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Lyman Continuum Escape Fraction of Star-forming Dwarf Galaxies at z ~ 1

Rutkowski, Michael J. and Scarlata, Claudia and Haardt, Francesco and Siana, Brian and Henry, Alaina and Rafelski, Marc and Hayes, Matthew and Salvato, Mara and Pahl, Anthony J. and Mehta, Vihang and Beck, Melanie and Malkan, Matthew and Teplitz, Harry I. (2016) Lyman Continuum Escape Fraction of Star-forming Dwarf Galaxies at z ~ 1. Astrophysical Journal, 819 (1). Art. No. 81. ISSN 0004-637X.

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To date, no direct detection of Lyman continuum emission has been measured for intermediate-redshift (z ~ 1) star-forming galaxies. We combine Hubble Space Telescope grism spectroscopy with GALEX UV and ground-based optical imaging to extend the search for escaping Lyman continuum to a large (~600) sample of z ~ 1 low-mass log(M)≃ 9.3 M_☉), moderately star-forming (ψ ≾ 10M_☉ yr^(−1)) galaxies selected initially on Hα emission. The characteristic escape fraction of LyC from star-forming galaxies (SFGs) that populate this parameter space remains weakly constrained by previous surveys, but these faint (sub-Lsstarf) SFGs are assumed to play a significant role in the reionization of neutral hydrogen in the intergalactic medium (IGM) at high redshift z > 6. We do not make an unambiguous detection of escaping LyC radiation from this z ~ 1 sample, individual non-detections to constrain the absolute Lyman continuum escape fraction, f_(esc) < 2.1% (3σ). We measure an upper limit of f_(esc) < 9.6% from a sample of SFGs selected on high Hα equivalent width EW > 200Å), which are thought to be close analogs of high redshift sources of reionization. For reference, we also present an emissivity-weighted escape fraction that is useful for measuring the general contribution SFGs to the ionizing UV background. In the discussion, we consider the implications of these intermediate redshift constraints for the reionization of hydrogen in the IGM at high (z > 6) redshift. If we assume our z ~ 1 SFGs, for which we measure this emissivity-weighted f_(esc), are analogs to the high redshift sources of reionization, we find it is difficult to reconcile reionization by faint (M}_(UV) ≾-13) SFGs with a low escape fraction (f_(esc) < 3%), with constraints from independent high redshift observations. If f_(esc) evolves with redshift, reionization by SFGs may be consistent with observations from Planck.

Item Type:Article
Related URLs:
URLURL TypeDescription
Scarlata, Claudia0000-0002-9136-8876
Siana, Brian0000-0002-4935-9511
Henry, Alaina0000-0002-6586-4446
Rafelski, Marc0000-0002-9946-4731
Salvato, Mara0000-0001-7116-9303
Mehta, Vihang0000-0001-7166-6035
Malkan, Matthew0000-0001-6919-1237
Teplitz, Harry I.0000-0002-7064-5424
Additional Information:© 2016 The American Astronomical Society. Received 2015 April 18; accepted 2016 January 1; published 2016 March 1. We thank the referee, B. Robertson, for helpful comments that improved the discussion and conclusions presented in this work. We also thank S. Finkelstein for helpful discussion. M.H. acknowledges the support of the Swedish Research Council (Vetenskapsrådet), the Swedish National Space Board (SNSB), and the Knut and Alice Wallenberg Foundation. This research was supported by NASA NNX13AI55G and HST-AR Program #12821.01, using observations taken by the 3D-HST Treasury program (GO 12177 & 12328) with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. GALEX and HST data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) maintained by the STScI. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This research has made use of NASA's Astrophysics Data System Bibliographic Services.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Swedish Research Council (Vetenskapsrådet)UNSPECIFIED
Swedish National Space Board (SNSB)UNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
Subject Keywords:galaxies: dwarf; galaxies: starburst; galaxies: star formation; ultraviolet: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20160418-093607896
Persistent URL:
Official Citation:Michael J. Rutkowski et al 2016 ApJ 819 81
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66237
Deposited By: Ruth Sustaita
Deposited On:18 Apr 2016 19:30
Last Modified:03 Oct 2019 09:54

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