1,293 research outputs found
A2163: Merger events in the hottest Abell galaxy cluster II. Subcluster accretion with galaxy-gas separation
Located at z = 0.203, A2163 is a rich galaxy cluster with an intra-cluster
medium (ICM) that exhibits extraordinary properties, including an exceptionally
high X-ray luminosity, average temperature, and a powerful and extended radio
halo. The irregular and complex morphology of its gas and galaxy structure
suggests that this cluster has recently undergone major merger events that
involve two or more cluster components. In this paper, we study the gas
structure and dynamics by means of spectral-imaging analysis of X-ray data
obtained from XMM-Newton and Chandra observations. From the evidence of a cold
front, we infer the westward motion of a cool core across the E-W elongated
atmosphere of the main cluster A2163-A. Located close to a galaxy over-density,
this gas 'bullet' appears to have been spatially separated from its galaxy (and
presumably dark matter component) as a result of high-velocity accretion.
From gas brightness and temperature profile analysis performed in two
opposite regions of the main cluster, we show that the ICM has been
adiabatically compressed behind the crossing 'bullet' possibly because of shock
heating, leading to a strong departure of the ICM from hydrostatic equilibrium
in this region. Assuming that the mass estimated from the Yx proxy best
indicates the overall mass of the system and that the western cluster sector is
in approximate hydrostatic equilibrium before subcluster accretion, we infer a
merger scenario between two subunits of mass ratio 1:4, leading to a present
total system mass of M500 . The exceptional
properties of A2163 present various similarities with those of 1E0657-56, the
so-called 'bullet-cluster'. These similarities are likely to be related to a
comparable merger scenario.Comment: A&A, in pres
The XMM-LSS survey: the Class 1 cluster sample over the extended 11 deg and its spatial distribution
This paper presents 52 X-ray bright galaxy clusters selected within the 11
deg XMM-LSS survey. 51 of them have spectroscopic redshifts
(), one is identified at , and all together make
the high-purity "Class 1" (C1) cluster sample of the XMM-LSS, the highest
density sample of X-ray selected clusters with a monitored selection function.
Their X-ray fluxes, averaged gas temperatures (median keV),
luminosities (median ergs/s) and total mass
estimates (median ) are measured, adapting to
the specific signal-to-noise regime of XMM-LSS observations. The redshift
distribution of clusters shows a deficit of sources when compared to the
cosmological expectations, regardless of whether WMAP-9 or Planck-2013 CMB
parameters are assumed. This lack of sources is particularly noticeable at . However, after quantifying uncertainties due to small
number statistics and sample variance we are not able to put firm (i.e. ) constraints on the presence of a large void in the cluster
distribution. We work out alternative hypotheses and demonstrate that a
negative redshift evolution in the normalization of the relation
(with respect to a self-similar evolution) is a plausible explanation for the
observed deficit. We confirm this evolutionary trend by directly studying how
C1 clusters populate the space, properly accounting for selection
biases. We point out that a systematically evolving, unresolved, central
component in clusters and groups (AGN contamination or cool core) can impact
the classification as extended sources and be partly responsible for the
observed redshift distribution.[abridged]Comment: 33 pages, 21 figures, 3 tables ; accepted for publication in MNRA
Nanosized superconducting constrictions
Nanowires of lead between macroscopic electrodes are produced by means of an
STM. Magnetic fields may destroy the superconductivity in the electrodes, while
the wire remains in the superconducting state. The properties of the resulting
microscopic Josephson junctions are investigated.Comment: 3 pages,3 eps figures include
Molecular gas in Low Luminosity Radio Galaxies in (proto-)clusters at z~0.4-2.6
We investigate the role of the environment in processing molecular gas in radio galaxies (RGs). We observed five RGs at z=0.4-2.6 in dense Mpc-scale environment with the IRAM-30m telescope. We set four upper-limits and report a tentative CO(7-6) detection at signal-to-noise ratio SNR>~2 for COSMOS-FRI~70, at z=2.63. If the detection will be confirmed at higher SNR, COSMOS-FRI~70 will become the most distant brightest cluster galaxy (BCG) candidate detected in CO. We speculate that the cluster environment might have played a role in preventing the refueling via environmental mechanisms such as galaxy harassment, strangulation, ram-pressure, or tidal stripping. The RGs of this work are excellent targets for ALMA as well as next generation telescopes such as the James Webb Space Telescope
Dynamical segregation of galaxies in groups and clusters
We have performed a systematic analysis of the dynamics of different galaxy
populations in galaxy groups from the 2dFGRS. For this purpose we have combined
all the groups into a single system, where velocities v and radius r are
expressed adimensionally. We have used several methods to compare the
distributions of relative velocities of galaxies with respect to the group
centre for samples selected according to their spectral type (as defined by
Madgwick et al., 2002), bj band luminosity and B-R colour index. We have found
strong segregation effects: spectral type I objects show a statistically
narrower velocity distribution than that of galaxies with a substantial star
formation activity (type II-IV). Similarly, the same behavior is observed for
galaxies with colour index B-R>1 compared to galaxies with B-R<1. Bright
(Mb-19) galaxies show the same segregation. It is not
important once the sample is restricted to a given spectral type. These effects
are particularly important in the central region (Rp<Rvirial/2) and do not have
a strong dependence on the mass of the parent group. These trends show a strong
correlation between the dynamics of galaxies in groups and star formation rate
reflected both by spectral type and by colour index.Comment: 7 pages, 8 figures. Accepted for publication in MNRA
Exposure to androstenes influences processing of emotional words
There is evidence that human-produced androstenes affect attitudinal, emotional, and physiological states in a context-dependent manner, suggesting that they could be involved in modulating social interactions. For instance, androstadienone appears to increase attention specifically to emotional information. Most of the previous work focused on one or two androstenes. Here, we tested whether androstenes affect linguistic processing, using three different androstene compounds. Participants (90 women and 77 men) performed a lexical decision task after being exposed to an androstene or to a control treatment (all compounds were applied on the philtrum). We tested effects on three categories of target words, varying in emotional valence: positive, competitive, and neutral words (e.g., hope, war, and century, respectively). Results show that response times were modulated by androstene treatment and by emotional valence of words. Androstenone, but not androstadienone and androstenol, significantly slowed down the reaction time to words with competitive valence. Moreover, men exposed to androstenol showed a significantly reduced error rate, although men tended to make more errors than women in general. This suggests that these androstenes modulate the processing of emotional words, namely some particular lexical emotional content may become more salient under the effect of androstenes
A refined stable restriction theorem for vector bundles on quadric threefolds
Let E be a stable rank 2 vector bundle on a smooth quadric threefold Q in the
projective 4-space P. We show that the hyperplanes H in P for which the
restriction of E to the hyperplane section of Q by H is not stable form, in
general, a closed subset of codimension at least 2 of the dual projective
4-space, and we explicitly describe the bundles E which do not enjoy this
property. This refines a restriction theorem of Ein and Sols [Nagoya Math. J.
96, 11-22 (1984)] in the same way the main result of Coanda [J. reine angew.
Math. 428, 97-110 (1992)] refines the restriction theorem of Barth [Math. Ann.
226, 125-150 (1977)].Comment: Ann. Mat. Pura Appl. 201
Lack of Foxp3 function and expression in the thymic epithelium
Foxp3 is essential for the commitment of differentiating thymocytes to the regulatory CD4+ T (T reg) cell lineage. In humans and mice with a genetic Foxp3 deficiency, absence of this critical T reg cell population was suggested to be responsible for the severe autoimmune lesions. Recently, it has been proposed that in addition to T reg cells, Foxp3 is also expressed in thymic epithelial cells where it is involved in regulation of early thymocyte differentiation and is required to prevent autoimmunity. Here, we used genetic tools to demonstrate that the thymic epithelium does not express Foxp3. Furthermore, we formally showed that genetic abatement of Foxp3 in the hematopoietic compartment, i.e. in T cells, is both necessary and sufficient to induce the autoimmune lesions associated with Foxp3 loss. In contrast, deletion of a conditional Foxp3 allele in thymic epithelial cells did not result in detectable changes in thymocyte differentiation or pathology. Therefore, in mice the only known role for Foxp3 remains promotion of T reg cell differentiation within the T cell lineage, whereas there is no role for Foxp3 in thymic epithelial cells
Vortex matter in superconducting mesoscopic disks: Structure, magnetization, and phase transitions
The dense vortex matter structure and associated magnetization are calculated
for type-II superconducting mesoscopic disks. The magnetization exhibits
generically first-order phase transitions as the number of vortices changes by
one and presents two well-defined regimes: A non-monotonous evolution of the
magnitude of the magnetization jumps signals the presence of a vortex glass
structure which is separated by a second-order phase transition at
from a condensed state of vortices (giant vortex) where the magnitude of the
jumps changes monotonously. We compare our results with Hall magnetometry
measurements by Geim et al. (Nature 390, 259 (1997)) and claim that the
magnetization exhibits clear traces of the presence of these vortex glass
states.Comment: 4 pages, 3 figure
Compensated right ventricular function of the onset of pulmonary hypertension in a rat model depends on chamber remodeling and contractile augmentation.
Right-ventricular function is a good indicator of pulmonary arterial hypertension (PAH) prognosis; however, how the right ventricle (RV) adapts to the pressure overload is not well understood. Here, we aimed at characterizing the time course of RV early remodeling and discriminate the contribution of ventricular geometric remodeling and intrinsic changes in myocardial mechanical properties in a monocrotaline (MCT) animal model. In a longitudinal study of PAH, ventricular morphology and function were assessed weekly during the first four weeks after MCT exposure. Using invasive measurements of RV pressure and volume, heart performance was evaluated at end of systole and diastole to quantify contractility (end-systolic elastance) and chamber stiffness (end-diastolic elastance). To distinguish between morphological and intrinsic mechanisms, a computational model of the RV was developed and used to determine the level of prediction when accounting for wall masses and unloaded volume measurements changes. By four weeks, mean pulmonary arterial pressure and elastance rose significantly. RV pressures rose significantly after the second week accompanied by significant RV hypertrophy, but RV stroke volume and cardiac output were maintained. The model analysis suggested that, after two weeks, this compensation was only possible due to a significant increase in the intrinsic inotropy of RV myocardium. We conclude that this MCT-PAH rat is a model of RV compensation during the first month after treatment, where geometric remodeling on EDPVR and increased myocardial contractility on ESPVR are the major mechanisms by which stroke volume is preserved in the setting of elevated pulmonary arterial pressure. The mediators of this compensation might themselves promote longer-term adverse remodeling and decompensation in this animal model
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