Publication Date:
2016-07-30
Description:
We use the Lyα Mass Association Scheme (LyMAS) to predict cross-correlations at z = 2.5 between dark matter haloes and transmitted flux in the Lyα forest, and compare to cross-correlations measured for quasars and damped Lyα systems (DLAs) from the Baryon Oscillation Spectroscopic Survey (BOSS) by Font-Ribera et al. We calibrate LyMAS using Horizon-AGN hydrodynamical cosmological simulations of a (100 h – 1 Mpc) 3 comoving volume. We apply this calibration to a (1 h – 1 Gpc) 3 simulation realized with 2048 3 dark matter particles. In the 100 h – 1 Mpc box, LyMAS reproduces the halo-flux correlations computed from the full hydrodynamic gas distribution very well. In the 1 h – 1 Gpc box, the amplitude of the large-scale cross-correlation tracks the halo bias b h as expected. We provide empirical fitting functions that describe our numerical results. In the transverse separation bins used for the BOSS analyses, LyMAS cross-correlation predictions follow linear theory accurately down to small scales. Fitting the BOSS measurements requires inclusion of random velocity errors; we find best-fitting rms velocity errors of 399 and $252\ \rm {km}\ \rm {s}^{-1}$ for quasars and DLAs, respectively. We infer bias-weighted mean halo masses of $M_{\rm h}/10^{12}\ h^{-1}\,\mathrm{M}_{\odot }=2.19^{+0.16}_{-0.15}$ and $0.69^{+0.16}_{-0.14}$ for the host haloes of quasars and DLAs, with ~0.2 dex systematic uncertainty associated with redshift evolution, intergalactic medium parameters, and selection of data fitting range.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
