The Host Haloes of Lyman Break Galaxies and Sub-millimeter 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 of the host haloes of LBGs from below, while the observed star-formation distribution constrains the masses from above. Assuming a flat CDM model with a cosmological constant ($Ω_Λ=0.7$), we find that consistency with observations requires the circular velocities of LBG host haloes to be in the range 100--$300 {\rm km s^{-1}}$. The predicted comoving correlation length of these objects is $\sim 3 h^{-1}{\rm Mpc}$, and the predicted velocity dispersion of their stellar contents is typically $70 {\rm km s^{-1}}$. The same prescription applied to larger haloes in the CDM cosmogony predicts the existence of galaxies with star formation rates $\sim 1000 {\rm M_\odot yr^{-1}}$ at redshift $z\sim 3$. We explore the possibility of identifying these galaxies to be the bright sub-millimeter (sub-mm) sources detected by SCUBA. The model predicts that the host haloes of these sub-mm sources are massive. These galaxies are predicted to be strongly correlated, with a comoving correlation length of $\sim 7 h^{-1}{\rm Mpc}$. The descendants of the bright sub-mm sources should reside in clusters of galaxies at the present time, and it is likely that these objects are the progenitors of giant ellipticals. The model predicts the existence of a relatively bright and red population of galaxies at $z\sim 3$, which may be observed in the K-band.