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

Satoshi Yamanaka; Toru Yamada

doi:10.1093/pasj/psz024

paper

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

arXiv:1904.01373 · doi:10.1093/pasj/psz024

Abstract

We investigate the stellar population of star-forming galaxies at $z \sim 4$ by focusing on their slope of rest-frame ultraviolet (UV) continuum, $β$ where $f_{λ} \propto λ^{β}$ . We investigate the sample of bright Lyman Break Galaxies (LBGs) with $i^{'} \leq 26.0$ in the Subaru/XMM-Newton Deep Survey field by using the SED fitting analysis. We find that the apparently redder ( $β_{obs} > - 1.73$ ) LBGs tend to be dusty ( $Av > 1.0$ ), have the young stellar population ( $β_{int} < - 2.42$ ), and the intrinsically active star-forming galaxies (SFR $≳$ a few $\times 1 0^{2}$ $M_{⊙} y r^{- 1}$ ). It means that a significant fraction of the UV-selected LBGs at $z \sim 4$ is on-going active and dust obscured star-forming galaxies. We compare the IR to UV luminosity ratio assuming the dust attenuation laws with the sub-millimeter observations from previous works. The result suggests that the Calzetti-like dust attenuation law is preferable for the active and dusty star-forming LBGs at $z = 4$ . We also find that an extrapolation of the $β_{int}$ - $M_{UV, int}$ relation toward the fainter magnitude range below our sample magnitude limit intersects the $β_{obs}$ - $M_{UV, obs}$ relation previously obtained in the deeper narrow-area observations at $M_{UV} = - 18.9$ and $β = - 1.94$ , which coincides with the break point of $β_{obs}$ - $M_{UV, obs}$ relation observed so far. The coincidence suggest that we see the almost dust-free population at $M_{UV, obs} ≳ - 18.9$ .

arXiv comment20 pages, 20 figures

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

Abstract

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