237 research outputs found
The rich cluster of galaxies ABCG 85.I. X-ray analysis
We present an X-ray analysis of the rich cluster ABCG 85 based on ROSAT PSPC
data. By applying an improved wavelet analysis, we show that our view of this
cluster is notably changed from what was previously believed (a main region and
a south blob). The main emission comes from the central part of the main body
of the cluster on which is superimposed that of a foreground group of galaxies.
The foreground group and the main cluster are separated (if redshifts are
cosmological) by 46 1/h_50 Mpc. The southern blob is clearly not a group: it is
resolved into X-ray emitting galaxies (in particular the second more luminous
galaxy of the main cluster). Several X-ray features are identified with bright
galaxies. We performed a spectral analysis and derived the temperature (T),
metallicity (Z) and hydrogen column density NH. The global quantities are:
T=4keV (in agreement with the velocity dispersion of 760km/s) and
. We cannot derive accurate gradients for these quantities with
our data, but there is strong evidence that the temperature is lower () and the metallicity much higher (Z ) in the very centre
(within about 50 1/h_50 kpc). We present a pixel by pixel method to model the
physical properties of the X-ray gas and derive its density distribution. We
apply classical methods to estimate the dynamical, gas and stellar masses, as
well as the cooling time and cooling flow characteristics. At the limiting
radius of the image (1.4 1/h_50 Mpc), we find _{\odot}M_{gas}/M_{Dyn}\sim 0.18 h_{50}^{-1.5}6.7\ 10^{12}M_{\odot}M/L_{V}\sim 300$.
The cooling time is estimated for different models, leading to a cooling radius
of 30-80 kpc depending on theComment: 14 pages incl 16 postscript figures available, 4 tables, corrected
stellar mass. Accepted for publication in Astronomy & Astrophysic
The rich cluster of galaxies ABCG 85. II. X-ray analysis using the ROSAT HRI
We present a new X-ray analysis mainly based on ROSAT HRI data. The HRI
spatial resolution combined with an improved wavelet analysis method and with
complementary radio and optical data provides new results compared to a
previous paper based on ROSAT PSPC data (Pislar et al. 1997). We use also
redshift data in order to identify galaxies dynamically belonging to the main
body of the cluster and/or to superimposed substructures. Various kinds of
emission are superimposed on a mean thermal X-ray emission due to the
intra-cluster gas: a) an X-ray flux excess in the centre; b) a south blob,
partially generated by individual galaxies. The mean velocity and velocity
dispersion of the galaxies located in this region are the same as those of the
cluster as a whole: it therefore does not seem to be a bound subgroup; c) West
emission due to a foreground group with self-emission from a Seyfert galaxy
located at the north-west; d) emission in the south-west due to inverse Compton
emission associated to a very steep radio source (the remnant of an active
galactic nucleus). We have examined the possibility for the central peak to be
an "unusual" galaxy, as assumed for the central galaxy of J2310-43 (Tananbaum
et al. 1997). We conclude on the existence of a cooling flow region, in which
the presence of at least three small features certainly related to cooler blobs
is revealed by the wavelet analysis. We have performed a pixel-to-pixel
modelling of the double X-ray emission. The large scale emission component is
comparable to those derived from by the PSPC data and the small scale one is
interpreted as a cooling-flow. A multiphase gas model analysis leads to a mass
deposit of 50-150 M_\odot/yr.Comment: 11 pages, 6 figures, 3 tables, LaTeX Accepted for publication in
Astronomy & Astrophysics main journa
Structure detection in the D1 CFHTLS deep field using accurate photometric redshifts: a benchmark
We investigate structures in the D1 CFHTLS deep field in order to test the
method that will be applied to generate homogeneous samples of clusters and
groups of galaxies in order to constrain cosmology and detailed physics of
groups and clusters. Adaptive kernel technique is applied on galaxy catalogues.
This technique needs none of the usual a-priori assumptions (luminosity
function, density profile, colour of galaxies) made with other methods. Its
main drawback (decrease of efficiency with increasing background) is overcame
by the use of narrow slices in photometric redshift space. There are two main
concerns in structure detection. One is false detection and the second, the
evaluation of the selection function in particular if one wants "complete"
samples. We deal here with the first concern using random distributions. For
the second, comparison with detailed simulations is foreseen but we use here a
pragmatic approach with comparing our results to GalICS simulations to check
that our detection number is not totally at odds compared to cosmological
simulations. We use XMM-LSS survey and secured VVDS redshifts up to z~1 to
check individual detections. We show that our detection method is basically
capable to recover (in the regions in common) 100% of the C1 XMM-LSS X-ray
detections in the correct redshift range plus several other candidates.
Moreover when spectroscopic data are available, we confirm our detections, even
those without X-ray data.Comment: 14 pages, 22 additionnal jpeg figures, accepted in A&
The Cluster of Galaxies Abell 970
We present a dynamical analysis of the galaxy cluster Abell 970 based on a
new set of radial velocities measured at ESO, Pic du Midi and Haute-Provence
observatories. Our analysis indicates that this cluster has a substructure and
is out of dynamical equilibrium. This conclusion is also supported by
differences in the positions of the peaks of the surface density distribution
and X-ray emission, as well as by the evidence of a large scale velocity
gradient in the cluster. We also found a discrepancy between the masses
inferred with the virial theorem and with the X-ray emission, what is expected
if the galaxies and the gas inside the cluster are not in hydrostatic
equilibrium. Abell 970 has a modest cooling flow, as is expected if it is out
of equilibrium as suggested by Allen (1998). We propose that cooling flows may
have an intermittent behavior, with phases of massive cooling flows being
followed by phases without significant cooling flows after the acretion of a
galaxy group massive enough to disrupt the dynamical equilibrium in the center
of the clusters. A massive cooling flow will be established again, after a new
equilibrium is achieved.Comment: 24 pages, 9 figures, submitted to A&
Commissioning of the vacuum system of the KATRIN Main Spectrometer
The KATRIN experiment will probe the neutrino mass by measuring the
beta-electron energy spectrum near the endpoint of tritium beta-decay. An
integral energy analysis will be performed by an electro-static spectrometer
(Main Spectrometer), an ultra-high vacuum vessel with a length of 23.2 m, a
volume of 1240 m^3, and a complex inner electrode system with about 120000
individual parts. The strong magnetic field that guides the beta-electrons is
provided by super-conducting solenoids at both ends of the spectrometer. Its
influence on turbo-molecular pumps and vacuum gauges had to be considered. A
system consisting of 6 turbo-molecular pumps and 3 km of non-evaporable getter
strips has been deployed and was tested during the commissioning of the
spectrometer. In this paper the configuration, the commissioning with bake-out
at 300{\deg}C, and the performance of this system are presented in detail. The
vacuum system has to maintain a pressure in the 10^{-11} mbar range. It is
demonstrated that the performance of the system is already close to these
stringent functional requirements for the KATRIN experiment, which will start
at the end of 2016.Comment: submitted for publication in JINST, 39 pages, 15 figure
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
Naturalizing action theory
The aim of this paper is to give a new argument for naturalized action theory. The sketch of the argument is the following: the immediate mental antecedents of actions, that is, the mental states that makes actions actions, are not normally accessible to introspection. But then we have no other option but to turn to the empirical sciences if we want to characterize and analyze them
Rapid Generation of MicroRNA Sponges for MicroRNA Inhibition
MicroRNA (miRNA) sponges are transcripts with repeated miRNA antisense sequences that can sequester miRNAs from endogenous targets. MiRNA sponges are valuable tools for miRNA loss-of-function studies both in vitro and in vivo. We developed a fast and flexible method to generate miRNA sponges and tested their efficiency in various assays. Using a single directional ligation reaction we generated sponges with 10 or more miRNA binding sites. Luciferase and AGO2-immuno precipitation (IP) assays confirmed effective binding of the miRNAs to the sponges. Using a GFP competition assay we showed that miR-19 sponges with central mismatches in the miRNA binding sites are efficient miRNA inhibitors while sponges with perfect antisense binding sites are not. Quantification of miRNA sponge levels suggests that this is at least in part due to degradation of the perfect antisense sponge transcripts. Finally, we provide evidence that combined inhibition of miRNAs of the miR-17∼92 cluster results in a more effective growth inhibition as compared to inhibition of individual miRNAs. In conclusion, we describe and validate a method to rapidly generate miRNA sponges for miRNA loss-of-function studies
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