Origin of Quasar Progenitors from the Collapse of Low-Spin Cosmological Perturbations

Abstract

We show that seeds for quasar black holes could have originated from the initial cosmological collapse of overdense regions with unusually small rotation. The gas in these rare regions collapses into a compact disk that shrinks on a short viscous time scale. Using an analytical model, we calculate the low-spin tail of the probability distribution of angular momenta for objects that collapse out of a Gaussian random field of initial density perturbations. The population of low-spin systems is significant for any viable power spectrum of primordial density perturbations. Most objects form just above the cosmological Jeans mass (\sim 10^5 M_sun) at high redshifts z>10. In the standard cold dark matter cosmology, the comoving density of 10^{6-7} M_sun objects with viscous evolution times shorter than 10^{6-7} years is about 10^{-3} (h/0.5)^3 Mpc^{-3}, comparable to the local density of bright galaxies. The seed black holes tend to reside within larger mass systems that collapse later and supply the gas needed for the bright quasar activity.