Lyman break Galaxies: Their progenitors and descendants

We study the evolution of Lyman break Galaxies (LBGs) from z = 5 to z = 0 by tracing the merger trees of galaxies in a large-scale hydrodynamic simulation based on a Lambda cold dark matter model. In particular, we emphasize the range of properties of the sample selected by rest-frame V-band luminosity, in accordance with recent near-IR observations. The predicted rest-frame V-band luminosity function agrees well with the observed one when dust extinction is taken into account. The stellar content and the star formation histories of LBGs are also studied. We find that LBGs intrinsically brighter than M-v = -21.0 at z = 3 have stellar masses of at least 10(9) M., with a median of 10(10) h(-1) M-.. The brightest LBGs (M-v less than or similar to -23) at z = 3 merge into clusters/groups of galaxies at z = 0, as suggested by clustering studies of LBGs. Roughly half the galaxies with -23 less than or similar to M-v less than or similar to -22 at z = 3 fall into groups/clusters, and the other half become typical L* galaxies at z = 0, with stellar mass of approximate to10(11) M-.. Descendants of LBGs at the present epoch have formed roughly 30% of their stellar mass by z = 3, and half their current stellar population is 10 Gyr old, favoring the scenario that LBGs are the precursors of the present-day spheroids. We find that the most luminous LBGs have undergone a starburst within 500 Myr before z = 3, but also have formed stars continuously over a period of 1 Gyr before z = 3, when all the star formation in progenitors is coadded. We also study the evolution of the mean stellar metallicity distribution of galaxies and find that the entire distribution shifts to lower metallicity at higher redshift. The observed subsolar metallicity of LBGs at z = 3 is naturally predicted in our simulation.