Powering reionization: assessing the galaxy ionizing photon budget at z < 10
Abstract
We present a new analysis of the ionizing emissivity (dot{N}_{ion}, s-1 Mpc-3) for galaxies during the epoch of reionization and their potential for completing and maintaining reionization. We use extensive spectral energy distribution modelling - incorporating two plausible mechanisms for the escape of Lyman continuum photon - to explore the range and evolution of ionizing efficiencies consistent with new results on galaxy colours (β) during this epoch. We estimate dot{N}_{ion} for the latest observations of the luminosity and star formation rate density at z < 10, outlining the range of emissivity histories consistent with our new model. Given the growing observational evidence for a UV colour-magnitude relation in high-redshift galaxies, we find that for any plausible evolution in galaxy properties, red (brighter) galaxies are less efficient at producing ionizing photons than their blue (fainter) counterparts. The assumption of a redshift and luminosity evolution in β leads to two important conclusions. First, the ionizing efficiency of galaxies naturally increases with redshift. Secondly, for a luminosity-dependent ionizing efficiency, we find that galaxies down to a rest-frame magnitude of MUV ≈ -15 alone can potentially produce sufficient numbers of ionizing photons to maintain reionization as early as z ∼ 8 for a clumping factor of C_{H II} ≤ 3.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2015
- DOI:
- 10.1093/mnras/stv1049
- arXiv:
- arXiv:1505.01846
- Bibcode:
- 2015MNRAS.451.2030D
- Keywords:
-
- galaxies: evolution;
- galaxies: high-redshift;
- galaxies: luminosity function;
- mass function;
- dark ages;
- reionization;
- first stars;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted for publication in MNRAS