Other
Scientific paper
Dec 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998mcdg.proc...91t&link_type=abstract
The Magellanic Clouds and Other Dwarf Galaxies, Proceedings of the Bonn/Bochum-Graduiertenkolleg Workshop, held at the Physikzen
Other
Blue Compact Dwarf Galaxies, Young Dwarf Galaxies, Helium Abundance, Metal Abundance
Scientific paper
We develop the theme that the study of extremely metal-deficient Blue Compact Dwarf (BCD) galaxies is crucial for understanding galaxy formation and evolution and constraining cosmological parameters. We discuss in detail two BCDs with a metallicity less than 1/20 that of the sun, SBS 0335-052 (Z-sun/41) and SBS 1415+437 (Z-sun/21). We show that the two BCDs do not contain stars older than 100 Myr and thus appear to be truly young galaxies, undergoing now their first burst of star formation. The H I envelope in which SBS 0335-052 is embedded appears to be primordial, devoid of any heavy element. We then discuss the chemical abundances in young dwarf galaxies and argue that all galaxies with Z <= Z-sun/20 are young, with ages not exceeding 100 Myr. We show how the study of the escape of Ly-alpha photons in BCDs can shed light on the long-standing problem of the weakness or absence of Lyα emission in high-redshift star-forming galaxies. We also discuss the P Cygni profile phenomenon in extremely metal-deficient environments. We finally give a determination of the primordial helium abundance which is higher than previous measurements and more consistent with current measurements of the abundances of other primordial elements.
Izotov Yu. I.
Thuan Trinh Xuan
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