3,251 research outputs found
The REX survey: a search for Radio Emitting X-ray sources
We present the scientific goals, the strategy and the first results of the
REX project, an effort aimed at creating a sizable and statistically complete
sample of Radio Emitting X-ray sources (REX) using the available data from a
VLA survey and the ROSAT PSPC archive. Through a positional cross-correlation
of the two data sets we have derived a sample of about 1600 REX. Among the 393
REX identified so far a high fraction is represented by AGNs, typically radio
loud QSOs and BL Lacs. The remaining sources are galaxies, typically radio
galaxies isolated or in cluster. Thanks to the low flux limits in the radio and
in the X-ray band and the large area of sky covered by the survey, we intend to
derive a new complete and unbiased sample of BL Lacs which will contain both
``RBL'' and ``XBL'' type objects. In this way, the apparent dichotomy resulting
from the current samples of BL Lacs will be directly analyzed in a unique
sample. Moreover, the high number of BL Lacs expected in the REX sample (about
200) will allow an accurate estimate of their statistical properties. To date,
we have discovered 15 new BL Lacs and 11 BL Lac candidates with optical
properties intermediate between those of a typical elliptical galaxy and those
of a typical BL Lac object. These objects could harbour weak sources of
non-thermal continuum in their nuclei and, if confirmed, they could represent
the faint tail of the BL Lac population. The existence of such ``weak'' BL Lacs
is matter of discussion in recent literature and could lead to a re-assessment
of the defining criteria of a BL Lac and, consequently, to a revision of their
cosmological and statistical properties.Comment: 30 pages, 13 figures, accepted for publication to Ap
Emission Line AGNs from the REX survey: Results from optical spectroscopy
We present 71 Emission Line objects selected from the REX survey. Except for
3 of them, for which the presence of an active nucleus is dubious, all these
sources are Active Galactic Nuclei (QSOs, Seyfert galaxies, emission line
radiogalaxies). In addition, we present the spectra of other 19 AGNs included
in a preliminary version of the REX catalog but not in the final one. The
majority (80) of the 90 sources presented in this paper is newly discovered.
Finally, we present the general properties in the radio and in the X-ray band
of all the AGNs discovered so far in the REX survey.Comment: 27 pages. To be published in Astronomy and Astrophysics, Supplement
Series. Better quality figures can be asked to the autho
An X-ray review of MS1054-0321: hot or not?
XMM-Newton observations are presented for the z=0.83 cluster of galaxies
MS1054-0321, the highest redshift cluster in the Einstein Extended Medium
Sensitivity Survey (EMSS). The temperature inferred by the XMM-Newton data,
T=7.2 (+0.7, -0.6) keV, is much lower than the temperature previously reported
from ASCA data, T=12.3 (+3.1, -2.2) keV (Donahue et al. 1998), and a little
lower than the Chandra temperature, T=10.4(+1.7, -1.5) keV, determined by
Jeltema et al. 2001. The discrepancy between the newly derived temperature and
the previously derived temperatures is discussed in detail. If one allows the
column density to be a free parameter, then the best fit temperature becomes
T=8.6 (+1.2, -1.1) keV, and the best fit column density becomes N_(H)=1.33
(+0.15 -0.14) x 10^20 atoms/cm^2. The iron line is well detected in the
XMM-Newton spectrum with a value for the abundance of Z=0.33 (+0.19 -0.18)
Zsol, in very good agreement with previous determinations. The derived XMM
X-ray luminosity for the overall cluster in the 2-10 keV energy band is
L_X=(3.81 +/- 0.19) x 10^44 h^-2 erg s^-1 while the bolometric luminosity is
L_BOL=(8.05+/-0.40) x 10^44 h^-2 erg s^-1. The XMM-Newton data confirm the
substructure in the cluster X-ray morphology already seen by ROSAT and in much
more detail by Chandra. The central weak lensing clump is coincident with the
main cluster component and has a temperature T=8.1 (+1.3, -1.2) keV. The
western weak lensing clump coincides with the western X-ray component which is
much cooler with a temperature T=5.6 (+0.8, -0.6)$ keV. Given the newly
determined temperature, MS1054-0321 is no longer amongst the hottest clusters
known.Comment: To appear in the A&A main Journal, 13 pages including 3 postscript
figures and 4 tables. Figs. 1, 4, 5 and 7 are too large and are not given
here. The whole paper as pdf file is posted at
http://www.ira.cnr.it/~gioia/PUB/publications.htm
Angiotensin type-2 (AT-2)-receptor activation reduces renal fibrosis in cyclosporine nephropathy: evidence for blood-pressure independent effect
Compound 21 (C21), selective agonist of AT2 receptors, shows antinflammatory effects in hypertension and nephroprotection in diabetes. The aim of this study was to evaluate the effects of C21 in cyclosporine nephropathy, which is characterized mainly by tubulo-interstitial fibrosis. Ten days before and during the experimental periods, low-salt diet was administered to Sprague Dawley rats. Cyclosporine-A (15mg/kg/day, i.p.) and cyclosporine-A plus C21 (0.3 mg/kg /day, i.p) were administered for 1 and 4 weeks. Control groups was left without any treatment. Blood pressure (plethysmographic method) and 24 hour albuminuria were measured once a week. At the end of the experiments, the kidneys were excised for histomorphometric analysis of renal fibrosis and for immunohistochemical evaluation of inflammatory infiltrates and type I and IV collagen expression.After 1 and 4 weeks, the rats treated with cyclosporine showed a significant increase (p <0.01) in blood pressure, no significant changes in albuminuria, a significant increase (p <0.01) in glomerular and tubulo-interstitial fibrosis and inflammatory infiltrates as compared to the control rats. Treatment with C21 did not modify the cyclosporine dependent increase of blood pressure, which was higher than in control rats, but after 4 weeks of treatment significantly reduced (p <0.01) glomerular and tubulo-interstitial fibrosis, type 1 collagen expression and macrophage infiltration, as compared to rats treated with cyclosporine.The administration of C21 showed a protective effect on cyclosporine nephropathy, decreasing renal fibrosis and macrophage infiltration. These data suggest that C21 may counteract tubulo-interstitial fibrosis, the most potent predictor of the progression of renal diseases
High redshift X-ray galaxy clusters. I. The impact of point sources on the cluster properties
The current generation of X-ray observatories like Chandra allows studies
with very fine spatial details. It is now possible to resolve X-ray point
sources projected into the cluster diffuse emission and exclude them from the
analysis to estimate the ``correct'' X-ray observables. In order to verify the
incidence of point sources on the cluster thermal emission and to evaluate the
impact of their non-thermal emission on the determination of cluster
properties, we used a sample of 18 high-z (0.25 < z < 1.01) clusters from the
Chandra archive. We performed a detailed analysis of the cluster properties and
compared the changes observed in the X-ray observables, like temperature and
luminosity or their inter-relation, when one keeps the point sources in the
analysis. The point sources projected into the cluster extended emission affect
the estimates of cluster temperature or luminosity considerably (up to 13% and
17% respectively). These percentages become even larger for clusters with z >
0.7 where temperature and luminosity increase up to 24% and 22%, respectively.
Thus the point sources should be removed to correctly estimate the cluster
properties. However the inclusion of the point sources does not impact
significantly the slope and normalization of the L-T relationship since for
each cluster the correction to be applied to T and L produces a moderate shift
in the L-T plane almost parallel to the best-fit of the ``correct'' L-T
relation.Comment: 16 pages, 18 postscript figures. Accepted for publication in
Astronomy & Astrophysic
Clinical significance of epithelial-to-mesenchymal transition in laryngeal carcinoma: Its role in the different subsites
Background: During epithelial-to-mesenchymal transition, cancer cells lose adhesion capacity gaining migratory properties. The role of the process on prognosis has been evaluated in 50 cases of laryngeal carcinoma. Methods: E-cadherin, N-cadherin, β-catenin, α-catenin, γ-catenin, caveolin-1, and vimentin immunohistochemical expression were evaluated using a double score based on staining intensity and cellular localization. Results: Cytoplasmic E-cadherin and α/γ catenin staining were associated with a decrease in survival, cytoplasmic β-catenin was associated with advanced stage, and N-cadherin and vimentin expression were associated with poor differentiation and tumor relapse. On the basis of cancer cells, epithelial or mesenchymal morphological and immunophenotypic similarity we identified 4 main subgroups correlated with a transition to a more undifferentiated phenotype, which have a different pattern of relapse and survival. Conclusion: The negative prognostic role of epithelial-to-mesenchymal transition has been confirmed and a predictive role in glottic tumors has been suggested, leading us to propose epithelial-to-mesenchymal transition as an additional adverse feature in laryngeal carcinoma
The 3D soft X-ray cluster-AGN cross-correlation function in the ROSAT NEP survey
X-ray surveys facilitate investigations of the environment of AGNs. Deep
Chandra observations revealed that the AGNs source surface density rises near
clusters of galaxies. The natural extension of these works is the measurement
of spatial clustering of AGNs around clusters and the investigation of relative
biasing between active galactic nuclei and galaxies near clusters.The major
aims of this work are to obtain a measurement of the correlation length of AGNs
around clusters and a measure of the averaged clustering properties of a
complete sample of AGNs in dense environments. We present the first measurement
of the soft X-ray cluster-AGN cross-correlation function in redshift space
using the data of the ROSAT-NEP survey. The survey covers 9x9 deg^2 around the
North Ecliptic Pole where 442 X-ray sources were detected and almost completely
spectroscopically identified. We detected a >3sigma significant clustering
signal on scales s<50 h70^-1 Mpc. We performed a classical maximum-likelihood
power-law fit to the data and obtained a correlation length s_0=8.7+1.2-0.3
h_70-1 Mpc and a slope gamma=1.7$^+0.2_-0.7 (1sigma errors). This is a strong
evidence that AGNs are good tracers of the large scale structure of the
Universe. Our data were compared to the results obtained by cross-correlating
X-ray clusters and galaxies. We observe, with a large uncertainty, that the
bias factor of AGN is similar to that of galaxies.Comment: 4 pages, 2 figure, proceedings of the Conference "At the edge of the
Universe", Sintra Portugal, October 2006. To be published on the Astronomical
Society of the Pacific Conference Series (ASPCS
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