Steep faint-end slopes of galaxy mass and luminosity functions at z≥ 6 and the implications for reionization
Abstract
We present the results of a numerical study comparing photometric and physical properties of simulated z= 6-9 galaxies to the observations taken by the Wide Field Camera 3 instrument aboard the Hubble Space Telescope. Using cosmological hydrodynamical simulations we find good agreement with observations in colour-colour space at all studied redshifts. We also find good agreement between observations and our Schechter luminosity function fit in the observable range, Muv≤-18, provided that a moderate dust extinction effect exists for massive galaxies. However beyond what currently can be observed, simulations predict a very large number of low-mass galaxies and evolving steep faint-end slopes from αL=-2.15 at z= 6 to αL=-2.64 at z= 9, with a dependence of |αL| ∝ (1 +z)0.59. During the same epoch, the normalization ϕ* increases and the characteristic magnitude ? becomes moderately brighter with decreasing redshift. We find similar trends for galaxy stellar mass function with evolving low-mass end slope from αM=-2.26 at z= 6 to αM=-2.87 at z= 9, with a dependence of |αM| ∝ (1 +z)0.65. Together with our recent result on the high escape fraction of ionizing photons for low-mass galaxies, our results suggest that the low-mass galaxies are important contributor of ionizing photons for the reionization of the Universe at z≥ 6.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2012
- DOI:
- 10.1111/j.1365-2966.2011.20150.x
- arXiv:
- arXiv:1104.2345
- Bibcode:
- 2012MNRAS.420.1606J
- Keywords:
-
- methods: numerical;
- galaxies: evolution;
- galaxies: formation;
- cosmology: theory;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Revised metadata, 16 pages, 5 tables, 17 figures. MNRAS, in press