Han-Seek Kim, C. Power, C. M. Baugh, J. S. B. Wyithe, C. G. Cedric, C. D. P. Lagos, C. S. Frenk
Using the semi-analytical galaxy formation model GALFORM, we investigate the impact of feedback -- from supernovae (SNe), active galactic nuclei (AGN) and a photo-ionizing background at high redshifts -- on the neutral atomic hydrogen (HI) mass function, the corresponding bJ band luminosity function, and the spatial clustering of these galaxies at z=0. We use a version of GALFORM that calculates self-consistently the amount of HI in a galaxy as a function of cosmic time and links its star formation rate to its mass of molecular hydrogen (H2). We find that a systematic increase or decrease in the strength of SNe feedback leads to a systematic decrease or increase in the amplitudes of the luminosity and HI mass functions, but has little influence on their overall shapes. Varying the strength of AGN feedback influences only the numbers of the brightest or most HI massive galaxies, while the impact of varying the strength of photo-ionization feedback is restricted to the numbers of the faintest or least HI massive galaxies. Our results suggest that the HI mass function should provide an important limit on the minimum halo mass responsible for cosmological reionization, ruling out systems with circular velocities larger than ~50km/s. Interestingly, we find that whether a galaxy is HI-poor or HI-rich has greater influence on its clustering strength, as measured by the 2-point correlation function and the halo occupation distribution, than the strength of feedback; where feedback is effective, its influence is greatest on HI-rich systems. This suggests that environment plays a role as important as feedback in shaping the HI properties of galaxies.
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http://arxiv.org/abs/1208.2985
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