We investigate the nature of ultra faint dwarf spheroidal galaxies (UF dSphs) in a general cosmological context, simultaneously accounting for various "classical" dSphs and Milky Way (MW) properties, including their metallicity distribution function (MDF). Our model successfully reproduces both the observed [Fe/H]-luminosity relation and the mean MDF of UFs. According to our results, UFs are the living fossils of H-2-cooling minihalos formed at z > 8.5, i.e. before the end of reionization. They are the oldest and the most dark matter-dominated (M/L > 100) dSphs in the MW system, with total masses of M = 10(7-8)M(circle dot). The model allows us to interpret the different shapes of UF and classical dSph MDFs along with the frequency of extremely metal-poor stars in these objects. We discuss the "missing satellites problem" by comparing UF star formation efficiencies with those derived for minihalos in the Via Lactea simulation.
The faintest galaxies / Salvadori, Stefania; Ferrara, Andrea. - STAMPA. - (2010), pp. 180-183. (Intervento presentato al convegno THE FIRST STARS AND GALAXIES: CHALLENGES FOR THE NEXT DECADE) [10.1063/1.3518849].
The faintest galaxies
SALVADORI, STEFANIA;
2010
Abstract
We investigate the nature of ultra faint dwarf spheroidal galaxies (UF dSphs) in a general cosmological context, simultaneously accounting for various "classical" dSphs and Milky Way (MW) properties, including their metallicity distribution function (MDF). Our model successfully reproduces both the observed [Fe/H]-luminosity relation and the mean MDF of UFs. According to our results, UFs are the living fossils of H-2-cooling minihalos formed at z > 8.5, i.e. before the end of reionization. They are the oldest and the most dark matter-dominated (M/L > 100) dSphs in the MW system, with total masses of M = 10(7-8)M(circle dot). The model allows us to interpret the different shapes of UF and classical dSph MDFs along with the frequency of extremely metal-poor stars in these objects. We discuss the "missing satellites problem" by comparing UF star formation efficiencies with those derived for minihalos in the Via Lactea simulation.
I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
