10 research outputs found
Chemical enrichment of the intra-cluster and intergalactic medium in a hierarchical galaxy formation model
(Abridged) We use a combination of high resolution N-body simulations and
semi-analytic techniques to follow the formation, the evolution and the
chemical enrichment of cluster galaxies in a Lambda-CDM Universe. We model the
transport of metals between the stars, the cold gas in galaxies, the hot gas in
dark matter haloes, and the intergalactic gas outside virialized haloes. We
have compared three different feedback schemes. The `retention' model assumes
that material reheated by supernova explosions is able to leave the galaxy, but
not the dark matter halo. The `ejection' model assumes that this material
leaves the halo and is then re-incorporated when structure collapses on larger
scales. The `wind' model uses prescriptions that are motivated by observations
of local starburst galaxies. We require that our models reproduce the cluster
LF from the 2dF survey, the relations between stellar mass, gas mass and
metallicity inferred from new SDSS data, and the observed amount of metals in
the ICM. With suitable adjustment of the free parameters in the model, a
reasonable fit to the observational results at redshift zero can be obtained
for all three feedback schemes. All three predict that the chemical enrichment
of the ICM occurs at high redshift with 60-80 per cent of the metals currently
in the ICM ejected at redshifts larger than 1. Massive galaxies are important
contributors to the chemical pollution. The observed decline in baryon fraction
from rich clusters to galaxy groups is reproduced only in an `extreme' ejection
scheme, where material ejected from dark matter haloes is re-incorporated on a
timescale comparable to the age of the Universe. We explore how the metal
abundance in the intergalactic medium as a function of redshift can constraint
how and when galaxies ejected their metals.Comment: Accepted for publication in MNRAS. 17 pages, 13 figures. Minor
changes to submitted versio
Observations of Ly Emitters at High Redshift
In this series of lectures, I review our observational understanding of
high- Ly emitters (LAEs) and relevant scientific topics. Since the
discovery of LAEs in the late 1990s, more than ten (one) thousand(s) of LAEs
have been identified photometrically (spectroscopically) at to . These large samples of LAEs are useful to address two major astrophysical
issues, galaxy formation and cosmic reionization. Statistical studies have
revealed the general picture of LAEs' physical properties: young stellar
populations, remarkable luminosity function evolutions, compact morphologies,
highly ionized inter-stellar media (ISM) with low metal/dust contents, low
masses of dark-matter halos. Typical LAEs represent low-mass high- galaxies,
high- analogs of dwarf galaxies, some of which are thought to be candidates
of population III galaxies. These observational studies have also pinpointed
rare bright Ly sources extended over kpc, dubbed
Ly blobs, whose physical origins are under debate. LAEs are used as
probes of cosmic reionization history through the Ly damping wing
absorption given by the neutral hydrogen of the inter-galactic medium (IGM),
which complement the cosmic microwave background radiation and 21cm
observations. The low-mass and highly-ionized population of LAEs can be major
sources of cosmic reionization. The budget of ionizing photons for cosmic
reionization has been constrained, although there remain large observational
uncertainties in the parameters. Beyond galaxy formation and cosmic
reionization, several new usages of LAEs for science frontiers have been
suggested such as the distribution of {\sc Hi} gas in the circum-galactic
medium and filaments of large-scale structures. On-going programs and future
telescope projects, such as JWST, ELTs, and SKA, will push the horizons of the
science frontiers.Comment: Lecture notes for `Lyman-alpha as an Astrophysical and Cosmological
Tool', Saas-Fee Advanced Course 46. Verhamme, A., North, P., Cantalupo, S., &
Atek, H. (eds.) --- 147 pages, 103 figures. Abstract abridged. Link to the
lecture program including the video recording and ppt files :
https://obswww.unige.ch/Courses/saas-fee-2016/program.cg