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Title: What is the physical origin of strong Lyα emission? II. Gas kinematics and distribution of Lyα emitters

We present a statistical study of velocities of Lyα, interstellar (IS) absorption, and nebular lines and gas covering fraction for Lyα emitters (LAEs) at z ≅ 2. We make a sample of 22 LAEs with a large Lyα equivalent width (EW) of ≳ 50 Å based on our deep Keck/Low Resolution Imaging Spectrometer (LRIS) observations, in conjunction with spectroscopic data from the Subaru/Fiber Multi Object Spectrograph program and the literature. We estimate the average velocity offset of Lyα from a systemic redshift determined with nebular lines to be Δv {sub Lyα} = 234 ± 9 km s{sup –1}. Using a Kolmogorov-Smirnov test, we confirm the previous claim of Hashimoto et al. that the average Δv {sub Lyα} of LAEs is smaller than that of Lyman break galaxies (LBGs). Our LRIS data successfully identify blueshifted multiple IS absorption lines in the UV continua of four LAEs on an individual basis. The average velocity offset of IS absorption lines from a systemic redshift is Δv {sub IS} = 204 ± 27 km s{sup –1}, indicating LAEs' gas outflow with a velocity comparable to typical LBGs. Thus, the ratio R{sub IS}{sup Lyα}≡Δv{sub Lyα}/Δv{sub IS} of LAEs is around unity, suggestive of low impactsmore » on Lyα transmission by resonant scattering of neutral hydrogen in the IS medium. We find an anti-correlation between Lyα EW and the covering fraction, f{sub c} , estimated from the depth of absorption lines, where f{sub c} is an indicator of average neutral hydrogen column density, N {sub H} {sub I}. The results of our study support the idea that N {sub H} {sub I} is a key quantity determining Lyα emissivity.« less
Authors:
; ;  [1] ; ; ; ;  [2] ;  [3] ;  [4] ; ;  [5]
  1. Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan)
  2. Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan)
  3. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
  4. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States)
  5. Center for Computational Sciences, The University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)
Publication Date:
OSTI Identifier:
22356662
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; CORRELATIONS; COSMOLOGY; DISTRIBUTION; EMISSION; EMISSIVITY; GALAXIES; HYDROGEN; LYMAN LINES; RED SHIFT; RESOLUTION; RESONANCE SCATTERING; SPECTROMETERS; TRANSMISSION; UNIVERSE