The host haloes of Lyman-break galaxies and submillimetre sources

Abstract

We use the observed sizes and star formation rates of Lyman-break galaxies (LBGs) to understand their properties expected in the hierarchical scenario of galaxy formation. The observed size distribution constrains the masses (or circular velocities) of the host haloes of LBGs from below, because small haloes can only host galaxies with small sizes. The observed star formation distribution constrains the masses from above, because the number density of massive haloes in duty cycle is too low to host all the observed galaxies. Assuming a flat CDM model with a cosmological constant (Omega (Lambda) = 0.7), we find that consistency with observations requires the circular velocities of LBG host haloes to be in the range 100-300 km s(-1). The star formation in these haloes is efficient; a large fraction of all the gas in them can form stars on a time-scale of about 10-20 per cent of the Hubble time at redshift of 3. The predicted comoving correlation length of these objects is similar to3 h(-1) Mpc, and the predicted velocity dispersion of their stellar contents is typically 70 km s(-1).