A Solution to the Missing Link in the Press‐Schechter Formalism

Abstract

The Press-Schechter (PS) formalism for mass functions of the gravitationally collapsed objects is reanalyzed. It has been suggested by many authors that the PS mass function agrees well with the mass function given by N-body simulations, while many too simple assumptions are contained in the formalism. In order to understand why the PS formalism works well, we consider the following three effects on the mass function: the filtering effect of the density fluctuation field, the peak Ansatz in which objects collapse around density maxima, and the spatial correlation of density contrasts within the region of a collapsing halo because objects have nonzero finite volume. According to the method given by Yano, Nagashima, & Gouda (YNG), who used an integral formula proposed by Jedamzik, we resolve the missing link in the PS formalism, taking into account the three effects. While YNG showed that the effect of the spatial correlation alters the original PS mass function, in this paper we show that the filtering effect almost cancels out the effect of the spatial correlation and that the original PS is almost recovered by combining these two effects, particularly in the case of the top-hat filter. On the other hand, as for the peak Ansatz, the resultant mass functions are changed dramatically and not in agreement, especially at low-mass tails in the cases of Gaussian and sharp k-space filters. We show that these properties of the mass function can be interpreted in terms of the kernel probability P(M1|M2) in the integral formula qualitatively.