Charles Jose, Kandaswamy Subramanian, Raghunathan Srianand, Saumyadip Samui
We present a physically motivated semi-analytic model to understand the clustering of high redshift LBGs. We show the model parameters constrained by the observed luminosity function of high-z LBGs can be used to predict large scale (\theta < 80 arcsec) bias and angular correlation function of galaxies. These predictions are shown to reproduce the observations remarkably well. We then adopt these model parameters to calculate the halo occupation distribution (HOD) using the conditional mass function. The halo model using this HOD is shown to provide a reasonably good fit to the observed clustering of LBGs at both large and small (\theta < 10") angular scales for z=3-5 and several limiting magnitudes. However, our models under predict the clustering at intermediate angular scales, where quasi-linear effects are important. The average mass of halos contributing to the observed clustering is 5.7x10^{11} M_\odot and the characteristic mass of a parent halo hosting satellite galaxies is 10^{12} M_\odot for M_{AB} < -20.5 at z=4. For a given threshold luminosity these masses increase with increasing z and at any given z these are found to increase with increasing value of threshold luminosity. We find that the average number of satellites in a parent halo is smaller than 1. Thus the small scale clustering detected at high-z is most likely to be dominated by LBG pairs rather than few large clusters. Large scale clustering predictions have only weak dependence on our model parameters and we may need measurements with better than 10% accuracy to constrain cosmological parameters. However, we find that the small angular scale clustering is quite sensitive to changes in the duration of star formation in a halo and hence could provide a probe of this quantity. The present data favor star formation in a halo lasting typically for a dynamical time-scale.
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http://arxiv.org/abs/1208.2097
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