5,217 research outputs found
High-Energy Cosmology: gamma rays and neutrinos from beyond the galaxy
Our knowledge of the high-energy universe is undergoing a period of rapid
change as new astronomical detectors of high-energy radiation start to operate
at their design sensitivities. Now is a boomtime for high-energy astrophysics,
with new discoveries from Swift and HESS, results from MAGIC and VERITAS
starting to be reported, the upcoming launches of the gamma-ray space
telescopes GLAST and AGILE, and anticipated data releases from IceCube and
Auger. A formalism for calculating statistical properties of cosmological
gamma-ray sources is presented. Application is made to model calculations of
the statistical distributions of gamma-ray and neutrino emission from (i)
beamed sources, specifically, long-duration GRBs, blazars, and extagalactic
microquasars, and (ii) unbeamed sources, including normal galaxies, starburst
galaxies and clusters. Expressions for the integrated intensities of faint
beamed and unbeamed high-energy radiation sources are also derived. A toy model
for the background intensity of radiation from dark-matter annihilation taking
place in the early universe is constructed. Estimates for the gamma-ray fluxes
of local group galaxies, starburst, and infrared luminous galaxies are briefly
reviewed. Because the brightest extragalactic gamma-ray sources are flaring
sources, and these are the best targets for sources of PeV -- EeV neutrinos and
ultra-high energy cosmic rays, rapidly slewing all-sky telescopes like MAGIC
and an all-sky gamma-ray observatory beyond Milagro will be crucial for optimal
science return in the multi-messenger age.Comment: 10 pages, 3 figs, accepted for publication in the Barcelona
Conference on Multimessenger Astronomy; corrected eq. 27, revised Fig. 3,
added 2 ref
The Farthest Known Supernova: Support for an Accelerating Universe and a Glimpse of the Epoch of Deceleration
We present photometric observations of an apparent Type Ia supernova (SN Ia)
at a redshift of ~1.7, the farthest SN observed to date. SN 1997ff, was
discovered in a repeat observation by the HST of the HDF-), and serendipitously
monitored with NICMOS on HST throughout the GTO campaign. The SN type can be
determined from the host galaxy type:an evolved, red elliptical lacking enough
recent star formation to provide a significant population of core-collapse SNe.
The class- ification is further supported by diagnostics available from the
observed colors and temporal behavior of the SN, both of which match a typical
SN Ia. The photo- metric record of the SN includes a dozen flux measurements in
the I, J, and H bands spanning 35 days in the observed frame. The redshift
derived from the SN photometry, z=1.7+/-0.1, is in excellent agreement with the
redshift estimate of z=1.65+/-0.15 derived from the
U_300,B_450,V_606,I_814,J_110,J_125,H_160, H_165,K_s photometry of the galaxy.
Optical and near-infrared spectra of the host provide a very tentative
spectroscopic redshift of 1.755. Fits to observations of the SN provide
constraints for the redshift-distance relation of SNe~Ia and a powerful test of
the current accelerating Universe hypothesis. The apparent SN brightness is
consistent with that expected in the decelerating phase of the preferred
cosmological model, Omega_M~1/3, Omega_Lambda~2/3. It is inconsistent with grey
dust or simple luminosity evolution, candidate astro- physical effects which
could mimic past evidence for an accelerating Universe from SNe Ia at z~0.5.We
consider several sources of possible systematic error including lensing, SN
misclassification, selection bias, and calibration errors. Currently, none of
these effects appears likely to challenge our conclusions.Comment: Accepted to the Astrophysical Journal 38 pages, 15 figures, Pretty
version available at http://icarus.stsci.edu/~stefano/ariess.tar.g
The VLA-COSMOS Survey. IV. Deep Data and Joint Catalog
In the context of the VLA-COSMOS Deep project additional VLA A array
observations at 1.4 GHz were obtained for the central degree of the COSMOS
field and combined with the existing data from the VLA-COSMOS Large project. A
newly constructed Deep mosaic with a resolution of 2.5" was used to search for
sources down to 4 sigma with 1 sigma ~ 12 microJy/beam in the central 50'x50'.
This new catalog is combined with the catalog from the Large project (obtained
at 1.5"x1.4" resolution) to construct a new Joint catalog. All sources listed
in the new Joint catalog have peak flux densities of >5 sigma at 1.5" and/or
2.5" resolution to account for the fact that a significant fraction of sources
at these low flux levels are expected to be slighty resolved at 1.5"
resolution. All properties listed in the Joint catalog such as peak flux
density, integrated flux density and source size are determined in the 2.5"
resolution Deep image. In addition, the Joint catalog contains 43 newly
identified multi-component sources.Comment: 34 pages, 20 figures (3 at reduced resolution). Accepted for
publication in ApJS
Radio galaxy feedback in X-ray selected groups from COSMOS: the effect on the ICM
We quantify the importance of the mechanical energy released by
radio-galaxies inside galaxy groups. We use scaling relations to estimate the
mechanical energy released by 16 radio-AGN located inside X-ray detected galaxy
groups in the COSMOS field. By comparing this energy output to the host groups'
gravitational binding energy, we find that radio galaxies produce sufficient
energy to unbind a significant fraction of the intra-group medium. This
unbinding effect is negligible in massive galaxy clusters with deeper potential
wells. Our results correctly reproduce the breaking of self-similarity observed
in the scaling relation between entropy and temperature for galaxy groups.Comment: Accepted for publication in the Astrophysical Journal. 12 Page
Photometric Redshifts of Galaxies in COSMOS
We measure photometric redshifts and spectral types for galaxies in the
COSMOS survey. We use template fitting technique combined with luminosity
function priors and with the option to simultaneously estimate dust extinction
(i.e. E(B-V)) for each galaxy.Our estimated redshifts are accurate to i<25 and
z~1.2.
Using simulations with sampling and noise characteristics similar to those in
COSMOS, the accuracy and reliability is estimated for the photometric redshifts
as a function of the magnitude limits of the sample, S/N ratios and the number
of bands used. From the simulations we find that the ratio of derived 95%
confidence interval in the redshift probability distribution to the estimated
photometric redshift (D95) can be used to identify and exclude the catastrophic
failures in the photometric redshift estimates.
We compare the derived redshifts with high-reliability spectroscopic
redshifts for a sample of 868 normal galaxies with z < 1.2 from zCOSMOS.
Considering different scenarios, depending on using prior, no prior and/or
extinction, we compare the photometric and spectroscopic redshifts for this
sample. This corresponds to an rms scatter of 0.031, with a small number of
outliers (<2.5%). We also find good agreement (rms=0.10) between photometric
and spectroscopic redshifts for Type II AGNs.
We compare results from our photometric redshift procedure with three other
independent codes and find them in excellent agreement. We show preliminary
results, based on photometric redshifts for the entire COSMOS sample (to i < 25
mag.).Comment: 38 pages; 14 Figures; 7 Tables. Accepted for Publication in ApJS.
COSMOS Special Issu
A Multiwavelength Study of a Sample of 70 micron Selected Galaxies in the COSMOS Field I: Spectral Energy Distributions and Luminosities
We present a large robust sample of 1503 reliable and unconfused 70microm
selected sources from the multiwavelength data set of the Cosmic Evolution
Survey (COSMOS). Using the Spitzer IRAC and MIPS photometry, we estimate the
total infrared luminosity, L_IR (8--1000 microns), by finding the best fit
template from several different template libraries. The long wavelength 70 and
160 micron data allow us to obtain a reliable estimate of L_IR, accurate to
within 0.2 and 0.05 dex, respectively. The 70 micron data point enables a
significant improvement over the luminosity estimates possible with only a 24
micron detection. The full sample spans a wide range in L_IR, L_IR ~ 10^8-10^14
L_sun, with a median luminosity of 10^11.4 L_sun. We identify a total of 687
luminous, 303 ultraluminous, and 31 hyperluminous infrared galaxies (LIRGs,
ULIRGs, and HyLIRGs) over the redshift range 0.01<z<3.5 with a median redshift
of 0.5. Presented here are the full spectral energy distributions for each of
the sources compiled from the extensive multiwavelength data set from the
ultraviolet (UV) to the far-infrared (FIR). Using SED fits we find possible
evidence for a subset of cooler ultraluminous objects than observed locally.
However, until direct observations at longer wavelengths are obtained, the peak
of emission and the dust temperature cannot be well constrained. We use these
SEDs, along with the deep radio and X-ray coverage of the field, to identify a
large sample of candidate active galactic nuclei (AGN). We find that the
fraction of AGN increases strongly with L_IR, as it does in the local universe,
and that nearly 70% of ULIRGs and all HyLIRGs likely host a powerful AGN.Comment: 31 pages including 31 figures and 6 tables. Accepted for publication
in ApJ. The full resolution version is available here:
http://www.ifa.hawaii.edu/~jeyhan/paperI/Kartaltepe_70mic_PaperI.pd
Implementation of self management support for long term conditions in routine primary care settings: cluster randomised controlled trial
ObjectiveTo determine the effectiveness of an intervention to enhance self management support for patients with chronic conditions in UK primary care. Design Pragmatic, two arm, cluster randomised controlled trial.SettingGeneral practices, serving a population in northwest England with high levels of deprivation.Participants5599 patients with a diagnosis of diabetes (n=2546), chronic obstructive pulmonary disease (n=1634), and irritable bowel syndrome(n=1419) from 43 practices (19 intervention and 22 control practices).Intervention Practice level training in a whole systems approach to self management support. Practices were trained to use a range of resources: a tool to assess the support needs of patients, guidebooks on self management, and a web based directory of local self management resources. Training facilitators were employed by the health management organisation.Main Outcome MeasuresPrimary outcomes were shared decision making, self efficacy, and generic health related quality of life measured at 12 months. Secondary outcomes were general health, social or role limitations, energy and vitality, psychological wellbeing, self care activity,and enablement.ResultsWe randomised 44 practices and recruited 5599 patients, representing 43% of the eligible population on the practice lists. 4533 patients (81.0%) completed the six month follow-up and 4076 (72.8%)the 12 month follow-up.No statistically significant differences were found between patients attending trained practices and those attending control practices on any of the primary or secondary outcomes. All effect size estimates were well below the prespecified threshold of clinically important difference
Large Structures and Galaxy Evolution in COSMOS at z < 1.1
We present the first identification of large-scale structures (LSS) at z in the Cosmic Evolution Survey (COSMOS). The structures are identified
from adaptive smoothing of galaxy counts in the pseudo-3d space
(,z) using the COSMOS photometric redshift catalog. The
technique is tested on a simulation including galaxies distributed in model
clusters and a field galaxy population -- recovering structures on all scales
from 1 to 20\arcmin without {\it a priori} assumptions for the structure size
or density profile. Our procedure makes {\bf no} {\it a priori} selection on
galaxy spectral energy distribution (SED, for example the Red Sequence),
enabling an unbiased investigation of environmental effects on galaxy
evolution. The COSMOS photometric redshift catalog yields a sample of
galaxies with redshift accuracy, at z down to I mag. Using this sample of galaxies,
we identify 42 large-scale structures and clusters. abstract truncated for
astroph 25 line limit -- see preprintComment: 72 pages with 29 pages of figures, for cosmos apj suppl special issu
Juvenile idiopathic scoliosis treated with posterior arthrodesis and segmental pedicle screw instrumentation before the age of 9 years: a 5-year follow-up
<p>Abstract</p> <p>Study design</p> <p>Retrospective study.</p> <p>Objective</p> <p>To evaluate the radiological results of fusion with segmental pedicle screw fixation in juvenile idiopathic scoliosis with a minimum 5-year follow-up.</p> <p>Summary of background data</p> <p>Progression of spinal deformity after posterior instrumentation and fusion in immature patients has been reported by several authors. Segmental pedicle screw fixation has been shown to be effective in controlling both coronal and sagittal plane deformities. However, there is no long term study of fusion with segmental pedicle screw fixation in these group of patients.</p> <p>Methods</p> <p>Seven patients with juvenile idiopathic scoliosis treated by segmental pedicle screw fixation and fusion were analyzed. The average age of the patients was 7.4 years (range 5â9 years) at the time of the operation. All the patients were followed up 5 years or more (range 5â8 years) and were all Risser V at the most recent follow up. Three dimensional reconstruction of the radiographs was obtained and 3DStudio Max software was used for combining, evaluating and modifying the technical data derived from both 2d and 3d scan data.</p> <p>Results</p> <p>The preoperative thoracic curve of 56 ± 15° was corrected to 24 ± 17° (57% correction) at the latest follow-up. The lumbar curve of 43 ± 14° was corrected to 23 ± 6° (46% correction) at the latest follow-up. The preoperative thoracic kyphosis of 37 ± 13° and the lumbar lordosis of 33 ± 13° were changed to 27 ± 13° and 42 ± 21°, respectively at the latest follow-up. None of the patients showed coronal decompensation at the latest follow-up. Four patients had no evidence of crankshaft phenomenon. In two patients slight increase in Cobb angle at the instrumented segments with a significant increase in AVR suggesting crankshaft phenomenon was seen. One patient had a curve increase in both instrumented and non instrumented segments due to incorrect strategy.</p> <p>Conclusion</p> <p>In juvenile idiopathic curves of Risser 0 patients with open triradiate cartilages, routine combined anterior fusion to prevent crankshaft may not be warranted by posterior segmental pedicle screw instrumentation.</p
The zCOSMOS survey: the role of the environment in the evolution of the luminosity function of different galaxy types
Aims. An unbiased and detailed characterization of the galaxy luminosity function (LF) is a basic requirement in many astrophysical issues: it is of particular interest in assessing the role of the environment in the evolution of the LF of different galaxy types.
Methods. We studied the evolution in the B band LF to redshift z ~ 1 in the zCOSMOS 10k sample, for which both accurate galaxy classifications (spectrophotometric and morphological) and a detailed description of the local density field are available.
Results. The global B band LF exhibits a brightening of ~0.7 mag in M^* from z ~ 0.2 to z ~ 0.9. At low redshifts (z -20), while the bright end is populated mainly by spectrophotometric early types. At higher redshift, spectrophotometric late-type galaxies evolve significantly and, at redshift z ~ 1, the contribution from the various types to the bright end of the LF is comparable. The evolution for spectrophotometric early-type galaxies is in both luminosity and normalization: M* brightens by ~0.6 mag but Ï^â decreases by a factor ~1.7 between the first and the last redshift bin. A similar behaviour is exhibited by spectrophotometric late-type galaxies, but with an opposite trend for the normalization: a brightening of ~0.5 mag is present in M^*, while Ï^â increases by a factor ~1.8.â©Studying the role of the environment, we find that the global LF of galaxies in overdense regions has always a brighter M^* and a flatter slope. In low density environments, the main contribution to the LF is from blue galaxies, while for high density environments there is an important contribution from red galaxies to the bright end.â©The differences between the global LF in the two environments are not due to only a difference in the relative numbers of red and blue galaxies, but also to their relative luminosity distributions: the value of M^* for both types in underdense regions is always fainter than in overdense environments. These results indicate that galaxies of the same type in different environments have different properties.â©We also detect a differential evolution in blue galaxies in different environments: the evolution in their LF is similar in underdense and overdense regions between z ~ 0.25 and z ~ 0.55, and is mainly in luminosity. In contrast, between z ~ 0.55 and z ~ 0.85 there is little luminosity evolution but there is significant evolution in Ï^â, that is, however, different between the two environments: in overdense regions Ï^â increases by a factor ~1.6, while in underdense regions this increase reaches a factor ~2.8. Analyzing the blue galaxy population in more detail, we find that this evolution is driven mainly by the bluest types.
Conclusions. The âspecularâ evolution of late- and early-type galaxies is consistent with a scenario where a part of blue galaxies is transformed in red galaxies with increasing cosmic time, without significant changes in the fraction of intermediate-type galaxies. The bulk of this tranformation in overdense regions probably happened before z ~ 1, while it is still ongoing at lower redshifts in underdense environments
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