Abstract
We study the UV luminosity functions (LFs) at $z4$, $5$, $6,$ and $7$
based on the deep large-area optical images taken by the Hyper Suprime-Cam
(HSC) Subaru strategic program (SSP). On the 100 deg$^2$ sky of the HSC SSP
data available to date, we make enormous samples consisting of a total of
579,555 dropout candidates at $z4-7$ by the standard color selection
technique, 348 out of which are spectroscopically confirmed by our follow-up
spectroscopy and the other studies. We obtain the UV LFs at $z 4-7$ that
span a very wide UV luminosity range of $0.002 - 100 \, L_UV^\ast$
($-26 < M_UV < -14$ mag), combining UV LFs of our program and the
ultra-deep Hubble Space Telescope legacy surveys. We derive three parameters of
the best-fit Schechter function, $\phi^\ast$, $M_UV^\ast$, and $\alpha$,
of the UV LFs in the magnitude range where the AGN contribution is negligible,
and find that $\alpha$ and $\phi^\ast$ decrease from $z4$ to $7$ with no
significant evolution of $M_UV^\ast$. Because our HSC SSP data bridge the
LFs of galaxies and AGNs with great statistical accuracies, we carefully
investigate the bright ends of the galaxy UV LFs that are estimated by the
subtraction of the AGN contribution either with the spectroscopy results or the
best-fit AGN UV LFs. We find that the bright ends of the galaxy UV LFs cannot
be explained by the Schechter function fits at $> 2 \sigma$ significance, and
require either double power-law functions or modified Schechter functions
considering the gravitational lensing magnification bias.
Description
[1704.06004] Great Optically Luminous Dropout Research Using Subaru HSC (GOLDRUSH). I. UV Luminosity Functions at $z \sim 4-7$ Derived with the Half-Million Dropouts on the 100 deg$^2$ Sky
Links and resources
Tags