PDA

View Full Version : Least metallic nearby galaxies



chornedsnorkack
2010-Apr-11, 09:17 PM
In Milky Way, the low metallicity subdwarfs are normally old red or yellow dwarfs of red giants. Molecular gas clouds and young stars are normally metal rich.

Magellanic Clouds are noted for having lots of gas, and young globular clusters. But gas and young stars, particularly in the Small Magellanic Cloud, are noted for being less metallic than Milky Way.

Are there any other nearby galaxies, within first hundred million lightyears, that have gas and young stars and are noted for being even less metallic than Small Magellanic Cloud?

Romanus
2010-Apr-12, 02:41 AM
I honestly think that most, if not all the smaller galaxies in the Local Group outside of M31 and M33 have lower (sometimes much lower) metallicities than the Milky Way, and even the Magellanic Clouds; both the WLM Galaxy and the SagDIG are gas-rich but metal-poor.

ngc3314
2010-Apr-12, 03:39 AM
The record holder for a couple of decades has been I Zw 18, with O/H (in the ionized-gas region around its current starburst) about 1/50 solar. It is a point remarked several times that there are no galaxies with gas-phase metallicity measured to be remotely as low as the extreme Pop II stars in the Milky Way. This is in part explained by the quick enrichment in star-forming regions as massive stars start spreading nuclear products, galaxies massive enough to hold on to much of the SN ejecta will reach SMC abundances quickly in the gas phase. (This makes dwarfs a very attractive environment to form the most metal-poor stars).