Lyman continuum escape fraction of star-forming dwarf galaxies at z ∼ 1
- Minnesota Institute for Astrophysics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States)
- Dipartimento di Scienza e alta Tecnologia, Università dell’Insubria, via Valleggio 11, I-22100 Como (Italy)
- Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States)
- Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)
- Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden)
- Max Planck Institut für Plasma Physik and Excellence Cluster, D-85748 Garching (Germany)
- Astronomy Division, University of California, Los Angeles, CA 90095-1562 (United States)
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-bar ) ≃ 9.3M{sub ⊙}), moderately star-forming ( Ψ-bar ≲ 10M{sub ⊙} yr{sup −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-L{sub ⋆}) 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{sub esc} < 2.1% (3σ). We measure an upper limit of f{sub esc} < 9.6% from a sample of SFGs selected on high Hα equivalent width (EW > 200 A-ring ), 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{sub esc}, are analogs to the high redshift sources of reionization, we find it is difficult to reconcile reionization by faint (M{sub UV}≲−13) SFGs with a low escape fraction (f{sub esc} < 3%), with constraints from independent high redshift observations. If f{sub esc} evolves with redshift, reionization by SFGs may be consistent with observations from Planck.
- OSTI ID:
- 22886960
- Journal Information:
- Astrophysical Journal, Vol. 819, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
Similar Records
The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%
The Lyman continuum escape fraction of the cosmic horseshoe: a test of indirect estimates