Reionization and Galaxy Formation in Warm Dark Matter Cosmologies
- Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands)
- National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411007 (India)
- Department of Astronomy and Texas Cosmology Centre, University of Texas, Austin, TX 78712 (United States)
- Department of Physics, Yale University, P.O. Box 208121, New Haven, CT 06520 (United States)
We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ≃ 5–20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth (τ {sub es}) and the ionizing photon emissivity ( n-dot {sub ion}), to shed light on the reionization history and sources in Cold (CDM) and Warm Dark Matter (WDM; particle masses of m{sub x} = 1.5, 3, and 5 keV) cosmologies. This model includes all of the key processes of star formation, supernova feedback, the merger/accretion/ejection driven evolution of gas and stellar mass and the effect of the ultra-violet background (UVB), created during reionization, in photo-evaporating the gas content of galaxies in halos with M {sub h} ≲ 10{sup 9} M{sub ⊙}. We find that the delay in the start of reionization in light (1.5 keV) WDM models can be compensated by a steeper redshift evolution of the ionizing photon escape fraction and a faster mass assembly, resulting in reionization ending at comparable redshifts (z ≃ 5.5) in all the dark matter models considered. We find that the bulk of the reionization photons come from galaxies with a halo mass of M {sub h} ≲ 10{sup 9} M{sub ⊙} and a UV magnitude of −15 ≲ M {sub UV} ≲ −10 in CDM. The progressive suppression of low-mass halos with decreasing m{sub x} leads to a shift in the “reionization” population to larger halo masses of M {sub h} ≳ 10{sup 9} M{sub ⊙} and −17 ≲ M {sub UV} ≲ −13 for 1.5 keV WDM. We find that current observations of τ {sub es} and the ultra violet luminosity function are equally compatible with all the (cold and warm) dark matter models considered in this work. Quantifying the impact of the UVB on galaxy observables (luminosity functions, stellar mass densities, and stellar to halo mass ratios) for different DM models, we propose that global indicators including the redshift evolution of the stellar mass density and the stellar mass–halo mass relation, observable with the James Webb Space Telescope, can be used to distinguish between CDM and WDM (1.5 keV) cosmologies.
- OSTI ID:
- 22869427
- Journal Information:
- Astrophysical Journal, Vol. 836, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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