Formation Efficiencies of Old Globular Clusters – form Dwarf to Giant Galaxies

Abstract

For the full galaxy mass range, we find that previously observed trends of globular cluster (GC) system scaling parameters (number, luminosity or mass of all GCs in a galaxy normalized to the host galaxy luminosity or mass, e.g. SL) as a function of galaxy mass, holds irrespective of galaxy type or environment. The SL value of early-type galaxies is, on average, twice that of late-types. We derive theoretical predictions which describe remarkably well the observed GC system scaling parameter distributions given an assumed GC formation efficiency (η), i.e. the ratio of total mass in GCs to galaxy halo mass. It has a mean value of η ≃ 5.5 × 10−5, and increasing scatter toward low galaxy mass. The excess η-values of some massive galaxies compared to expectations from the mean model prediction, may be attributed to an efficient GC formation, inefficient production of field stars, accretion of low-mass high-η galaxies or likely a mixture of all these effects.