52 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 supernova rate: a critical ingredient and an important tool
In this review I summarize the role of supernova rate as a critical
ingredient of modern astrophysics, and as an important tool to understand SN
explosions. Many years of active observations and theoretical modeling have
produced several important results. In particular, linking SN rates with parent
stellar populations has proved to be an important strategy. Despite these
advances, the situation is far from clear, in particular for the SNe Ia.Comment: 9 pages; "Probing Stellar Populations out to the Distant Universe",
Cefalu' (Italy), September 2008, AIP Conf. Proc. Series; Invited revie
Pre-metamorphic melt infiltration in metasediments : geochemical, isotopic (Sr, Nd, and Pb), and field evidence from Serie dei Laghi (Southern Alps, Italy)
Gradual transitions from K-feldspar free gneisses to K-feldspar bearing augengneisses
are sometimes observed in metamorphic terranes. They have been explained with
metasomatic porphyroblastic growth connected with regional metamorphism, or with
pre-metamorphic presence of magmatic megacrysts. A transition of this kind can be
observed in the Serie dei Laghi (Southern Alps, Italy), where coarse-grained metaarenites
(Cenerigneiss) grade into Ceneri augengneisses with large K-feldspar porphyroclasts,
and banded amphibolites of the \u2018\u2018Strona Ceneri Border Zone\u2019\u2019 grade into Hbl
augengneisses rich in K-feldspar.
The Ceneri augengneisses are chemically indistinguishable from the Cenerigneiss, but
have higher 87Sr=86Sr (0.7256\u20130.7258 vs. 0.7215\u20130.7233), similar to those of the Ordovician
granites that were intruded, before the regional metamorphism, into the protoliths
of both Cenerigneiss and amphibolites. The Cenerigneiss contains two types of zircons:
(1) highly luminescent, rounded grains or fragments, yielding U\u2013Pb SHRIMP
ages from 0.43 to 1.0 Ga; (2) euhedral grains with oscillatory zoning (magmatic), with
U\u2013Pb SHRIMP concordant ages of 466 13 Ma. This age coincides with the Rb\u2013Sr
whole rock emplacement age of the Ordovician granitoids (466 5Ma).The Hbl augengneisses form three groups with distinct geochemical patterns,
whose distributions on inter-element diagrams trend towards the Ordovician metagranites
and meta-aplites. In addition, the Hbl augengneisses have higher 87Sr=86Sr
(0.7132\u20130.7147 vs. 0.7031\u20130.7046) and lower 143Nd=144Nd (0.51214\u20130.51219 vs.
0.51273\u20130.51297) than the amphibolites, suggesting the addition of an isotopically
evolved component.
The observed chemical and isotope patterns, as well as the vicinity of the augen
gneisses to the Ordovician intrusions, lead us to conclude that the Ceneri augengneisses
and Hbl augengneisses are the result of infiltration of residual hydrous
magmas into the protolith of both the Cenerigneiss and the amphibolites at the time
of Ordovician granite emplacement, long before the regional metamorphism in the Serie dei Laghi
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