A measurement of galaxy halo mass from the surrounding HI Ly{\alpha} absorption

TL;DR

This study estimates the dark matter halo masses of z~2.36 star-forming galaxies by analyzing HI Lyα absorption in QSO spectra, confirming the method's robustness and revealing gas infall signatures.

Contribution

It introduces a novel absorption-based technique to measure galaxy halo masses applicable to narrow field surveys, validated against simulations and unaffected by certain cosmological variations.

Findings

Minimum halo mass of log10(Mmin/Msun)=11.6 with uncertainties

Method's insensitivity to cosmological parameters and AGN feedback

Detection of anisotropic absorption consistent with gas infall

Abstract

We measure the dark matter halo masses of z~2.36 UV color-selected star-forming galaxies by matching the observed median HI Ly{\alpha} absorption around them, as observed in the spectra of background QSOs, to the absorption around haloes above a given mass in cosmological simulations. Focusing on transverse separations 0-2 pMpc and line of sight separations 154-616 km/s, we find a minimum halo mass of log10(Mmin/Msun)=11.6(+0.2)(-0.2), which is in good agreement with published halo mass estimates from clustering analyses. We verified that the measured halo mass is insensitive to a change in the cosmological parameters (WMAP1 vs. WMAP3) and to the inclusion of strong AGN feedback. One unique strength of this method is that it can be used in narrow field galaxy-QSO surveys, i.e. ~30 x 30 arcseconds. In addition, we find that the observed anisotropy in the 2-D HI Ly{\alpha} absorption distribution on scales of 1.5-2 pMpc is consistent with being a consequence of large-scale gas infall into the potential wells occupied by galaxies.