1,151 research outputs found
Deep ROSAT-HRI observation of the elliptical galaxy NGC 1399
We present the preliminary results of a deep (167 ks) ROSAT HRI observation
of the cD galaxy NGC1399 in the Fornax cluster. We find, in agreement with
previous observations, an extended (41 Kpc adopting a distance of 19 Mpc)
gaseous halo with a luminosity of L_X=(4.41\pm 0.04)x10^{41} erg/s. The 5
arcsec resolution of the data allows us to detect a very complex and asymmetric
structure of the halo with respect to the optical galaxy. Moreover the analysis
of the radial structure reveals the presence of a multi-component profile not
consistent with a simple King model over the whole 40 Kpc. We do not detect the
presence of a central source and pose an upper limit to the luminosity of a
possible active nucleus. Due to the length of the observation, comparable to
that of a deep survey, we detect a large number of sources within the HRI FOV,
in slight excess with respect to the estimates based on previous surveys. We
study the flux distribution of the sources, their temporal behaviour and their
spatial distribution with respect to the central galaxy.Comment: 15 pages, 10 figures (6 in color), 1 table; uses subfigure.sty,
supertabular.sty, lscape.sty, color.sty; To be published in the proceeding of
"X-ray Astronomy 2000" (Mondello (Palermo), September 2000
A kinematically decoupled component in NGC4778
We present a kinematical and photometrical study of a member, NGC4778, of the
nearest (z=0.0137) compact group: Hickson 62. Our analysis reveals that Hickson
62a, also known as NGC4778, is an S0 galaxy with kinematical and morphological
peculiarities, both in its central regions (r < 5'') and in the outer halo. In
the central regions, the rotation curve shows the existence of a kinematically
decoupled stellar component, offset with respect to the photometric center. In
the outer halo we find an asymmetric rotation curve and a velocity dispersion
profile showing a rise on the SW side, in direction of the galaxy NGC4776.Comment: Proceedings of the first workshop of astronomy and astrophysics for
student
Steps toward a classifier for the Virtual Observatory. I. Classifying the SDSS photometric archive
Modern photometric multiband digital surveys produce large amounts of data
that, in order to be effectively exploited, need automatic tools capable to
extract from photometric data an objective classification. We present here a
new method for classifying objects in large multi-parametric photometric data
bases, consisting of a combination of a clustering algorithm and a cluster
agglomeration tool. The generalization capabilities and the potentialities of
this approach are tested against the complexity of the Sloan Digital Sky Survey
archive, for which an example of application is reported.Comment: To appear in the Proceedings of the "1st Workshop of Astronomy and
Astrophysics for Students" - Naples, 19-20 April 200
The Luminosity Function of 81 Abell Clusters from the CRoNaRio catalogues
We present the composite luminosity function (hereafter LF) of galaxies for
81 Abell clusters studied in our survey of the Northern Hemisphere, using DPOSS
data processed by the CRoNaRio collaboration. The derived LF is very accurate
due to the use of homogeneous data both for the clusters and the control fields
and to the local estimate of the background, which takes into account the
presence of large-scale structures and of foreground clusters and groups. The
global composite LF is quite flat down to has a slope
with minor variations from blue to red filters, and
mag ( km s Mpc) in the
and filters, respectively (errors are detailed in the text). We find a
significant difference between rich and poor clusters thus arguing in favour of
a dependence of the LF on the properties of the environment.Comment: 8 pages, 5 figures. Contribution to the IAP 2000 Conference
"Constructing the Universe with Clusters of Galaxies", Paris, July 200
Morphology of low-redshift compact galaxy clusters I. Shapes and radial profiles
The morphology of clusters of galaxies may be described with a set of
parameters which contain information about the formation and evolutionary
history of these systems. In this paper we present a preliminary study of the
morphological parameters of a sample of 28 compact Abell clusters extracted
from DPOSS data. The morphology of galaxy clusters is parameterized by their
apparent ellipticity, position angle of the major axis, centre coordinates,
core radius and beta-model power law index. Our procedure provides estimates of
these parameters by simultaneously fitting them all, overcoming some of the
difficulties induced by sparse data and low number statistics typical of this
kind of analysis. The cluster parameters were fitted in a 3 x 3 h^-2 sqMpc
region, measuring the background in a 2 <R< 2.5 h^-1Mpc annulus. We also
explore the correlations between shape and profile parameters and other cluster
properties. One third of this compact cluster sample has core radii smaller
than 50 h^-1 kpc, i.e. near the limit that our data allow us to resolve,
possibly consistent with cusped models. The remaining clusters span a broad
range of core radii up to 750 h^-1 kpc. More than 80 per cent of this sample
has ellipticity higher than 0.2. The alignment between the cluster and the
major axis of the dominant galaxy is confirmed, while no correlation is
observed with other bright cluster members. No significant correlation is found
between cluster richness and ellipticity. Instead, cluster richness is found to
correlate, albeit with large scatter, with the cluster core radius.[abridged]Comment: 23 pages, 17 figures, accepted for publication in MNRAS. Full paper
including full resolution figures 2 and 9 at
http://www.eso.org/~vstrazzu/P/ME1030fv.pd
Impianto multifunzionale per la preparazione e l'imballaggio di passata di pomodoro, salse pronte, confettura e succhi di frutta.
Probing the Low Mass X-ray Binaries/Globular Cluster connection in NGC1399
We present a wide field study of the Globular Clusters/Low Mass X-ray
Binaries connection in the cD elliptical NGC1399, combining HST/ACS and Chandra
high resolution data. We find evidence that LMXB formation likelihood is
influenced by GCs structural parameters, in addition to the well known effects
of mass and metallicity, independently from galactocentric distance.Comment: in press in the Proceedings of the X-ray 2009 Conference, 7-11
September 2009, Bologna, Ital
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