TY - JOUR

T1 - Galaxy morphologies revealed with Subaru HSC and super-resolution techniques. I. Major merger fractions of LUV∼3-15 L∗UVdropout galaxies at z ∼4-7

AU - Shibuya, Takatoshi

AU - Miura, Noriaki

AU - Iwadate, Kenji

AU - Fujimoto, Seiji

AU - Harikane, Yuichi

AU - Toba, Yoshiki

AU - Umayahara, Takuya

AU - Ito, Yohito

N1 - Funding Information: We thank Akio K. Inoue, Yuki Isobe, Ken Mawatari, Yoshiaki Ono, Marcin Sawicki, Aswin P. Vijayan, Gordon Wetzstein, and the anonymous referee for valuable comments and suggestions that have improved our paper. This work was supported by JSPS KAKENHI Grant Number 20K14508. The Cosmic Dawn Center is funded by the Danish National Research Foundation under grant No. 140. S.F. acknowledges support from the European Research Council (ERC) Consolidator Grant funding scheme (project ConTExt, grant No. 648179). This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sk?odowska-Curie grant agreement No. 847523 'INTERACTIONS'. Publisher Copyright: © 2022 The Author(s).

PY - 2022/2/15

Y1 - 2022/2/15

N2 - We perform a super-resolution analysis of the Subaru Hyper Suprime-Cam (HSC) images to estimate the major merger fractions of z ∼4-7 dropout galaxies at the bright end of galaxy UV luminosity functions (LFs). Our super-resolution technique improves the spatial resolution of the ground-based HSC images, from ∼1″ to ≲ 0″1, which is comparable to that of the Hubble Space Telescope, allowing us to identify z ∼4-7 bright major mergers at a high completeness value of ≳. We apply the super-resolution technique to 6412, 16, 94, and 13 very bright dropout galaxies at z ∼4, 5, 6, and 7, respectively, in a UV luminosity range of LUV ∼3-15, LUV∗ corresponding to -24 ≲ MUV ≲ -22. The major merger fractions are estimated to be fmerger ∼ 10%-20% at z ∼4 and ∼ 50%-70% at z ∼5-7, which shows no fmerger difference compared to those of a control faint galaxy sample. Based on the fmerger estimates, we verify contributions of source blending effects and major mergers to the bright-end of double power-law (DPL) shape of z ∼4-7 galaxy UV LFs. While these two effects partly explain the DPL shape at LUV ∼3-10, LUV∗, the DPL shape cannot be explained at the very bright end of LUV ≳ 10 LUV∗, even after the AGN contribution is subtracted. The results support scenarios in which other additional mechanisms such as insignificant mass quenching and low dust obscuration contribute to the DPL shape of galaxy UV LFs.

AB - We perform a super-resolution analysis of the Subaru Hyper Suprime-Cam (HSC) images to estimate the major merger fractions of z ∼4-7 dropout galaxies at the bright end of galaxy UV luminosity functions (LFs). Our super-resolution technique improves the spatial resolution of the ground-based HSC images, from ∼1″ to ≲ 0″1, which is comparable to that of the Hubble Space Telescope, allowing us to identify z ∼4-7 bright major mergers at a high completeness value of ≳. We apply the super-resolution technique to 6412, 16, 94, and 13 very bright dropout galaxies at z ∼4, 5, 6, and 7, respectively, in a UV luminosity range of LUV ∼3-15, LUV∗ corresponding to -24 ≲ MUV ≲ -22. The major merger fractions are estimated to be fmerger ∼ 10%-20% at z ∼4 and ∼ 50%-70% at z ∼5-7, which shows no fmerger difference compared to those of a control faint galaxy sample. Based on the fmerger estimates, we verify contributions of source blending effects and major mergers to the bright-end of double power-law (DPL) shape of z ∼4-7 galaxy UV LFs. While these two effects partly explain the DPL shape at LUV ∼3-10, LUV∗, the DPL shape cannot be explained at the very bright end of LUV ≳ 10 LUV∗, even after the AGN contribution is subtracted. The results support scenarios in which other additional mechanisms such as insignificant mass quenching and low dust obscuration contribute to the DPL shape of galaxy UV LFs.

KW - galaxies: evolution

KW - galaxies: formation

KW - galaxies: high-redshift

KW - galaxies: structure

U2 - 10.1093/pasj/psab111

DO - 10.1093/pasj/psab111

M3 - Journal article

AN - SCOPUS:85126760993

VL - 74

SP - 73

EP - 91

JO - Publication of the Astronomical Society of Japan

JF - Publication of the Astronomical Society of Japan

SN - 0004-6264

IS - 1

ER -