Beliebiger Eintrag,
The most metal-poor damped Lyman alpha systems: An insight into dwarf galaxies at high redshift
(2014)cite arxiv:1406.7003Comment: 18 pages, 8 figures, Submitted to the Astrophysical Journal.
Zusammenfassung
In this paper, we analyze the kinematics, chemistry, and physical properties
of a sample of the most metal-poor damped Lyman alpha systems (DLAs), to
uncover their links to modern-day galaxies. We present evidence that the DLA
population as a whole exhibits a `knee' in the relative abundances of the
alpha-capture and Fe-peak elements when the metallicity is Fe/H ~ -2.0. In
this respect, the chemical evolution of DLAs is clearly different from that
experienced by Milky Way halo stars, but resembles that of dwarf spheroidal
galaxies in the Local Group. We also find a close correspondence between the
kinematics of Local Group dwarf galaxies and of high redshift metal-poor DLAs,
which further strengthens this connection. On the basis of such similarities,
we propose that the most metal-poor DLAs provide us with a unique opportunity
to directly study the dwarf galaxy population more than ten billion years in
the past, at a time when many dwarf galaxies were forming the bulk of their
stars. To this end, we have measured some of the key physical properties of the
DLA gas, including their neutral gas mass, size, kinetic temperature, density,
and turbulence. We find that metal-poor DLAs mostly consist of a warm neutral
medium with T_gas ~ 9600 K predominantly held up by thermal pressure.
Furthermore, all of the DLAs in our sample exhibit a subsonic turbulent Mach
number, implying that the gas distribution is largely smooth. These results are
among the first empirical descriptions of the environments where the first few
generations of stars may have formed in our Universe.
