1,545 research outputs found
Selecting background galaxies in weak-lensing analysis of galaxy clusters
In this paper, we present a new method to select the faint, background
galaxies used to derive the mass of galaxy clusters by weak lensing.
The method is based on the simultaneous analysis of the shear signal, that
should be consistent with zero for the foreground, unlensed galaxies, and of
the colors of the galaxies: photometric data from the COSMic evOlution Survey
are used to train the color selection. In order to validate this methodology,
we test it against a set of state-of-the-art image simulations of mock galaxy
clusters in different redshift [] and mass
[] ranges, mimicking medium-deep multicolor
imaging observations (e.g. SUBARU, LBT).
The performance of our method in terms of contamination by unlensed sources
is comparable to a selection based on photometric redshifts, which however
requires a good spectral coverage and is thus much more observationally
demanding. The application of our method to simulations gives an average ratio
between estimated and true masses of . As a further test,
we finally apply our method to real data, and compare our results with other
weak lensing mass estimates in the literature: for this purpose we choose the
cluster Abell 2219 (), for which multi-band (BVRi) data are publicly
available.Comment: MNRAS, Accepted 2016 February 2
A weak lensing analysis of the PLCK G100.2-30.4 cluster
We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4,
derived from a weak lensing analysis of deep SUBARU griz images. We perform a
careful selection of the background galaxies using the multi-band imaging data,
and undertake the weak lensing analysis on the deep (1hr) r-band image. The
shape measurement is based on the KSB algorithm; we adopt the PSFex software to
model the Point Spread Function (PSF) across the field and correct for this in
the shape measurement. The weak lensing analysis is validated through extensive
image simulations. We compare the resulting weak lensing mass profile and total
mass estimate to those obtained from our re-analysis of XMM-Newton
observations, derived under the hypothesis of hydrostatic equilibrium. The
total integrated mass profiles are in remarkably good agreement, agreeing
within 1 across their common radial range. A mass is derived for the cluster from our weak lensing
analysis. Comparing this value to that obtained from our reanalysis of
XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 0.1. This is
compatible within 1 with the value of (1-b) obtained by Planck
Collaboration XXIV from their calibration of the bias factor using
newly-available weak lensing reconstructed masses.Comment: 11 pages, 12 figures, accepted for publication on Astronomy &
Astrophysics; updates in affiliation
1WGAJ1226.9+3332: a high redshift cluster discovered by Chandra
We report the detection of 1WGAJ1226.9+3332 as an arcminute scale extended
X-ray source with the Chandra X-ray Observatory. The Chandra observation and R
and K band imaging strongly support the identification of 1WGAJ1226.9+3332 as a
high redshift cluster of galaxies, most probably at z=0.85 +- 0.15, with an
inferred temperature kT =10 (+4;-3) keV and an unabsorbed luminosity (in a
r=120" aperture) of 1.3 (+0.16;-0.14) x 1e45 erg/s (0.5-10 keV). This
indication of redshift is also supported by the K and R band imaging, and is in
agreement with the spectroscopic redshift of 0.89 found by Ebeling et al.
(2001). The surface brightness profile is consistent with a beta-model with
beta=0.770 +- 0.025, rc=(18.1 +-0.9)" (corresponding to 101 +- 5 kpc at
z=0.89), and S(0)=1.02 +- 0.08 counts/arcsec**2. 1WGAJ1226.9+3332 was selected
as an extreme X-ray loud source with FX/FV>60; this selection method, thanks to
the large area sampled, seems to be a highly efficient method for finding
luminous high z clusters of galaxies.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in ApJ main
journal. Uses emulateapj.st
An X-ray and optical study of the cluster A33
We report the first detailed X-ray and optical observations of the
medium-distant cluster A33 obtained with the Beppo-SAX satellite and with the
UH 2.2m and Keck II telescopes at Mauna Kea. The information deduced from X-ray
and optical imaging and spectroscopic data allowed us to identify the X-ray
source 1SAXJ0027.2-1930 as the X-ray counterpart of the A33 cluster. The faint,
F_{2-10 keV} \approx 2.4 \times 10^{-13} \ergscm2, X-ray source
1SAXJ0027.2-1930, arcmin away from the optical position of the cluster
as given in the Abell catalogue, is identified with the central region of A33.
Based on six cluster galaxy redshifts, we determine the redshift of A33,
; this is lower than the value derived by Leir and Van Den Bergh
(1977). The source X-ray luminosity, L_{2-10 keV} = 7.7 \times 10^{43} \ergs,
and intracluster gas temperature, keV, make this cluster interesting
for cosmological studies of the cluster relation at intermediate
redshifts. Two other X-ray sources in the A33 field are identified. An AGN at
z0.2274, and an M-type star, whose emission are blended to form an extended
X-ray emission arcmin north of the A33 cluster. A third possibly
point-like X-ray source detected arcmin north-west of A33 lies close
to a spiral galaxy at z0.2863 and to an elliptical galaxy at the same
redshift as the cluster.Comment: 9 pages, 6 Figures, Latex (using psfig,l-aa), to appear in Astronomy
and Astrophysics S. (To get better quality copies of Figs.1-3 send an email
to: [email protected]). A&AS, in pres
Medullary sponge kidney: unusual finding in kidney transplant recipient
Background: Medullary sponge kidney is generally considered a benign condition, gold standard for the diagnosis is urography but it has almost been replaced by UroCT that did not present the same sensibility. Although it is really rare, our sonography's findings were consistent with medullary sponge kidney in the transplanted kidneys.Case presentation: A 45-year-old woman with a long history of double-kidney transplantation complained of frequent urinary tract infections, a history of vague loin pain and came to our attention for sonography follow-up. Her kidney function was normal, we did not find signs of infections in the transplanted kidneys and urinary findings were normal. Curiously, the transplanted kidneys came from a newborn and the patient received a double-kidney transplantation in order to guarantee a satisfactory renal function.Conclusions: Despite a long history of kidney transplantation, genetic disease should not be forgotten when symptoms and images recall to specific inherited alterations. Sonography has to be considered in diagnostic path of kidney cystic disease
Testing hydrostatic equilibrium in galaxy cluster MS 2137
We test the assumption of strict hydrostatic equilibrium in galaxy cluster
MS2137.3-2353 (MS 2137) using the latest CHANDRA X-ray observations and results
from a combined strong and weak lensing analysis based on optical observations.
We deproject the two-dimensional X-ray surface brightness and mass surface
density maps assuming spherical and spheroidal dark matter distributions. We
find a significant, 40%-50%, contribution from non-thermal pressure in the core
assuming a spherical model. This non-thermal pressure support is similar to
what was found by Molnar et al. (2010) using a sample of massive relaxed
clusters drawn from high resolution cosmological simulations. We have studied
hydrostatic equilibrium in MS 2137 under the assumption of elliptical cluster
geometry adopting prolate models for the dark matter density distribution with
different axis ratios. Our results suggest that the main effect of ellipticity
(compared to spherical models) is to decrease the non-thermal pressure support
required for equilibrium at all radii without changing the distribution
qualitatively. We find that a prolate model with an axis ratio of 1.25 (axis in
the line of sight over perpendicular to it) provides a physically acceptable
model implying that MS 2137 is close to hydrostatic equilibrium at about
0.04-0.15 Rvir and have an about 25% contribution from non-thermal pressure at
the center. Our results provide further evidence that there is a significant
contribution from non-thermal pressure in the core region of even relaxed
clusters, i.e., the assumption of hydrostatic equilibrium is not valid in this
region, independently of the assumed shape of the cluster.Comment: 11 pages, 4 figures, accepted for publication in Ap
The Feedback-Regulated Growth of Black Holes and Bulges through Gas Accretion and Starbursts in Cluster Central Dominant Galaxies
We present an analysis of the growth of black holes through accretion and
bulges through star formation in 33 galaxies at the centers of cooling flows.
Most of these systems show evidence of cavities in the intracluster medium
(ICM) inflated by radio jets emanating from their active galactic nuclei (AGN).
We present a new and extensive analysis of X-ray cavities in these systems. We
find that AGN are energetically able to balance radiative losses (cooling) from
the ICM in more than half of our sample. Using a subsample of 17 systems, we
examine the relationship between cooling and star formation. We find that the
star formation rates are approaching or are comparable to X-ray and far UV
limits on the rates of gas condensation onto the central galaxy. The remaining
radiative losses could be offset by AGN feedback. The vast gulf between
radiative losses and the sink of cooling material, which has been the primary
objection to cooling flows, has narrowed and, in some cases, is no longer a
serious issue. Using the cavity (jet) powers, we place strong lower limits on
the rate of growth of supermassive black holes in central galaxies, and we find
that they are growing at an average rate of ~ 0.1 solar masses per year, with
some systems growing as quickly as ~ 1 solar mass per year. We find a trend
between bulge growth (star formation) and black hole growth that is
approximately in accordance with the slope of the local (Magorrian) relation
between black hole and bulge mass. However, the large scatter in the trend
suggests that bulges and black holes do not always grow in lock step.
(Abridged)Comment: 17 pages, 6 figures, accepted to ApJ. Minor changes to text and
figure
Body mass index in HER2-negative metastatic breast cancer treated with first-line paclitaxel and bevacizumab
The evidence emerged from the TOURANDOT trial encourages evaluating the role of anthropometric determinants on treatment outcomes in HER2-negative metastatic breast cancer patients treated with bevacizumab-including regimens. We thus analyzed data from a subgroup of these patients from a larger cohort previously assessed for treatment outcomes. Patients were included in the present analysis if body mass index values had been recorded at baseline. Clinical benefit rates, progression free survival and overall survival were assessed for the overall study population and subgroups defined upon molecular subtype. One hundred ninety six patients were included (N:196). Body mass index showed no impact on clinical benefit rates in the overall study sample and in the luminal cancer subset (p = 0.12 and p = 0.79, respectively), but did so in the triple negative subgroup, with higher rates in patients with body mass index â„25 (p = 0.03). In the overall study sample, body mass index did no impact progression free or overall survival (p = 0.33 and p = 0.67, respectively). Conversely, in triple negative patients, progression free survival was significantly longer with body mass index â„25 (6 vs 14 months, p = 0.04). In this subset, overall survival was more favorable (25 vs 19 months, p = 0.02). The impact of the molecular subtype was confirmed in multivariate models including the length of progression free survival, and number of metastatic sites (p < 0.0001). Further studies are warranted to confirm our findings in more adequately sized, ad hoc, prospective studies
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