48 research outputs found
X-ray Statistical Properties of the Central Cool Component in Clusters of Galaxies
Central cool gas component that is often observed from a well-relaxed cluster
system has long been interpreted as a consequence of ``Cooling Flow'' (CF),
radiative cooling followed by inflow of Intra-Cluster Medium (ICM). However,
recent XMM-Newton spectroscopy has shown no signatures of cooler gas phases
below certain temperatures in typical CF clusters (A1795, Tamura et al. 2001;
A1835, Peterson et al. 2001). This contradicts the conventional CF model or at
least requires a major revision of the model. In order to investigate
statistical properties of the central cool component, we performed systematic
analysis of ASCA data on 85 clusters. We found that 1) temperature of the
central cool component strongly depends on the temperature of the main ICM, 2)
the cool component is selectively found around a brightest cluster galaxy (BCG)
that coincide with the X-ray peak position, and 3) the luminosity-temperature
(L-T) relation of the cool component shows nice agreement with the L-T relation
of the main ICM. Together with the previous observational fact that, in some of
the ``CF'' clusters, the total gravitating mass is clustering in two distinct
spatial scales, a main cluster component and a second small-scale system, we
conclude that the central cool component is associated with the second
small-scale self-gravitating system that is immersed in the host cluster, and
the cool component temperature reflects the gravitational potential depth.Comment: Proceedings of "Tracing Cosmic Evolution with Clusters of Galaxies",
Sesto Pusteria, Bolzano, Italy, July 3-6, 200
The eigenvalue problem for infinite compact complex symmetric matrices with application to the numerical computation of complex zeros of J0(z) − iJ1(z) and of Bessel functions Jm(z) of any real order m
AbstractConsider computing simple eigenvalues of a given compact infinite matrix re- garded as operating in the complex Hilbert space l2 by computing the eigenvalues of the truncated finite matrices and taking an obvious limit. In this paper we deal with a special case where the given matrix is compact, complex, and symmetric (but not necessarily Hermitian). Two examples of application are studied. The first is con- cerned with the equation J0(z) − iJ1(z)=0 appearing in the analysis of the solitary-wave runup on a sloping beach, and the second with the zeros of the Bessel function Jm(z) of any real order m. In each case, the problem is reformulated as an eigenvalue problem for a compact complex symmetric tridiagonal matrix operator in l2 whose eigenvalues are all simple. A complete error analysis for the numerical solution by truncation is given, based on the general theorems proved in this paper, where the usefulness of the seldom used generalized Rayleigh quotient is demonstrated
X-ray Measurements of the Gravitational Potential Profile in the Central Region of the Abell 1060 Cluster of Galaxies
X-ray spectral and imaging data from ASCA and ROSAT were used to measure the
total mass profile in the central region of Abell 1060, a nearby and relatively
poor cluster of galaxies. The ASCA X-ray spectra, after correcting for the
spatial response of the X-ray telescope, show an isothermal distribution of the
intra-cluster medium (ICM) within at least 12' (or kpc;
km sMpc) in radius of the cluster center. The
azimuthally averaged surface brightness profile from the ROSAT PSPC exhibits a
central excess above an isothermal model. The ring-sorted ASCA GIS
spectra and the radial surface brightness distribution from the ROSAT PSPC were
simultaneously utilized to constrain the gravitational potential profile. Some
analytic models of the total mass density profile were examined. The ICM
density profile was also specified by analytic forms. The ICM temperature
distribution was constrained to satisfy the hydrostatic equilibrium, and to be
consistent with the data. Then, the total mass distribution was found to be
described better by the universal dark halo profile proposed by Navarro, Frenk,
and White (1996;1997) than by a King-type model with a flat density core. A
profile with a central cusp together with a logarithmic radial slope of was also consistent with the data. Discussions are made concerning the
estimated dark matter distribution around the cluster center.Comment: 32 pages. Accepted: ApJ 2000, 35 pages, Title was correcte
X-ray observations of the rich cluster CL 0939+4713 and discovery of the strongly variable source RXJ0943.0+4701
Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795
Using the X-ray data from \ASCA, spectral and spatial properties of the
intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a
radial distance of ( kpc). The ICM
temperature and abundance are spatially rather constant, although the cool
emission component is reconfirmed in the central region. The azimuthally-
averaged radial X-ray surface brightness profiles are very similar between soft
(0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with
a single- model due to a strong data excess within of the
cluster center. In contrast, double- models can successfully reproduce
the overall brightness profiles both in the soft and hard energy bands, as well
as that derived with the \ROSAT PSPC. Properties of the central excess
brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT
and \ASCA. Thus, the excess X-ray emission from the core region of this cluster
is confirmed for the first time in hard X-rays above 3 keV. This indicates that
the shape of the gravitational potential becomes deeper than the King-type one
towards the cluster center. Radial profiles of the total gravitating matter,
calculated using the double- model, reveal an excess mass of within kpc of the cluster
center. This suggests a hierarchy in the gravitational potential corresponding
to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998
Largely Extended X-ray Emission around the Elliptical Galaxy NGC 4636 Observed with ASCA
ASCA observations of NGC 4636 and a southern region have revealed extended
X-ray emission to a radius of about 300 kpc from the galaxy. The symmetric
nature of the observed surface brightness around NGC 4636 indicates its
association to this galaxy rather than to the Virgo cluster. Model independent
estimation of the gravitational mass profile shows a flattening at a radius of
kpc, where the total mass reaches
and a mass-to-light ratio of 23. The mass still increases to larger radii,
reaching with a mass-to-light ratio of 300 at
300 kpc from NGC 4636. These features suggest presence of a galaxy group
surrounding NGC 4636. If such optically dark groups are common among X-ray
bright ellipticals, it would explain the very large scatter in their X-ray
luminosities with similar optical luminosities.Comment: 14 pages with 3 figures, AAS Latex, accepted to ApJ
X-ray Measurement of Dark Matter "Temperature" in Abell 1795
We present a method from an X-ray observation of a galaxy cluster to measure
the radial profile of the dark matter velocity dispersion, sigma_DM, and to
compare the dark matter ``temperature'' defined as mu m_p sigma_DM**2 / k_B
with the gas temperature. The method is applied to the XMM-Newton observation
of Abell 1795. The ratio between the specific energy of the dark matter and
that of the intracluster medium (ICM), which can be defined as beta_DM in
analogy with beta_spec, is found to be less than unity everywhere ranging
\~0.3-0.8. In other words, the ICM temperature is higher than the dark matter
``temperature'', even in the central region where the radiative cooling time is
short. A beta_DM value smaller than unity can most naturally be explained by
heating of the ICM. The excess energy of ICM is estimated to be ~1-3 keV per
particle.Comment: ApJ in pres
Variantes genéticas en el locus 9p21 contribuyen al desarrollo de arteriosclerosis a través de la modulación de ANRIL y CDKN2A/B
Registro creado en correspondencia al grado de doctora de Ada Congrains Castillo.Los estudios de asociación de todo el genoma (GWAS) han identificado variantes genéticas que contribuyen al riesgo de enfermedad cardiovascular (ECV) en el locus del cromosoma 9p21. La región asociada a CVD es adyacente a los dos inhibidores de quinasas dependientes de ciclina (CDKN) 2A y 2B y los últimos exones del ARN no codificante, ANRIL. Todavía no está claro cuál de estas transcripciones o cómo están involucradas en la patogénesis de la aterosclerosis.Genome-wide association studies (GWAS) have identified genetic variants contributing to the risk of cardiovascular disease (CVD) at the chromosome 9p21 locus. The CVD-associated region is adjacent to the two cyclin dependent kinase inhibitors (CDKN)2A and 2B and the last exons of the non-coding RNA, ANRIL. It is still not clear which of or how these transcripts are involved in the pathogenesis of atherosclerosis.Japón. Programa de Promoción de Estudios Fundamentales en el Instituto Nacional de Innovación Biomédica de Japón
(HR: 22-2-5), el Ministerio de Educación, Cultura, Deportes, Ciencia y Tecnología de
Japón (KK: 22510211) y la Fundación NOVARTIS para la Investigación Gerontológica (KK).Tesi