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Dissection of Hα Emitters: Low-z Analogs of z > 4 Star-forming Galaxies

Shim, Hyunjin and Chary, Ranga-Ram (2013) Dissection of Hα Emitters: Low-z Analogs of z > 4 Star-forming Galaxies. Astrophysical Journal, 765 (1). Art. No. 26. ISSN 0004-637X. doi:10.1088/0004-637X/765/1/26.

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Strong Hα emitters (HAEs) dominate the z ~ 4 Lyman-break galaxy (LBG) population. We have identified local analogs of these HAEs using the Sloan Digital Sky Survey. At z < 0.4, only 0.04% of the galaxies are classified as HAEs with Hα equivalent widths (≳500 Å) comparable to that of z ~ 4 HAEs. Local HAEs have lower stellar mass and lower ultraviolet (UV) luminosity than z ~ 4 HAEs, yet the Hα-to-UV luminosity ratio, as well as their specific star formation rate, is consistent with that of z ~ 4 HAEs, indicating that they are scaled-down versions of high-z star-forming galaxies. Compared to the previously studied local analogs of LBGs selected using rest-frame UV properties, local HAEs show similar UV luminosity surface density, weaker D_n (4000) break, lower metallicity, and lower stellar mass. This implies that the local HAEs are less evolved galaxies than the traditional Lyman break analogs. In the stacked spectrum, local HAEs show a significant He II λ4686 emission line suggesting a population of hot, massive stars similar to that seen in some Wolf-Rayet galaxies. Low [N II]/[O III] line flux ratios imply that local HAEs are inconsistent with being systems that host bright active galactic nuclei. Instead, it is highly likely that local HAEs are galaxies with an elevated ionization parameter, either due to a high electron density or large escape fraction of hydrogen ionizing photons as in the case of Wolf-Rayet galaxies.

Item Type:Article
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URLURL TypeDescription
Chary, Ranga-Ram0000-0001-7583-0621
Additional Information:© 2013 American Astronomical Society. Received 2012 May 1; accepted 2013 January 3; published 2013 February 13. We thank the referee, J. Brinchmann, for his insightful comments and valuable suggestions that improved the paper. H.S. was supported by Kyungpook National University Research Fund, 2012. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Kyungpook National UniversityUNSPECIFIED
Subject Keywords:cosmology: observations; galaxies: evolution; galaxies: starburst
Issue or Number:1
Record Number:CaltechAUTHORS:20130402-100823192
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Official Citation:Dissection of Hα Emitters : Low-z Analogs of z > 4 Star-forming Galaxies Hyunjin Shim and Ranga-Ram Chary 2013 ApJ 765 26
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37715
Deposited By: Ruth Sustaita
Deposited On:02 Apr 2013 17:27
Last Modified:09 Nov 2021 23:30

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