On the effect of the ionising background on the Ly{\alpha} forest autocorrelation function
Abstract
An analytical framework is presented to understand the effects of a fluctuating intensity of the cosmic ionising background on the correlations of the Ly{\alpha} forest transmission fraction measured in quasar spectra. In the absence of intensity fluctuations, the Ly{\alpha} power spectrum should have the expected cold dark matter power spectrum with redshift distortions in the linear regime, with a bias factor b_{\delta} and a redshift distortion parameter {\beta} that depend on redshift but are independent of scale. The intensity fluctuations introduce a scale dependence in both b_{\delta} and {\beta}, but keeping their product b_{\delta}{\beta} fixed. Observations of the Ly{\alpha} correlations and cross-correlations with radiation sources like those being done at present in the BOSS survey of SDSS-III (Busca et al. 2013; Slosar et al. 2013; Font-Ribera et al. 2014) have the potential to measure this scale dependence, which reflects the biasing properties of the sources and absorbers of the ionising background. We also compute a second term affecting the Ly{\alpha} spectrum, due to shot noise in the sources of radiation. This term is very large if luminous quasars are assumed to produce the ionising background and to emit isotropically with a constant luminosity, but should be reduced by a contribution from galaxies, and by the finite lifetime and anisotropic emission of quasars.
Keywords
Cite
@article{arxiv.1404.7425,
title = {On the effect of the ionising background on the Ly{\alpha} forest autocorrelation function},
author = {Satya Gontcho A Gontcho and Jordi Miralda-Escudé and Nicolás G. Busca},
journal= {arXiv preprint arXiv:1404.7425},
year = {2016}
}
Comments
12 pages, 6 figures Accepted for publication in MNRAS