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

PASJ: Publications of the Astronomical Society of Japan

Yamanaka, Satoshi¹  Yamada, Toru² 

[1] Department of Environmental Science and Technology, Faculty of Design Technology, Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 574-8530, Japan;National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

关键词: galaxies: starburst;    galaxies: formation;    galaxies: evolution;    galaxies: high-redshift;   

DOI  :  10.1093/pasj/psz024

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

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 ∝ 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 |$\times \ 10^{2}\, {M_{\odot }}\:\mbox{yr}^{-1}$|⁠). 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.

【 授权许可】

CC BY