Valerji Kravtsov : Globular Cluster and Super Star Cluster Formation: Some Implication for Galaxy Evolution

Peak metallicities of populations of metal-rich globular clusters (MRGCs) belonging to early-type galaxies and spheroidal
subsystems of spiral galaxies (spheroids) fall within fairly narrow range around [Fe/H]~-0.5. Irregular galaxies such as the LMC,
with longer timescales of their formation and lower star formation (SF) efficiency are observed to form populations of so called
super star clusters (SSCs) with masses > 104 M_solar. Their formation is widely believed to be an accidental process fully
dependent on external factors. However, their most probable mean metallicity, as available data show, is close to Z_solar/3 in
irregular galaxies like LMC and it is surprisingly very close to [Fe/H]=-0.5 in LMC itself. Moreover, metallicity distribution
function of stars in the LMC and in the halos of massive spheroids exhibit a significant increase toward [Fe/H]~-0.5. The
formation of both the old MRGCs in spheroids and SSC populations in irregular galaxies is suggested to occur at approximately
the same stage of the host galaxies’ chemical evolution and is related to the essentially increased SF activity in the hosts around
the same metallicity that is achieved very early in massive, later in lower mass spheroids, and much later in irregular galaxies.

Lugar :
Instituto de Astronomia

Martes 12 de Noviembre 2013

14:30 horas