We propose a Symposium which considers low-metallicity star formation both
from a local perspective, and at high redshifts, when the first galaxies
are predicted to form. Although low-mass metal-poor galaxies in the local
universe have often been proposed as the "primordial building blocks" in the
hierarchical scenario of structure formation, several lines of evidence suggest
that this may not be true. Moreover, it is not clear to what extent dwarf
galaxies, because they are metal poor and because of their kinematics and
structure, can tell us about how star formation proceeded in the early universe.
These apparent contradictions can be better debated by bringing together
astronomers from heterogeneous fields including stellar populations and
population synthesis, stellar evolution and the end-products of star formation,
the physics and dynamics of the interstellar medium, and chemical evolution.
Combining theory of metal-poor and primordial star formation with low- and
high-redshift observations over a wide range of wavelengths from the X-ray
to the radio will allow us to assess the viability of using local dwarf
galaxies as high-redshift analogues. We aim to foster an open exchange among
different astronomical communities by placing in juxtaposition, for the first
time, low-redshift observational astronomers and observational cosmologists,
as well as observers and theoreticians.
From the local perspective, the stellar populations
and the interstellar medium (ISM)
in low-metallicity star-forming dwarf galaxies are intimately related,
but the importance of dust and molecular gas and their effect on
low-metallicity star formation are only now beginning to
be appreciated.
The mechanisms of feedback and their influence on
chemical evolution are still controversial,
even though they control the observed abundance patterns
in the metal-poor ISM.
At cosmological redshifts, recent evidence suggests that
gamma-ray bursts (GRBs)
may be hosted preferentially by metal-poor low-mass galaxies. GRBs may
help achieve a better understanding of the physics of stellar evolution in the
chemically unenriched environments of the high-redshift universe.
dust in high-redshift objects must have been created by
supernova explosions, since
there has not been sufficient time at high redshifts for dust production from
intermediate-age and evolved stars. The
metals synthesized and released in the
surrounding gas need to be transported out of the galaxies in which they are
produced into the low density regions of the
intergalactic medium (IGM) , where
they are observed up to redshifts as high as ~6.
Although metal enrichment of
the IGM has received great attention, both the nature of the sources and the
epoch where most of the pollution took place remain highly debated.
The metal enrichment
history of the gas within galaxies and in the diffuse IGM has a strong
feedback on structure formation and the nature of stellar populations.
At the highest redshifts, chemical feedback might be responsible
for the transition from very massive
Population III stars to Population II
stars spanning the conventional mass range.
Theoretical models suggest that primordial star formation and evolution is
strongly influenced by the peculiar environment in which it takes place through
a combination of
mechanical, chemical, and radiative feedback
processes whose importance is only now emerging.
These early epochs of star formation will be accessible to direct observations
with JWST. In view of this major breakthrough,
"stellar archeology" of the most metal-poor stars observed in the
Galactic halo or in nearby dwarf satellites of the Milky Way,
is already providing a powerful probe of high redshift star formation.
These together with more specific themes will be covered in the program as
outlined in Science Topics.
Our implicit assumptions are that:
- Combining low- and high-redshift observations of low-metallicity objects will
achieve a better understanding of both;
- Confronting data for low-metallicity environments with theory of how the
first stars form will provide important new insight into primordial star
formation; and
- With such an approach, we will be able to better plan for and exploit the
new observational facilities coming online in the next few years including
Herschel, ALMA, JWST, CCAT, LOFAR, and SKA.
