Large-scale bias and the peak background split

Dark matter haloes are biased tracers of the underlying dark matter distrib ution. We use a simple model to provide a relation between the abundance of dark matter haloes and their spatial distribution on large scales. Our mod el shows that knowledge of the unconditional mass function alone is suffici ent to provide an accurate estimate of the large-scale bias factor. We then use the mass function measured in numerical simulations of SCDM, OCDM and Lambda CDM to compute this bias. Comparison with these simulations shows th at this simple way of estimating the bias relation and its evolution is acc urate for less massive haloes as well as massive ones. In particular, we sh ow that haloes that are less/more massive than typical M* haloes at the tim e they form are more/less strongly clustered than is predicted by formulae based on the standard Press-Schechter mass function.