505 research outputs found
The Cosmic Evolution of Gamma-Ray Burst Host Galaxies
Due to their extreme luminosities, gamma-ray bursts (GRBs) can be detected in
hostile regions of galaxies, nearby and at very high redshift, making them
important cosmological probes. The investigation of galaxies hosting
long-duration GRBs (whose progenitor is a massive star) demonstrated their
connection to star formation. Still, the link to the total galaxy population is
controversial, mainly because of the small-number statistics: ~ 1,100 are the
GRBs detected so far, ~ 280 those with measured redshift, and ~ 70 the hosts
studied in detail. These are typically low-redshift (z < 1.5), low luminosity,
metal poor, and star-forming galaxes. On the other hand, at 1.5< z <4, massive,
metal rich and dusty, interacting galaxies are not uncommon. The most distant
population (z > 4) is poorly explored, but the deep limits reached point
towards very small and star-forming objects, similar to the low-z population.
This `back to the future' behavior is a natural consequence of the connection
of long GRBs to star formation in young regions of the universe.Comment: Invited talk at the Fall 2012 Gamma-Ray Burst Symposium (Marbella,
Oct 2012), revised version after referee's report, to appear in the European
Astronomical Society Publications Serie
The Dust Depletion and Extinction of the GRB 020813 Afterglow
The Keck optical spectrum of the GRB 020813 afterglow is the best ever
obtained for GRBs. Its large spectral range and very high S/N ratio allowed for
the first time the detection of a vast variety of absorption lines, associated
with the circumburst medium or interstellar medium of the host. The remarkable
similarity of the relative abundances of 8 elements with the dust depletion
pattern seen in the Galactic ISM suggests the presence of dust. The derived
visual dust extinction A_V=0.40+/-0.06 contradicts the featureless UV spectrum
of the afterglow, very well described by a unreddened power law. The
forthcoming Swift era will open exciting opportunities to explain similar
phenomena in other GRB afterglows.Comment: To be published in "Il Nuovo Cimento", Proceedings of the 4th Rome
Workshop on Gamma-Ray Bursts in the Afterglow Era, eds. L. Piro, L. Amati, S.
Covino, B. Gendr
Swift publication statistics: a comparison with other major observatories
Swift is a satellite equipped with gamma-ray, X-ray, and optical-UV
instruments aimed at discovering, localizing and collecting data from gamma-ray
bursts (GRBs). Launched at the end of 2004, this small-size mission finds about
a hundred GRBs per year, totaling more than 700 events as of 2012. In addition
to GRBs, Swift observes other energetic events, such as AGNs, novae, and
supernovae. Here we look at its success using bibliometric tools; that is the
number of papers using Swift data and their impact (i.e., number of citations
to those papers). We derived these for the publication years 2005 to 2011, and
compared them with the same numbers for other major observatories. Swift
provided data for 1101 papers in the interval 2005-2011, with 24 in the first
year, to 287 in the last year. In 2011, Swift had more than double the number
of publications as Subaru, it overcame Gemini by a large fraction, and reached
Keck. It is getting closer to the ~400 publications of the successful
high-energy missions XMM-Newton and Chandra, but is still far from the most
productive telescopes VLT (over 500) and HST (almost 800). The overall average
number of citations per paper, as of November 2012, is 28.3, which is
comparable to the others, but lower than Keck (41.8). The science topics
covered by Swift publications have changed from the first year, when over 80%
of the papers were about GRBs, while in 2011 it was less than 30%.Comment: PASP accepted, minor changes after referee's repor
The metal absorption systems of the Hubble Deep Field South QSO
The Hubble Deep Field South (HDFS) has been recently selected and the
observations are planned for October 1998. We present a high resolution (FWHM
\kms) spectrum of the quasar J2233--606 () which
is located 5.1 arcmin East of the HDFS. The spectrum obtained with the New
Technology Telescope redward of the Lyman-- emission line covers the
spectral range 4386--8270 \AA. This range corresponds to redshift intervals for
CIV and MgII intervening systems of and
respectively. The data reveal the presence of two complex intervening CIV
systems at redshift and and two complex associated
() systems. Other two CIV systems at and
, suggested by the presence of strong Lyman-- lines in low
resolution ground based and Hubble Space Telescope (HST) STIS observations
(Sealey et al. 1998) have been identified. The system at is also
responsible for the Lyman limit absorption seen in the HST/STIS spectrum. The
main goal of the present work is to provide astronomers interested in the
Hubble Deep Field South program with information related to absorbing
structures at high redshift, which are distributed along the nearby QSO line of
sight. For this purpose, the reduced spectrum, obtained from three hours of
integration time, has been released to the astronomical community.Comment: revisited version accepted for publication by Astronomical Journal;
minor changes; typographical errors corrected; results and discussion
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