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Ultra faint dwarfs: probing early cosmic star formation

Authors :
Stefania Salvadori
Andrea Ferrara
Salvadori, S
Ferrara, Andrea
Kapteyn Astronomical Institute
Source :
Monthly Notices of the Royal Astronomical Society, 395(1), L6-L10. Oxford University Press
Publication Year :
2009

Abstract

We investigate the nature of the newly discovered Ultra Faint dwarf spheroidal galaxies (UF dSphs) in a general cosmological context simultaneously accounting for various ``classical`` dSphs and Milky Way properties including their Metallicity Distribution Function (MDF). To this aim we extend the merger tree approach previously developed to include the presence of star-forming minihaloes, and an heuristic prescription for radiative feedback. The model successfully reproduces both the observed [Fe/H]-Luminosity relation and the mean MDF of UFs. In this picture UFs are the oldest, most dark matter-dominated (M/L > 100) dSphs with a total mass M= 10^{7-8}Msun; they are leftovers of H_2-cooling minihaloes formed at z > 8.5, i.e. before reionization. Their MDF is broader (because of a more prolonged SF) and shifted towards lower [Fe/H] (as a result of a lower gas metallicity at the time of formation) than that of classical dSphs. These systems are very ineffectively star-forming, turning into stars by z=0 only<br />5 pages, 4 figures, accepted for publication in MNRAS http://saveitalianbrains.wordpress.com

Details

Language :
English
ISSN :
00358711
Database :
OpenAIRE
Journal :
Monthly Notices of the Royal Astronomical Society, 395(1), L6-L10. Oxford University Press
Accession number :
edsair.doi.dedup.....fff84ef83655bfec7ef65d46e4cb45c7