86 research outputs found
ICM cooling, AGN feedback and BCG properties of galaxy groups-Five properties where groups differ from clusters
Using Chandra data for a sample of 26 galaxy groups, we constrained the
central cooling times (CCTs) of the ICM and classified the groups as strong
cool-core (SCC), weak cool-core (WCC) and non-cool-core (NCC) based on their
CCTs. The total radio luminosity of the brightest cluster galaxy (BCG) was
obtained using radio catalog data and literature, which was compared to the CCT
to understand the link between gas cooling and radio output. We determined
K-band luminosities of the BCG with 2MASS data, and used it to constrain the
masses of the SMBH, which were then compared to the radio output. We also
tested for correlations between the BCG luminosity and the overall X-ray
luminosity and mass of the group.
The observed cool-core/non-cool-core fractions for groups are comparable to
those of clusters. However, notable differences are seen. For clusters, all
SCCs have a central temperature drop, but for groups, this is not the case as
some SCCs have centrally rising temperature profiles. While for the cluster
sample, all SCC clusters have a central radio source as opposed to only 45% of
the NCCs, for the group sample, all NCC groups have a central radio source as
opposed to 77% of the SCC groups. For clusters, there are indications of an
anticorrelation trend between radio luminosity and CCT which is absent for the
groups. Indications of a trend of radio luminosity with black hole mass
observed in SCC clusters is absent for groups. The strong correlation observed
between the BCG luminosity and the cluster X-ray luminosity/cluster mass
weakens significantly for groups.
We conclude that there are important differences between clusters and groups
within the ICM cooling/AGN feedback paradigm.Comment: Accepted for publication in Astronomy and Astrophysic
The polytropic approximation and X-ray scaling relations: constraints on gas and dark matter profiles for galaxy groups and clusters
We constrain gas and dark matter (DM) parameters of galaxy groups and
clusters, by comparing X-ray scaling relations to theoretical expectations,
obtained assuming that the gas is in hydrostatic equilibrium with the DM and
follows a polytropic relation. We vary four parameters: the gas polytropic
index Gamma, its temperature at large radii T_xi, the DM logarithmic slope at
large radii zeta and its concentration c_vir. When comparing the model to the
observed mass-temperature (M-T) relation of local clusters, our results are
independent of both T_xi and c_vir. We thus obtain constraints on Gamma, by
fixing the DM profile, and on zeta, by fixing the gas profile. For an NFW DM
profile, we find that 6/5<Gamma<13/10, which is consistent with numerical
simulations and observations of individual clusters. Taking 6/5<Gamma<13/10
allows the DM profile to be slightly steeper than the NFW profile at large
radii. Upon including local groups, we constrain the mass-dependence of Gamma
and the value of T_xi. Interestingly, with Gamma=6/5 and zeta=-3, we reproduce
the observed steepening/breaking of the M-T relation at low M, if 10^6
K<T_xi<10^7 K, consistent with simulations and observations of the warm-hot
intergalactic medium. When extrapolated to high redshift z, the model with a
constant Gamma reproduces the expected self-similar behaviour. We also account
for the observed, non-self-similar relations provided by some high-z clusters,
as they provide constraints on the evolution of Gamma. Comparing our model to
the observed luminosity-temperature relation, we discriminate between different
M-c_vir relations: a weak dependence of c_vir on M is currently preferred by
data. This simple theoretical model accounts for much of the complexity of
recent, improved X-ray scaling relations, provided that we allow for a mild
dependence of Gamma on M or for T_xi consistent with intercluster values.
[abridged]Comment: 20 pages, 18 figures, 2 tables. Accepted for publication in MNRAS,
with minor changes. Accepted version plus two typos corrected. Abstract
abridged for astro-ph submissio
The nature of the unresolved extragalactic soft CXB
In this paper we investigate the power spectrum of the unresolved 0.5-2 keV
CXB with deep Chandra 4 Ms observations in the CDFS. We measured a signal
which, on scales >30", is significantly higher than the Shot-Noise and is
increasing with the angular scale. We interpreted this signal as the joint
contribution of clustered undetected sources like AGN, Galaxies and
Inter-Galactic-Medium (IGM). The power of unresolved cosmic sources
fluctuations accounts for \sim 12% of the 0.5-2 keV extragalactic CXB. Overall,
our modeling predicts that \sim 20% of the unresolved CXB flux is made by low
luminosity AGN, \sim 25% by galaxies and \sim 55% by the IGM (Inter Galactic
Medium). We do not find any direct evidence of the so called Warm Hot
Intergalactic Medium (i.e. matter with 10^5K<T<10^7K and density contrast
{\delta} <1000), but we estimated that it could produce about 1/7 of the
unresolved CXB. We placed an upper limit to the space density of postulated
X-ray-emitting early black hole at z>7.5 and compared it with SMBH evolution
models.Comment: 15 pages, 9 figures, accepted by MNRA
Non-parametric modeling of the intra-cluster gas using APEX-SZ bolometer imaging data
We demonstrate the usability of mm-wavelength imaging data obtained from the
APEX-SZ bolometer array to derive the radial temperature profile of the hot
intra-cluster gas out to radius r_500 and beyond. The goal is to study the
physical properties of the intra-cluster gas by using a non-parametric
de-projection method that is, aside from the assumption of spherical symmetry,
free from modeling bias. We use publicly available X-ray imaging data from the
XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data
from the APEX-SZ experiment at 150 GHz to de-project the density and
temperature profiles for the relaxed cluster Abell 2204. We derive the gas
density, temperature and entropy profiles assuming spherical symmetry, and
obtain the total mass profile under the assumption of hydrostatic equilibrium.
For comparison with X-ray spectroscopic temperature models, a re-analysis of
the recent Chandra observation is done with the latest calibration updates.
Using the non-parametric modeling we demonstrate a decrease of gas temperature
in the cluster outskirts, and also measure the gas entropy profile. These
results are obtained for the first time independently of X-ray spectroscopy,
using SZE and X-ray imaging data. The contribution of the SZE systematic
uncertainties in measuring T_e at large radii is shown to be small compared to
the Chandra systematic spectroscopic errors. The upper limit on M_200 derived
from the non-parametric method is consistent with the NFW model prediction from
weak lensing analysis.Comment: Replaced with the published version; A&A 519, A29 (2010
The MUSIC of Galaxy Clusters II: X-ray global properties and scaling relations
We present the X-ray properties and scaling relations of a large sample of clusters extracted from the Marenostrum MUltidark SImulations of galaxy Clusters (MUSIC) data set. We focus on a sub-sample of 179 clusters at redshift z similar to 0.11, with 3.2 x 10(14) h(-1) M-circle dot < M-vir < 2 x 10(15) h(-1) M-circle dot, complete in mass. We employed the X-ray photon simulator PHOX to obtain synthetic Chandra observations and derive observable-like global properties of the intracluster medium (ICM), as X-ray temperature (T-X) and luminosity (L-X). T-X is found to slightly underestimate the true mass-weighted temperature, although tracing fairly well the cluster total mass. We also study the effects of T-X on scaling relations with cluster intrinsic properties: total (M-500 and gas M-g,M-500 mass; integrated Compton parameter (Y-SZ) of the Sunyaev-Zel'dovich (SZ) thermal effect; Y-X = M-g,M-500 T-X. We confirm that Y-X is a very good mass proxy, with a scatter on M-500-Y-X and Y-SZ-Y-X lower than 5 per cent. The study of scaling relations among X-ray, intrinsic and SZ properties indicates that simulated MUSIC clusters reasonably resemble the self-similar prediction, especially for correlations involving T-X. The observational approach also allows for a more direct comparison with real clusters, from which we find deviations mainly due to the physical description of the ICM, affecting T-X and, particularly, L-X
Visuomotor Cerebellum in Human and Nonhuman Primates
In this paper, we will review the anatomical components of the visuomotor cerebellum in human and, where possible, in non-human primates and discuss their function in relation to those of extracerebellar visuomotor regions with which they are connected. The floccular lobe, the dorsal paraflocculus, the oculomotor vermis, the uvula–nodulus, and the ansiform lobule are more or less independent components of the visuomotor cerebellum that are involved in different corticocerebellar and/or brain stem olivocerebellar loops. The floccular lobe and the oculomotor vermis share different mossy fiber inputs from the brain stem; the dorsal paraflocculus and the ansiform lobule receive corticopontine mossy fibers from postrolandic visual areas and the frontal eye fields, respectively. Of the visuomotor functions of the cerebellum, the vestibulo-ocular reflex is controlled by the floccular lobe; saccadic eye movements are controlled by the oculomotor vermis and ansiform lobule, while control of smooth pursuit involves all these cerebellar visuomotor regions. Functional imaging studies in humans further emphasize cerebellar involvement in visual reflexive eye movements and are discussed
Hot atmospheres of galaxies, groups, and clusters of galaxies
Most of the ordinary matter in the local Universe has not been converted into
stars but resides in a largely unexplored diffuse, hot, X-ray emitting plasma.
It pervades the gravitational potentials of massive galaxies, groups and
clusters of galaxies, as well as the filaments of the cosmic web. The physics
of this hot medium, such as its dynamics, thermodynamics and chemical
composition can be studied using X-ray spectroscopy in great detail. Here, we
present an overview of the basic properties and discuss the self similarity of
the hot "atmospheres" permeating the gravitational halos from the scale of
galaxies, through groups, to massive clusters. Hot atmospheres are stabilised
by the activity of supermassive black holes and, in many ways, they are of key
importance for the evolution of their host galaxies. The hot plasma has been
significantly enriched in heavy elements by supernovae during the period of
maximum star formation activity, probably more than 10 billion years ago. High
resolution X-ray spectroscopy just started to be able to probe the dynamics of
atmospheric gas and future space observatories will determine the properties of
the currently unseen hot diffuse medium throughout the cosmic web.Comment: Accepted for publication in the book "Reviews in Frontiers of Modern
Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka;
publisher Springer Nature) funded by the European Union Erasmus+ Strategic
Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-03556
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