BRIGHT AND FAINT ENDS OF Lyα LUMINOSITY FUNCTIONS AT z = 2 DETERMINED BY THE SUBARU SURVEY: IMPLICATIONS FOR AGNs, MAGNIFICATION BIAS, AND ISM H I EVOLUTION

2015/12/31 by Akira Konno, Masami Ouchi, Kimihiko Nakajima +4
Physics and Astronomy · #Active galactic nucleus #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Erg #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Luminosity function #Magnification #Magnitude (astronomy) #Range (aeronautics) #Subaru Telescope #astro-ph.CO #astro-ph.GA

paper · pdf · doi:10.3847/0004-637x/823/1/20

18 pages, 10 figures, 5 tables, Accepted for publication in The Astrophysical Journal

arxiv created 2016/03/18 · openalex publication_date 2016/05/17 · arxiv updated 2016/05/25 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06

Abstract

ABSTRACT We present the Ly α luminosity functions (LFs) derived by our deep Subaru narrowband survey that identifies a total of 3137 Ly α emitters (LAEs) at z = 2.2 in five independent blank fields. This sample of LAEs is the largest to date and covers a very wide Ly α luminosity range of erg s −1 . We determine the Ly α LF at z = 2.2 with unprecedented accuracy and obtain the best-fit Schechter parameters of erg s −1 , Mpc −3 , and , showing a steep faint-end slope. We identify a significant hump at the LF bright end ( erg s −1 ). Because all of the LAEs in the bright-end hump have a bright counterpart(s) in either the X-ray, UV, or radio data, this bright-end hump is not made by gravitational lensing magnification bias but by active galactic nuclei (AGNs). These AGNs allow us to derive the AGN UV LF at z ∼ 2 down to the faint magnitude limit of M UV ≃ −22.5 and to constrain the faint-end slope of the AGN UV LF, α AGN = −1.2 ± 0.1, which is flatter than those at z > 4. Based on the Ly α and UV LFs from our and previous studies, we find an increase of Ly α escape fraction from z ∼ 0 to 6 by two orders of magnitude. This large increase can be explained neither by the evolution of stellar population nor by outflow alone, but by the evolution of neutral hydrogen H i density in the interstellar medium that enhances dust attenuation for Ly α by resonance scattering. Our uniform expanding shell models suggest that the typical H i column density decreases from ( z ∼ 0) to ∼1 × 10 18 cm −2 ( z ∼ 6) to explain the large increase.

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