Formation and Disruption of Cosmological Low Mass Objects

We investigate the evolution of cosmological low mass (low virial temperature) objects and the formation of the first luminous objects. First, the ‘cooling diagram’ for low mass objects is shown. We assess the cooling rate taking into account the contribution of H2, which is not in chemical equilibrium generally, with a simple argument of time scales. The reaction rates and the cooling rate of H2 are taken from the recent results by Galli & Palla (1998). Using this cooling diagram, we also estimate the formation condition of luminous objects taking into account the supernova (SN) disruption of virialized clouds. We find that the mass of the first luminous object is several ×10M⊙, because smaller objects may be disrupted by the SNe before they become luminous. Metal pollution of low mass (Ly-α) clouds also discussed. The resultant metallicity of the clouds is Z/Z⊙ ∼ 10 . Subject headings: cosmology: theory — early universe — galaxies: formation — molecular processes — shock waves e-mail:[email protected] e-mail:[email protected]