510 research outputs found
On the role of AGN feedback on the thermal and chemodynamical properties of the hot intra-cluster medium
We present an analysis of the properties of the ICM in an extended set of
cosmological hydrodynamical simulations of galaxy clusters and groups performed
with the TreePM+SPH GADGET-3 code. Besides a set of non-radiative simulations,
we carried out two sets of simulations including radiative cooling, star
formation, metal enrichment and feedback from supernovae, one of which also
accounts for the effect of feedback from AGN resulting from gas accretion onto
super-massive black holes. These simulations are analysed with the aim of
studying the relative role played by SN and AGN feedback on the general
properties of the diffuse hot baryons in galaxy clusters and groups: scaling
relations, temperature, entropy and pressure radial profiles, and ICM chemical
enrichment. We find that simulations including AGN feedback produce scaling
relations that are in good agreement with X-ray observations at all mass
scales. However, our simulations are not able to account for the observed
diversity between CC and NCC clusters: unlike for observations, we find that
temperature and entropy profiles of relaxed and unrelaxed clusters are quite
similar and resemble more the observed behaviour of NCC clusters. As for the
pattern of metal enrichment, we find that an enhanced level of iron abundance
is produced by AGN feedback with respect to the case of purely SN feedback. As
a result, while simulations including AGN produce values of iron abundance in
groups in agreement with observations, they over-enrich the ICM in massive
clusters. The efficiency of AGN feedback in displacing enriched gas from halos
into the inter-galactic medium at high redshift also creates a widespread
enrichment in the outskirts of clusters and produces profiles of iron abundance
whose slope is in better agreement with observations.Comment: 23 pages, 14 figures, 1 table, accepted for publication in MNRA
Cool Core Clusters from Cosmological Simulations
We present results obtained from a set of cosmological hydrodynamic
simulations of galaxy clusters, aimed at comparing predictions with
observational data on the diversity between cool-core (CC) and non-cool-core
(NCC) clusters. Our simulations include the effects of stellar and AGN feedback
and are based on an improved version of the smoothed particle hydrodynamics
code GADGET-3, which ameliorates gas mixing and better captures gas-dynamical
instabilities by including a suitable artificial thermal diffusion. In this
Letter, we focus our analysis on the entropy profiles, the primary diagnostic
we used to classify the degree of cool-coreness of clusters, and on the iron
profiles. In keeping with observations, our simulated clusters display a
variety of behaviors in entropy profiles: they range from steadily decreasing
profiles at small radii, characteristic of cool-core systems, to nearly flat
core isentropic profiles, characteristic of non-cool-core systems. Using
observational criteria to distinguish between the two classes of objects, we
find that they occur in similar proportions in both simulations and in
observations. Furthermore, we also find that simulated cool-core clusters have
profiles of iron abundance that are steeper than those of NCC clusters, which
is also in agreement with observational results. We show that the capability of
our simulations to generate a realistic cool-core structure in the cluster
population is due to AGN feedback and artificial thermal diffusion: their
combined action allows us to naturally distribute the energy extracted from
super-massive black holes and to compensate for the radiative losses of
low-entropy gas with short cooling time residing in the cluster core.Comment: 6 pages, 4 figures, accepted in ApJL, v2 contains some modifications
on the text (results unchanged
Energetic study of cardioplegic hearts under ischaemia/reperfusion and [Ca2+] changes in cardiomyocytes of guinea-pig: Mitochondrial role
Abstract Aim: To study the role of mitochondria in the recovery of guinea-pig hearts exposed to high-K+-cardioplegia (CPG) and ischaemia/reperfusion (I/R) Methods: We measured contractility and heat release in perfused guineapig hearts and cytosolic and mitochondrial Ca2+ by epifluorescence and confocal microscopy in isolated cardiomyocytes loaded with Fluo-4 or Rhod-2. Results: In hearts, CPG increased the postischaemic contractile recovery, and this was potentiated by the mNCX blocker clonazepam and the mKATP opener diazoxide, which also prevented the fall in muscle economy. Moreover, CPG prevented the stunning induced by ouabain, which was reduced by clonazepam. In cardiomyocytes, CPG increased fluorescent signals of cytosolic and mitochondrial Ca2+, while the addition of a mNCX blocker (CGP37157) increased cytosolic but reduced mitochondrial [Ca2+]. Ouabain in CPG increased cytosolic Ca2+ and resting heat, but the addition of CGP37157 reduced them, as well as mitochondrial Ca2+. Conclusions: CPG, diazoxide and clonazepam improve postischaemic recovery, respectively, by increasing the Ca2+ cycling and by reducing the mitochondrial Ca2+ uptake either by uniporter or by mNCX. The mitochondria compete with the leaky sarcoplasmic reticulum (SR) as sink of Ca2+ in guinea-pig hearts, affecting the postischaemic contractility. CPG also prevented the ouabain-induced dysfunction by avoiding the Ca2+ overload. Ouabain reduced the synergism between CPG and clonazepam suggesting that [Na+]i and SR load influence the mNCX role.Fil: Ragone, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Ciencias Biológicas. Cátedra de Farmacología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Torres, N. S.. Cardiovascular Research And Training Institute; Estados UnidosFil: Consolini, A. E.. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Ciencias Biológicas. Cátedra de Farmacología; Argentin
AdipoRon and Pancreatic Ductal Adenocarcinoma: a future perspective in overcoming chemotherapy-induced resistance?
The Halo Mass-Bias Redshift Evolution in the CDM Cosmology
We derive an analytic model for the redshift evolution of linear-bias,
allowing for interactions and merging of the mass-tracers, by solving a second
order differential equation based on linear perturbation theory and the
Friedmann-Lemaitre solutions of the cosmological field equations. We then study
the halo-mass dependence of the bias evolution, using the dark matter halo
distribution in a CDM simulation in order to calibrate the free
parameters of the model. Finally, we compare our theoretical predictions with
available observational data and find a good agreement. In particular, we find
that the bias of optical QSO's evolve differently than those selected in X-rays
and that their corresponding typical dark matter halo mass is and \magcir 5 \times 10^{13} h^{-1} M_{\odot},
respectively.Comment: 8 pages, 5 figures, accepted for publication in Ap
Cosmological hydrodynamical simulations of galaxy clusters: X-ray scaling relations and their evolution
We analyse cosmological hydrodynamical simulations of galaxy clusters to
study the X-ray scaling relations between total masses and observable
quantities such as X-ray luminosity, gas mass, X-ray temperature, and .
Three sets of simulations are performed with an improved version of the
smoothed particle hydrodynamics GADGET-3 code. These consider the following:
non-radiative gas, star formation and stellar feedback, and the addition of
feedback by active galactic nuclei (AGN). We select clusters with , mimicking the typical selection of
Sunyaev-Zeldovich samples. This permits to have a mass range large enough to
enable robust fitting of the relations even at . The results of the
analysis show a general agreement with observations. The values of the slope of
the mass-gas mass and mass-temperature relations at are 10 per cent lower
with respect to due to the applied mass selection, in the former case,
and to the effect of early merger in the latter. We investigate the impact of
the slope variation on the study of the evolution of the normalization. We
conclude that cosmological studies through scaling relations should be limited
to the redshift range , where we find that the slope, the scatter, and
the covariance matrix of the relations are stable. The scaling between mass and
is confirmed to be the most robust relation, being almost independent of
the gas physics. At higher redshifts, the scaling relations are sensitive to
the inclusion of AGNs which influences low-mass systems. The detailed study of
these objects will be crucial to evaluate the AGN effect on the ICM.Comment: 24 pages, 11 figures, 5 tables, replaced to match accepted versio
Il diritto delle persone con disabilità al progetto individuale: importanti conferme dalla più recente giurisprudenza
A partire dalla legge 328 del 2000, il legislatore ha realizzato una serie di interventi per favorire la diffusione del cosiddetto modello progettuale, promuovendo azioni di welfare incentrate sulla creazione di un progetto ad hoc, per offrire un insieme di servizi e di risorse finalizzati alla realizzazione degli obiettivi concordati con il soggetto richiedente. In questa cornice, il giudice amministrativo \ue8 stato chiamato in numerose occasioni a definire il perimetro e il contenuto del diritto al progetto individuale, venendo a risolvere nel corso degli anni criticit\ue0 di ordine sia processuale che sostanziale. L\u2019esame della pi\uf9 recente giurisprudenza amministrativa, di cui si offre un sintetico resoconto con il seguente scritto, presenta interessanti spunti di riflessione e, per quanto pi\uf9 rileva, conferma l\u2019idea che del diritto al progetto individuale si debba parlare in termini di piena effettivit\ue0
The Relation Between Halo Shape, Velocity Dispersion and Formation Time
We use dark matter haloes identified in the MareNostrum Universe and galaxy
groups identified in the Sloan Data Release 7 galaxy catalogue, to study the
relation between halo shape and halo dynamics, parametrizing out the mass of
the systems. A strong shape-dynamics, independent of mass, correlation is
present in the simulation data, which we find it to be due to different halo
formation times. Early formation time haloes are, at the present epoch, more
spherical and have higher velocity dispersions than late forming-time haloes.
The halo shape-dynamics correlation, albeit weaker, survives the projection in
2D (ie., among projected shape and 1-D velocity dispersion). A similar
shape-dynamics correlation, independent of mass, is also found in the SDSS DR7
groups of galaxies and in order to investigate its cause we have tested and
used, as a proxy of the group formation time, a concentration parameter. We
have found, as in the case of the simulated haloes, that less concentrated
groups, corresponding to late formation times, have lower velocity dispersions
and higher elongations than groups with higher values of concentration,
corresponding to early formation times.Comment: MNRAS in press (10 pages, 10 figures
Machine learning to identify ICL and BCG in simulated galaxy clusters
Nowadays, Machine Learning techniques offer fast and efficient solutions for classification problems that would require intensive computational resources via traditional methods. We examine the use of a supervised Random Forest to classify stars in simulated galaxy clusters after subtracting the member galaxies. These dynamically different components are interpreted as the individual properties of the stars in the Brightest Cluster Galaxy (BCG) and IntraCluster Light (ICL). We employ matched stellar catalogues (built from the different dynamical properties of BCG and ICL) of 29 simulated clusters from the DIANOGA set to train and test the classifier. The input features are cluster mass, normalized particle cluster-centric distance, and rest-frame velocity. The model is found to correctly identify most of the stars, while the larger errors are exhibited at the BCG outskirts, where the differences between the physical properties of the two components are less obvious. We investigate the robustness of the classifier to numerical resolution, redshift dependence (up to z = 1), and included astrophysical models. We claim that our classifier provides consistent results in simulations for z 0.1 R-200) is significantly affected by uncertainties in the classification process. In conclusion, this work suggests the importance of employing Machine Learning to speed up a computationally expensive classification in simulations
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