87 research outputs found
An Extremely Deep Wide-Field Near-Infrared Survey: Bright Galaxy Counts and Local Large Scale Structure
We present a deep, wide-field near-infrared (NIR) survey over five widely
separated fields at high Galactic latitude covering a total of ~ 3 deg^2 in J,
H, and Ks. The deepest areas of the data (~ 0.25 deg^2) extend to a 5 sigma
limiting magnitude of JHKs > 24 in the AB magnitude system. Although depth and
area vary from field to field, the overall depth and large area of this dataset
make it one of the deepest wide-field NIR imaging surveys to date. This paper
discusses the observations, data reduction, and bright galaxy counts in these
fields. We compare the slope of the bright galaxy counts with the Two Micron
All Sky Survey (2MASS) and other counts from the literature and explore the
relationship between slope and supergalactic latitude. The slope near the
supergalactic equator is sub- Euclidean on average pointing to the possibility
of a decreasing average space density of galaxies by ~ 10-15% over scales of ~
250-350 Mpc. On the contrary, the slope at high supergalactic latitudes is
strongly super-Euclidean on average suggesting an increase in the space density
of galaxies as one moves from the voids just above and below the supergalactic
plane out to distances of ~ 250-350 Mpc. These results suggest that local large
scale structure could be responsible for large discrepancies in the measured
slope between different studies in the past. In addition, the local universe
away from the supergalactic plane appears to be underdense by ~ 25-100%
relative to the space densities of a few hundred megaparsecs distant. Subject
headings: cosmology: observations and large scale structure of
universe-galaxies: fundamental parameters (counts)-infrared: galaxiesComment: Accepted to ApJS, 18 Pages, 14 Figures, 8 Table
The OPTX Project I: The Flux and Redshift Catalogs for the CLANS, CLASXS, and CDF-N fields
We present the redshift catalogs for the X-ray sources detected in the
Chandra Deep Field North (CDF-N), the Chandra Large Area Synoptic X-ray Survey
(CLASXS), and the Chandra Lockman Area North Survey (CLANS). The catalogs for
the CDF-N and CLASXS fields include redshifts from previous work, while the
redshifts for the CLANS field are all new. For fluxes above 10^-14 ergs cm^-2
s^-1 (2-8 keV) we have redshifts for 76% of the sources. We extend the redshift
information for the full sample using photometric redshifts. The goal of the
OPTX Project is to use these three surveys, which are among the most
spectroscopically complete surveys to date, to analyze the effect of spectral
type on the shape and evolution of the X-ray luminosity functions and to
compare the optical spectral types with the X-ray spectral properties.
We also present the CLANS X-ray catalog. The nine ACIS-I fields cover a solid
angle of ~0.6 square degrees and reach fluxes of 7x10^-16 ergs cm^-2 s^-1
(0.5-2 keV) and 3.5x10^-15 ergs cm^-2 s^-1 (2-8 keV). We find a total of 761
X-ray point sources. Additionally, we present the optical and infrared
photometric catalog for the CLANS X-ray sources, as well as updated optical and
infrared photometric catalogs for the X-ray sources in the CLASXS and CDF-N
fields.
The CLANS and CLASXS surveys bridge the gap between the ultradeep pencil-beam
surveys, such as the CDFs, and the shallower, very large-area surveys. As a
result, they probe the X-ray sources that contribute the bulk of the 2-8 keV
X-ray background and cover the flux range of the observed break in the
logN-logS distribution. We construct differential number counts for each
individual field and for the full sample.Comment: Published in The Astrophysical Journal Supplement. 18 pages, 16
figures, 14 table
The OPTX Project IV: How Reliable is [OIII] as a Measure of AGN Activity?
We compare optical and hard X-ray identifications of AGNs using a uniformly
selected (above a flux limit of f_2-8 keV = 3.5e-15 erg/cm2/s) and highly
optically spectroscopically complete ( > 80% for f_2-8 keV > 1e-14 erg/cm2/s
and > 60% below) 2-8 keV sample observed in three Chandra fields (CLANS,
CLASXS, and the CDF-N). We find that empirical emission-line ratio diagnostic
diagrams misidentify 20-50% of the X-ray selected AGNs that can be put on these
diagrams as star formers, depending on which division is used. We confirm that
there is a large (2 orders in magnitude) dispersion in the log ratio of the
[OIII]5007A to hard X-ray luminosities for the non-broad line AGNs, even after
applying reddening corrections to the [OIII] luminosities. We find that the
dispersion is similar for the broad-line AGNs, where there is not expected to
be much X-ray absorption from an obscuring torus around the AGN nor much
obscuration from the galaxy along the line-of-sight if the AGN is aligned with
the galaxy. We postulate that the X-ray selected AGNs that are misidentified by
the diagnostic diagrams have low [OIII] luminosities due to the complexity of
the structure of the narrow-line region, which causes many ionizing photons
from the AGN not to be absorbed. This would mean that the [OIII] luminosity can
only be used to predict the X-ray luminosity to within a factor of ~3 (one
sigma). Despite selection effects, we show that the shapes and normalizations
of the [OIII] and transformed hard X-ray luminosity functions show reasonable
agreement, suggesting that the [OIII] samples are not finding substantially
more AGNs at low redshifts than hard X-ray samples.Comment: Accepted for publication in the Astrophysical Journal. 11 pages, 10
figure
Measuring the Sources of the Intergalactic Ionizing Flux
We use a wide-field (0.9 square degree) X-ray sample with optical and GALEX
ultraviolet observations to measure the contribution of Active Galactic Nuclei
(AGNs) to the ionizing flux as a function of redshift. Our analysis shows that
the AGN contribution to the metagalactic ionizing background peaks around z=2.
The measured values of the ionizing background from the AGNs are lower than
previous estimates and confirm that ionization from AGNs is insufficient to
maintain the observed ionization of the intergalactic medium (IGM) at z>3. We
show that only sources with broad lines in their optical spectra have
detectable ionizing flux and that the ionizing flux seen in an AGN is not
correlated with its X-ray color. We also use the GALEX observations of the
GOODS-N region to place a 2-sigma upper limit of 0.008 on the average
ionization fraction fnu(700 A)/fnu(1500 A) for 626 UV selected galaxies in the
redshift range z=0.9-1.4. We then use this limit to estimate an upper bound to
the galaxy contribution in the redshift range z=0-5. If the z~1.15 ionization
fraction is appropriate for higher redshift galaxies, then contributions from
the galaxy population are also too low to account for the IGM ionization at the
highest redshifts (z>4).Comment: 15 pages, Accepted by The Astrophysical Journa
Recommended from our members
Rights, responsibilities and reform: a study of French justice (1990-2016)
The principal questions addressed in this portfolio of eleven publications
concern the reforms to French justice at the end of the twentieth and beginning
of the twenty-first centuries. The portfolio is accompanied by a supporting
statement explaining the genesis and chronology of the portfolio, its originality and
the nature of the submission's distinct contribution to knowledge.
The thesis questions whether the reforms protect the rights of the defence
adequately. It considers how the French state views its responsibility to key
figures in criminal justice, be they suspected and convicted criminals, the
victims of offences or the professionals who are prosecuting the offences. It
reflects upon the role of the examining magistrate, the delicate relationship
between justice, politics and the media, breaches of confidentiality and the
catastrophic conditions in which suspects and prisoners are detained in French
prisons. It then extends its scope to a case study of the prosecution of violent
crimes before the International Criminal Tribunal for Rwanda, and discovers
significant flaws in procedures even at international levels. In concluding, it asks
whether, given the challenges facing the French criminal justice system, French
courts are adequately equipped to assure justice when suspects charged with
the most serious international crimes appear before them under the principle of
universal jurisdiction.
The research, carried out over a number of years, relies predominantly on an
analysis of French-language sources and represents a unique contribution to
the understanding and knowledge of French justice for an English-speaking
public at the turn of the twenty-first century
France, universal jurisdiction and Rwandan génocidaires: the Simbikangwa trial
YesIn 2014, twenty years after the Rwandan genocide, the first trial took place in France of a Rwandan génocidaire, Pascal Simbikangwa, despite the presence on French territory of a number of genocide suspects for many years, various extradition requests by Rwanda – declined by France – and numerous arrests and investigations. This article looks at issues of jurisdiction regarding the Simbikangwa case and the reasons the French courts heard his case, and examines some issues which may be of significance in the choice of arena for the bringing to justice of Rwandans genocide suspects living in France in future
How far has the International Criminal Tribunal for Rwanda really come since Akayesu in the prosecution and investigation of sexual offences committed against women? An analysis of Ndindiliyimana et al
YesDuring the first trial before the International Criminal Tribunal for Rwanda (ICTR), that of Jean-Paul Akayesu, it became evident that many Tutsi and moderate Hutu women had been raped, that “rape was the rule and its absence was the exception”.1 Although, initially, not a single charge of sexual violence was proffered against Akayesu, presiding judge Navanethem Pillay interrupted the proceedings, allowing ICTR prosecutors to amend the indictment and include counts of rape and sexual violence. Akayesu subsequently became the first case to recognise the concept of genocidal rape.
However, post-Akayesu, comparatively few defendants appearing before the ICTR have been convicted of sexual violence. An analysis of the recent case of Ndindiliyimana et al2 reveals that major shortcomings beset the investigation and prosecution procedures, so that crimes of sexual violence go unpunished, although research suggests that adequate legislation is in place at the ICTR to prosecute rape
and sexual violence successfully
The Resolved Near-Infrared Extragalactic Background
We present a current best estimate of the integrated near-infrared (NIR)
extragalactic background light (EBL) attributable to resolved galaxies in J, H,
and Ks. Our results in units of nW m-2 sr-1 are 11.7+5.6 -2.6 in J, 11.5+4.5
-1.5 in H and 10.0+2.8 -0.8 in Ks. We derive these new limits by combining our
deep wide-field NIR photometry from five widely separated fields with other
studies from the literature to create a galaxy counts sample that is highly
complete and has good counting statistics out to JHKs ~ 27-28. As part of this
effort we present new ultradeep Ks-band galaxy counts from 22 hours of
observations with the Multi Object Infrared Camera and Spectrograph (MOIRCS)
instrument on the Subaru Telescope. We use this MOIRCS Ks-band mosaic to
estimate the total missing flux from sources beyond our detection limits. Our
new limits to the NIR EBL are in basic agreement with, but 10 - 20% higher than
previous estimates, bringing them into better agreement with estimates of the
total NIR EBL (resolved + unresolved sources) obtained from TeV gamma-ray
opacity measurements and recent direct measurements of the total NIR EBL. We
examine field to field variations in our photometry to show that the integrated
light from galaxies is isotropic to within uncertainties, consistent with the
expected large-scale isotropy of the EBL. Our data also allow for a robust
estimate of the NIR light from Galactic stars, which we find to be 14.7 +/- 2.4
in J, 10.1 +/- 1.9 in H and 7.6 +/- 1.8 in Ks in units of nW m-2 sr-1.Comment: Accepted to Ap
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