Ultra-faint dwarf galaxies
DOI:
https://doi.org/10.47456/Cad.Astro.v5n1.43864Keywords:
dwarf galaxies, kinematic, dark matter, metalicity, star formationAbstract
The first ultra-faint dwarf galaxy UFD was discovered in the Sloan Digital Sky Survey (SDSS) in 2005, beginning a search that led to the discovery of several tens of similar dwarf galaxies. They are a continuation of the classical dwarf spheroidal galaxies known before SDSS towards lower luminosities and lower metallicities. The study of stellar kinematics revealed that UFD galaxies have more dark matter than the classical dwarf galaxies. Spectroscopic observations show that the stars within UFD galaxies are among the oldest and most metal-poor stars known. The abundances of iron Fe and other chemical elements show large spread due to extended star formation in the past. The analysis of individual stars in UFD galaxies in a small stellar mass interval is consistent with the hypothesis that large numbers of massive stars were formed in UFD galaxies and that the process of star formation ended at the epoch of reionization of the universe at redshift z ∼ 6. Once the UFD galaxies are the oldest and most dark matter-dominated known stellar systems, they are excellent laboratoriesto study formation of the first galaxies in the universe as well as the behaviour of dark matter on small scales.
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