1,046 research outputs found
Advances on GRB as cosmological tools
Several interesting correlations among Gamma Ray Bursts (GRB) prompt and
afterglow properties have been found in the recent years. Some of these
correlations have been proposed also to standardize GRB energetics to use them
as standard candles in constraining the expansion history of the universe up to
z>6. However, given the still unexplained nature of most of these correlations,
only the less scattered correlations can be used for constraining the
cosmological parameters. The updated E_peak-E_gamma correlation is presented.
Caveats of alternative methods of standardizing GRB energetics are discussed.Comment: 8 parges, AIP conf. proc. "Probing stellar populations out to the
distant universe, Cefalu' 2008" Vol. 1111, pp. 579-58
Unsolved Problems about Supernovae
A number of unsolved problems and open questions about the nature and the
properties of supernovae are identified and briefly discussed. Some suggestions
and directions toward possible solutions are also considered.Comment: 7 pages, Proceedings of 'Probing Stellar Populations out to the
Distant Universe', Cefalu, Italy, Sep 7-19, 2008, AIP Conf. Proc. Serie
The formation and evolution of early-type galaxies : solid results and open questions
The most recent results and some of the open key questions on the evolution
of early-type galaxies are reviewed in the general cosmological context of
massive galaxy formation.Comment: 8 pages, invited review at the workshop "Probing Stellar Populations
out to the Distant Universe", Cefalu` (Italy), September 7 - 19, 200
Spectral libraries and their uncertainties
Libraries of stellar spectra are fundamental tools in the study of stellar
populations and in automatic determination of atmospheric parameters for large
samples of observed stars. In the context of the present volume, here I give an
overview of the current status of stellar spectral libraries from the
perspective of stellar population modeling: what we have currently available,
how good they are, and where we need further improvement
Early metal enrichment in high-redshift quasars
Quasars are powerful systems whose spectrum is rich of metal features that
allow us to investigate the chemical evolution of galaxies at very high
redshift, even close to the reionization epoch. I review the main observational
constraints on the metallicity of quasars host galaxies at high redshift and
discuss the implications and issues for models of galaxy evolution in the early
universe.Comment: 8 pages, invited review at the workshop "Probing Stellar Populations
out to the Distant Universe
The cannonball model of long GRBs - overview
During the past ten years, the predictions of the cannonball (CB) model of
gamma ray bursts (GRBs) were repeatedly confronted with the mounting data from
space- and ground-based observations of GRBs and their afterglows (AGs). The
two underlying radiation mechanisms of the model, inverse Compton scattering
(ICS) and synchrotron radiation (SR), provided an accurate description of the
prompt and afterglow emission in all of the many well-sampled GRBs that were
studied. Simple as they are, these two mechanisms and the burst environment
were shown to generate the observed rich structure of the GRB light-curves at
all observed frequencies and times.Comment: Invited talk, to be published in the proceedings of Cefalu 2009
workshop `Probing stellar populations out to the distant universe', Cefalu,
Sicily, Italy, September 7-19, 200
Disentangling age and metallicity in distant unresolved stellar systems
We present some results of an observational and theoretical study on
unresolved stellar systems based on the Surface Brightness Fluctuations (SBF)
technique. It is shown that SBF magnitudes are a valuable tracer of stellar
population properties, and a reliable distance indicator. SBF magnitudes,
SBF-colors, and SBF-gradients can help to constrain within relatively narrow
limits the metallicity and age of the dominant stellar component in distant
stellar systems, especially if coupled with other spectro-photometric
indicators.Comment: A contributed paper to the Cefalu' (Italy) "Probing Stellar
Populations out to the Distant Universe", 4 pages. To appear as an AIP
Conference Proceedin
The End of Amnesia: Measuring the Metallicities of Type Ia SN Progenitors with Manganese Lines in Supernova Remnants
The Mn to Cr mass ratio in supernova ejecta has recently been proposed as a
tracer of Type Ia SN progenitor metallicity. We review the advantages and
problems of this observable quantity, and discuss them in the framework of the
Tycho Supernova Remnant. The fluxes of the Mn and Cr Kalpha lines in the X-ray
spectra of Tycho observed by the Suzaku satellite suggests a progenitor of
supersolar metallicity.Comment: 4 pages, 1 figure, Proceedings of 'Probing Stellar Populations out to
the Distant Universe'. September 15-19 2008, Cefalu, Sicily, Ital
The present-day galaxy population in spiral galaxies
Although there are many more stellar population studies of elliptical and
lenticular galaxies, studies of spiral galaxies are catching up, due to higher
signal to noise data on one hand, and better analysis methods on the other.
Here I start by discussing some modern methods of analyzing integrated spectra
of spiral galaxies, and comparing them with traditional methods. I then discuss
some recent developments in our understanding of the stellar content of spiral
galaxies, and their associated dust content. I discuss star formation
histories, radial stellar population gradients, and stellar populations in
sigma drops.Comment: 8 pages, Proceedings of 'Probing Stellar Populations out to the
Distant Universe', Cefalu, Italy, Sep 7-19, 2008, AIP Conf. Proc. Series.
Higher resolution version available at
http://www.astro.rug.nl/~peletier/rfpcefalu.pd
Ultraviolet Spectra of Local Galaxies and their Link with the High-z Population
The new generation of 8 to 10m class telescope is providing us with
high-quality spectral information on the rest-frame ultraviolet region of
star-forming galaxies at cosmological distances. The data can be used to
address questions such as, e.g., the star-formation histories, the stellar
initial mass function, the dust properties, and the energetics and chemistry of
the interstellar medium. We can tackle these issues from a different angle by
comparing the spectral properties of high-redshift galaxies to those of their
counterparts in the local universe. I give a review of recent developments
related to observations and empirical modeling of the ultraviolet spectra of
local galaxies with recent star formation. The emphasis is on the youngest
stellar populations with ages less than 100 Myr. Current uncertainties will be
discussed, and areas where progress is needed in the future are highlighted.Comment: 8 pages, invited talk given at the conference "Probing Stellar
Populations out to the Distant Universe", Cefalu (Italy), September 7 - 19,
2008. To be published in the AIP Conf. Proc. Serie
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