyman break galaxies (LBGs) with i′ ≤ 26.0 in the Subaru/XMM-Newton Deep Survey field by using a spectral energy distribution fitting analysis. We find that the apparently redder (βobs > −1.73) LBGs tend to be dusty (AV > 1.0), and have young stellar populations (βint < −2.42) and intrinsically active star-forming galaxies (SFR ≳ a few × 102 M yr−1). This means that a significant fraction of the UV-selected LBGs at z ~ 4 contains on-going, active, and dust-obscured star-forming galaxies. We compare the infrared to UV luminosity ratio, which is estimated from our optical/near-infrared data assuming dust attenuation laws, with sub-millimeter observations from previous works. The result suggests that the Calzetti-like dust attenuation law is preferable for active and dusty star-forming LBGs at z = 4. We also find that an extrapolation of the βint–MUV, int relation toward the fainter magnitude range below our sample magnitude limit intersects the βobs–MUV, obs relation previously obtained in deeper narrow-area observations at MUV = −18.9 and β = −1.94, which coincides with the break point of the βobs–MUV, obs relation observed so far. This coincidence suggests that we see an almost dust-free population at MUV, obs ≳ −18.9.

Original languageEnglish
Article number51
JournalPublications of the Astronomical Society of Japan
Issue number3
Publication statusPublished - 2019 Jun 1


  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: starburst

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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