arXiv subjects

L. Lovisari

Publications and source records attributed to L. Lovisari.

63 records · Page 4Linked to original sources

arXiv2014

A metal-rich elongated structure in the core of the group NGC4325

We used X-ray 2D spectrally resolved maps to resolve structure in temperature and metal abundance. To perform stellar population analysis we applied the spectral fitting technique with STARLIGHT to the optical spectrum of the central galaxy. We simulated the chemical evolution of the central galaxy. While the temperature, pseudo-pressure, and pseudo-entropy maps showed no inhomogeneities, the iron spatial distribution shows a filamentary structure in the core of this group, which is spatially correlated with the central galaxy, suggesting a connection between the two. The analysis of the optical spectrum of the central galaxy showed no contribution by any recent AGN activity. Using the star formation history as input to chemical evolution models, we predicted the iron and oxygen mass released by supernovae (SNe) winds in the central galaxy up to the present time. Comparing the predicted amount of mass released by the NGC4325 galaxy to the ones derived through X-ray analysis we conclude that the winds from the central galaxy alone play a minor role in the IGM metal enrichment of this group inside r2500. The SNe winds are responsible for no more than 3% of it and of the iron mass and 21% of the oxygen mass enclosed within r2500. Our results suggest that oxygen has been produced in the early stages of the group formation, becoming well mixed and leading to an almost flat profile. Instead, the iron distribution is centrally peaked, indicating that this element is still being added to the IGM specifically in the core by the SNIa. A possible scenario to explain the elongated iron-rich structure in the core of the NGC4325 is a past AGN activity, in which our results suggest an episode older than ~10^7-10^8 yrs and younger than 5x10^8.

astro-ph.GA↗

arXiv2014

Extending the $L_{\mathrm{X}}-T$ relation from clusters to groups-Impact of cool core nature, AGN feedback, and selection effects

We aim to investigate the bolometric $L_{\mathrm{X}}-T$ relation for galaxy groups, and study the impact of gas cooling, feedback from supermassive black holes, and selection effects on it. With a sample of 26 galaxy groups we obtained the best fit $L_{\mathrm{X}}-T$ relation for five different cases depending on the ICM core properties and central AGN radio emission, and determined the slopes, normalisations, intrinsic and statistical scatters for both temperature and luminosity. Simulations were undertaken to correct for selection effects (e.g. Malmquist bias) and the bias corrected relations for groups and clusters were compared. The slope of the bias corrected $L_{\mathrm{X}}-T$ relation is marginally steeper but consistent with clusters ($\sim 3$). Groups with a central cooling time less than 1 Gyr (SCC groups) show indications of having the steepest slope and the highest normalisation. For the groups, the bias corrected intrinsic scatter in $L_{\mathrm{X}}$ is larger than the observed scatter for most cases, which is reported here for the first time. Lastly, we see indications that the groups with an extended central radio source have a much steeper slope than those groups which have a CRS with only core emission. Additionally, we also see indications that the more powerful radio AGN are preferentially located in NSCC groups rather than SCC groups.

astro-ph.CO↗

arXiv2013

The Hot and Energetic Universe: The evolution of galaxy groups and clusters

Major astrophysical questions related to the formation and evolution of structures, and more specifically of galaxy groups and clusters, will still be open in the coming decade and beyond: what is the interplay of galaxy, supermassive black hole, and intergalactic gas evolution in the most massive objects in the Universe - galaxy groups and clusters? What are the processes driving the evolution of chemical enrichment of the hot diffuse gas in large-scale structures? How and when did the first galaxy groups in the Universe, massive enough to bind more than 10^7 K gas, form? Focussing on the period when groups and clusters assembled (0.5<z<2.5), we show that, due to the continuum and line emission of this hot intergalactic gas at X-ray wavelengths, Athena+, combining high sensitivity with excellent spectral and spatial resolution, will deliver breakthrough observations in view of the aforementioned issues. Indeed, the physical and chemical properties of the hot intra-cluster gas, and their evolution across time, are a key to understand the co-evolution of galaxy and supermassive black hole within their environments.

astro-ph.HE↗

arXiv2013

Scaling relations for galaxy clusters: properties and evolution

Well-calibrated scaling relations between the observable properties and the total masses of clusters of galaxies are important for understanding the physical processes that give rise to these relations. They are also a critical ingredient for studies that aim to constrain cosmological parameters using galaxy clusters. For this reason much effort has been spent during the last decade to better understand and interpret relations of the properties of the intra-cluster medium. Improved X-ray data have expanded the mass range down to galaxy groups, whereas SZ surveys have openened a new observational window on the intracluster medium. In addition,continued progress in the performance of cosmological simulations has allowed a better understanding of the physical processes and selection effects affecting the observed scaling relations. Here we review the recent literature on various scaling relations, focussing on the latest observational measurements and the progress in our understanding of the deviations from self similarity.

astro-ph.CO↗

arXiv2013

Mass profiles of Galaxy Clusters from X-ray analysis

We review the methods adopted to reconstruct the mass profiles in X-ray luminous galaxy clusters. We discuss the limitations and the biases affecting these measurements and how these mass profiles can be used as cosmological proxies.

astro-ph.CO↗

arXiv2011

Gas sloshing, cold fronts, Kelvin-Helmholtz instabilities and the merger history of the cluster of galaxies Abell 496

We investigate the origin and nature of the multiple sloshing cold fronts in the core of Abell 496 by direct comparison between observations and dedicated hydrodynamical simulations. Our simulations model a minor merger with a 4{\times}10^13M{\circ} subcluster crossing A496 from the south-west to the north-north-east, passing the cluster core in the south-east at a pericentre distance 100 to a few 100 kpc about 0.6 to 0.8 Gyr ago. The gas sloshing triggered by the merger can reproduce almost all observed features, e.g. the characteristic spiral-like brightness residual distribution in the cluster centre and its asymmetry out to 500 kpc, also the positions of and contrasts across the cold fronts. If the subcluster passes close (100 kpc) to the cluster core, the resulting shear flows are strong enough to trigger Kelvin-Helmholtz instabilities that in projection resemble the peculiar kinks in the cold fronts of Abell 496. Finally, we show that sloshing does not lead to a significant modification of the global ICM profiles but a mild oscillation around the initial profiles.

astro-ph.CO↗

arXiv2011

Inhomogeneous Metal Distribution in the Intra-Cluster Medium

The hot gas that fills the space between galaxies in clusters is rich in metals. In their large potential wells, galaxy clusters accumulate metals over the whole cluster history and hence they retain important information on cluster formation and evolution. We use a sample of 5 cool core clusters to study the distribution of metals in the ICM. We investigate whether the X-ray observations yield good estimates for the metal mass and whether the heavy elements abundances are consistent with a certain relative fraction of SN Ia to SNCC. We derive detailed metallicity maps of the clusters from XMM - Newton observations and we use them as a measure for the metal mass in the ICM. We determine radial profiles for several elements and using population synthesis and chemical enrichment models, we study the agreement between the measured abundances and the theoretical yields. We show that even in relaxed clusters the distribution of metals show a lot of inhomogeneities. Using metal maps usually gives a metal mass 10-30% higher than the metal mass computed using a single extraction region, hence it is expected that most previous metal mass determination have underestimated metal mass. The abundance ratio of α-elements to Fe, even in the central parts of clusters, are consistent with an enrichment due to the combination of SN Ia and SNCC.

astro-ph.CO↗

arXiv2009

Metallicity map of the galaxy cluster A3667

We use XMM-Newton data of the merging cluster Abell 3667 to analyze its metallicity distribution. A detailed abundance map of the central 1.1x1.1 Mpc region indicates that metals are inhomogeneously distributed in the cluster showing a non-uniform and very complex metal pattern. The highest peak in the map corresponds to a cold region, slightly offset South of the X-ray center. This could be interpreted as stripped gas due to a merger between a group moving from NW towards the SE and the main cluster. We note several clumps of high metallicity also in the opposite direction with respect to the X-ray peak. Furthermore we determined abundances for 5 elements (O, Si, S, Ar, Fe) in four different regions of the cluster. Comparisons between these observed abundances and theoretical supernovae yields allow to get constraints on the relative number of SN Ia and II contributing to the enrichment of the intra-cluster medium. To reproduce the observed abundances of the best determined elements (Fe, O and Si) in a region of 7 arcmin around the X-ray center, 65-80% of SN II are needed. The comparison between the metal map, a galaxy density map obtained using 550 spectroscopically confirmed cluster members and our simulations suggest a recent merger between the main cluster and the group in the SE.

astro-ph.CO↗

arXiv2009

The cluster gas mass fraction as a cosmological probe: a revised study

(Abriged) We present the analysis of the baryonic content of 52 X-ray luminous galaxy clusters observed with Chandra in the redshift range 0.3-1.273. We use the deprojected X-ray surface brightness profiles and the measured values of the gas temperature to recover the gas and total mass profiles. By assuming that galaxy clusters are representative of the cosmic baryon budget, the distribution of the cluster baryon fraction in the hottest (T> 4 keV) systems as a function of redshift is used to constrain the cosmological parameters. We discuss how our constraints are affected by several systematics, namely the isothermality, the assumed baryon fraction in stars, the depletion parameter and the sample selection. By using only the cluster baryon fraction as a proxy for the cosmological parameters, we obtain that Omega is very well constrained at the value of 0.35 with a relative statistical uncertainty of 11% (1 sigma level; w=-1) and a further systematic error of about (-6,+7)%. On the other hand, constraints on Lambda (without the prior of flat geometry) and w (using the prior of flat geometry) are definitely weaker due to the presence of larger statistical and systematic uncertainties (of the order of 40 per cent on Lambda and larger than 50 per cent on w). If the WMAP 5-year best-fit results are assumed to fix the cosmological parameters, we limit the contributions expected from non-thermal pressure support and ICM clumpiness to be lower than about 10 per cent, leaving also room to accommodate baryons not accounted for either in the X-ray emitting plasma or in stars of the order of 18 per cent of the total cluster baryon budget.

astro-ph.CO↗