Formation of globular clusters in merging galaxies

Collisions and, mergers of gas-rich galaxies trigger bursts of star and cluster formation. Of the thousands of clusters typically formed during a major merger, only the most massive and compact survive for Gigayears as globular clusters (GCs). In less than or equal to 1 Gyr old merger remnants, these 'second-generation' GCs appear by the hundreds as young halo clusters of similar tosolar metallicity. Their likely descendants, metal-rich GCs of intermediate age (2 - 5 Cyr), have recently been found in - 10 E galaxies, where they appear as slightly overluminous red GCs With a still power-law-like luminosity function. Their color and radial distributions suggest that they evolve into the red metal-rich GCs observed in old ellipticals. There is. good evidence that second-generation GCs form from giant molecular clouds shocked by the rapid pressure increase in merger-induced starbursts. This mechanism supports the view that the universal pressure increase during cosmological reionization. may have triggered the formation of the metal-poor globulars observed in galaxies of all types.