arXiv subjects

A. Finoguenov

Publications and source records attributed to A. Finoguenov.

At least 199 records · Page 11Linked to original sources

arXiv2008

Metal-rich multi-phase gas in M87: AGN-driven metal transport, magnetic-field supported multi-temperature gas, and constraints on non-thermal emission observed with XMM-Newton

We use deep (~120 ks) XMM-Newton data of the M87 halo to analyze its spatially resolved temperature structure and chemical composition. We focus particularly on the regions of enhanced X-ray brightness associated with the inner radio lobes, which are known not to be described very well by single-temperature spectral models. Compared to a simple two-temperature fit, we obtain a better and more physical description of the spectra using a model that involves a continuous range of temperatures in each spatial bin. The range of temperatures of the multiphase gas spans ~0.6-3.2 keV. Such a multiphase structure is only possible if thermal conduction is suppressed by magnetic fields. In the multi-temperature regions, we find a correlation between the amount of gas cooler than the surrounding X-ray plasma and the metallicity, and conclude that the cool gas is more metal-rich than the ambient halo. We estimate the average Fe abundance of the cool gas to ~2.2 solar. Our results thus point toward the key role of the active galactic nucleus (AGN) in transporting heavy elements into the intracluster medium. The abundance ratios of O/Si/S/Fe in and outside the X-ray arms are similar, indicating that the dominant fraction of metals in the gas halo was uplifted by AGN outbursts relatively recently compared to the age of M87. Our estimate for the mass of the cool gas is 5e8 M_sun, which probably stems from a mixture of ICM, stellar mass loss, and Type Ia supernova products. ~30-110 Myr are required to produce the observed metals in the cool gas. Finally, we put upper limits on possible non-thermal X-ray emission from M87 and, combining it with the 90 cm radio maps, we put lower limits of around ~0.5-1.0 muG on the magnetic field strength.

astro-ph↗

arXiv2007

Complex X-ray morphology of Abell 3128: A distant cluster behind a disturbed cluster

We present here the results of a detailed study of the X-ray properties of the cluster of galaxies Abell 3128 (z=0.06), based on the analysis of deep (100 ks) XMM-Newton data. The most obvious feature of the X-ray morphology of A3128 is the presence of two X-ray peaks separated by ~12'. By detecting the redshifted Fe K line, we find that the Northeast (NE) X-ray peak observed toward A3128 is a distant luminous cluster of galaxies at redshift z=0.44. Our subsequent optical spectroscopic observation of a distant radio bright galaxy in the centre of the NE X-ray peak with the Magellan telescope also revealed a redshift of z=0.44, confirming the association of the galaxy with the cluster seen in X-rays. We detect a gravitational arc around the galaxy. The properties of this galaxy indicate that it is the cD galaxy of the cluster in the background. The properties of the Southwest X-ray peak suggest that it is the core of a group merging with A3128 along our line of sight. Based on 2D maps of thermodynamic properties of the intra-cluster medium determined after subtracting a model for the background cluster, we conclude that an enhanced surface brightness region at a distance of ~2.8' from the centre of the galaxy distribution is the centre of the gravitational potential of the cluster A3128. The unrelaxed nature of A3128 can be attributed to its location in the high density environment of the Horologium-Reticulum supercluster.

astro-ph↗

arXiv2007

The angular correlations of galaxies in the COSMOS field

We present measurements of the two-point galaxy angular correlation function w(θ) in the COSMOS field. Independent determinations of w(θ) as a function of magnitude limit are presented for both the HST ACS catalog and also for the ground-based data from Subaru and the CFHT. Despite having significantly different masks, these three determinations agree well. At bright magnitudes (IAB<22), our data generally match very well with existing measurements and with mock catalogs based on semi-analytic galaxy formation calculations of Kitzbichler and White from the Millennium Simulation. The exception is that our result is at the upper end of the expected cosmic variance scatter for θ> 10 arcmin, which we attribute to a particularly rich structure known to exist at z~0.8. For fainter samples, however, the level of clustering is somewhat higher than reported by some previous studies: in all three catalogues we find w(θ=1')~0.014 at a median IAB magnitude of 24. At these very faintest magnitudes, our measurements agree well with the latest determinations from the Canada-France Legacy Survey. This level of clustering is approximately double what is predicted by the semi-analytic catalogs (at all angles). The semi-analytic results allow an estimate of cosmic variance, which is too small to account for the discrepancy. We therefore conclude that the mean amplitude of clustering at this level is higher than previously estimated.

astro-ph↗

arXiv2007

X-ray source counts in the COSMOS field

We present the analysis of the source counts in the XMM-COSMOS survey using data of the first year of XMM-Newton observations. The survey covers ~2 deg^2 within the region of sky bounded by 9^h57.5^m<R.A.<10^h03.5^m; 1^d27.5^m<DEC<2^d57.5^m with a total net integration time of 504 ks. Using a maximum likelihood algorithm we detected a total of 1390 sources at least in one band. Using Monte Carlo simulations to estimate the sky coverage we produced the logN-logS relations. These relations have been then derived in the 0.5--2 keV, 2--10 keV and 5--10 keV energy bands, down to flux limits of 7.2x10^-16 erg cm^-2 s^-1, 4.0x10^-15 erg cm^-2 s^-1 and 9.7x10^-15 erg cm^-2 s^-1, respectively. These relations have been compared to previous X-ray survey and to the most recent X-ray background model finding an excellent agreement. The slightly different normalizations observed in the source counts of COSMOS and previous surveys can be largely explained as a combination of low counting statistics and cosmic variance introduced by the large scale structure.

astro-ph↗

arXiv2007

Scaling relations and mass calibration of the X-ray luminous galaxy clusters at z~0.2: XMM-Newton observations

We present the X-ray properties and scaling relations of a flux-limited morphology-unbiased sample of 12 X-ray luminous galaxy clusters at redshift around 0.2 based on XMM-Newton observations. The scaled radial profiles are characterized by a self-similar behavior at radii outside the cluster cores (>0.2 r500) for the temperature, surface brightness, entropy, gas mass and total mass. The cluster cores contribute up to 70% of the bolometric X-ray luminosity. The X-ray scaling relations and their scatter are sensitive to the presence of the cool cores. Using the X-ray luminosity corrected for the cluster central region and the temperature measured excluding the cluster central region, the normalization agrees to better than 10% for the cool core clusters and non-cool core clusters, irrelevant to the cluster morphology. No evolution of the X-ray scaling relations was observed comparing this sample to the nearby and more distant samples. With the current observations, the cluster temperature and luminosity can be used as reliable mass indicators with the mass scatter within 20%. Mass discrepancies remain between X-ray and lensing and lead to larger scatter in the scaling relations using the lensing masses (e.g. ~40% for the luminosity--mass relation) than using the X-ray masses (<20%) due to the possible reasons discussed.

astro-ph↗

arXiv2007

The Representative XMM-Newton Cluster Structure Survey (REXCESS) of an X-ray Luminosity Selected Galaxy Cluster Sample

The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge of the statistics of galaxy cluster structure, and of the scaling relations between observables and cluster mass. To improve on this situation we have started an XMM-Newton Large Programme for the in-depth study of a representative sample of 33 galaxy clusters, selected in the redshift range z=0.055 to 0.183 from the REFLEX Cluster Survey, having X-ray luminosities above 0.4 X 10^44 h_70^-2 erg s^-1 in the 0.1 - 2.4 keV band. This paper introduces the sample, compiles properties of the clusters, and provides detailed information on the sample selection function. We describe the selection of a nearby galaxy cluster sample that makes optimal use of the XMM-Newton field-of-view, and provides nearly homogeneous X-ray luminosity coverage for the full range from poor clusters to the most massive objects in the Universe. For the clusters in the sample, X-ray fluxes are derived and compared to the previously obtained fluxes from the ROSAT All-Sky Survey. We find that the fluxes and the flux errors have been reliably determined in the ROSAT All-Sky Survey analysis used for the REFLEX Survey. We use the sample selection function documented in detail in this paper to determine the X-ray luminosity function, and compare it with the luminosity function of the entire REFLEX sample. We also discuss morphological peculiarities of some of the sample members. The sample and some of the background data given in this introductory paper will be important for the application of these data in the detailed studies of cluster structure, to appear in forthcoming publications.

astro-ph↗

arXiv2007

Large Structures and Galaxy Evolution in COSMOS at z < 1.1

We present the first identification of large-scale structures (LSS) at z $< 1.1$ in the Cosmic Evolution Survey (COSMOS). The structures are identified from adaptive smoothing of galaxy counts in the pseudo-3d space ($α,δ$,z) using the COSMOS photometric redshift catalog. The technique is tested on a simulation including galaxies distributed in model clusters and a field galaxy population -- recovering structures on all scales from 1 to 20\arcmin without {\it a priori} assumptions for the structure size or density profile. Our procedure makes {\bf no} {\it a priori} selection on galaxy spectral energy distribution (SED, for example the Red Sequence), enabling an unbiased investigation of environmental effects on galaxy evolution. The COSMOS photometric redshift catalog yields a sample of $1.5\times10^5$ galaxies with redshift accuracy, $Δz_{FWHM}/(1+z) \leq 0.1$ at z $< 1.1$ down to I$_{AB} \leq 25$ mag. Using this sample of galaxies, we identify 42 large-scale structures and clusters. abstract truncated for astroph 25 line limit -- see preprint

astro-ph↗

arXiv2007

The gaseous atmosphere of M87 seen with XMM-Newton

M87 is a key object whose study can reveal the complex phenomena in cooling cores. We use a deep XMM-Newton observation of M87 to produce detailed temperature, pressure and entropy maps in order to analyze the physical processes of cooling cores and of their heating mechanisms. We employed both broad-band fitting and full spectroscopical one-temperature model analysis to derive temperature and surface brightness maps, from which the pseudo-deprojected entropy and pressure were calculated. We discuss possible physical interpretations of small deviations from radial and elliptical symmetry in these maps. The most prominent features observed are the E and SW X-ray arms that coincide with powerful radio lobes, a weak shock at a radius of 3', an overall ellipticity in the pressure map and a NW/SE asymmetry in the entropy map which we associate with the motion of the galaxy towards the NW. For the first time we find evidence that cold, metal-rich gas is being transported out of the center, possibly through bubble-induced mixing. Several edges in the abundance map indicate an oscillation of the galaxy along the NW/SE direction. Furthermore, the radio lobes appear to rise along the short axis of the elliptical pressure distribution, following the steepest gradient of the gravitational potential, and seem to contain a nonthermal pressure component.

astro-ph↗

arXiv2007

The Cosmic Evolution Survey (COSMOS): a large-scale structure at z=0.73 and the relation of galaxy morphologies to local environment

We have identified a large-scale structure at z~0.73 in the COSMOS field, coherently described by the distribution of galaxy photometric redshifts, an ACS weak-lensing convergence map and the distribution of extended X-ray sources in a mosaic of XMM observations. The main peak seen in these maps corresponds to a rich cluster with Tx= 3.51+0.60/-0.46 keV and Lx=(1.56+/-0.04) x 10^{44} erg/s ([0.1-2.4] keV band). We estimate an X-ray mass within $r500$ corresponding to M500~1.6 x 10^{14} Msun and a total lensing mass (extrapolated by fitting a NFW profile) M(NFW)=(6+/-3) x 10^15 Msun. We use an automated morphological classification of all galaxies brighter than I_AB=24 over the structure area to measure the fraction of early-type objects as a function of local projected density Sigma_10, based on photometric redshifts derived from ground-based deep multi-band photometry. We recover a robust morphology-density relation at this redshift, indicating, for comparable local densities, a smaller fraction of early-type galaxies than today. Interestingly, this difference is less strong at the highest densities and becomes more severe in intermediate environments. We also find, however, local "inversions'' of the observed global relation, possibly driven by the large-scale environment. In particular, we find direct correspondence of a large concentration of disk galaxies to (the colder side of) a possible shock region detected in the X-ray temperature map and surface brightness distribution of the dominant cluster. We interpret this as potential evidence of shock-induced star formation in existing galaxy disks, during the ongoing merger between two sub-clusters.

astro-ph↗

arXiv2007

The XMM-Newton wide-field survey in the COSMOS field II: X-ray data and the logN-logS

We present the data analysis and the X-ray source counts for the first season of XMM-Newton observations in the COSMOS field. The survey covers ~2 deg^2 within the region of sky bounded by 9^h57.5^m<R.A.<10^h03.5^m; 1^d27.5^m<DEC<2^d57.5^m with a total net integration time of 504 ks. A maximum likelihood source detection was performed in the 0.5-2 keV, 2-4.5 keV and 4.5-10 keV energy bands and 1390 point-like sources were detected in at least one band. Detailed Monte Carlo simulations were performed to fully test the source detection method and to derive the sky coverage to be used in the computation of the logN-logS relations. The 0.5--2 keV and 2--10 keV differential logN-logS were fitted with a broken power-law model which revealed a Euclidean slope (alpha~2.5) at the bright end and a flatter slope (alpha~1.5) at faint fluxes. In the 5--10 keV energy band a single power-law provides an acceptable fit to the observed source counts with a slope alpha~2.4. A comparison with the results of previous surveys shows good agreement in all the energy bands under investigation in the overlapping flux range. We also notice a remarkable agreement between our logN-logS relations and the most recent model of the XRB. The slightly different normalizations observed in the source counts of COSMOS and previous surveys can be largely explained as a combination of low counting statistics and cosmic variance introduced by the large scale structure.

astro-ph↗

arXiv2006

The XMM-Newton wide-field survey in the COSMOS field. IV: X-ray spectral properties of Active Galactic Nuclei

We present a detailed spectral analysis of point-like X-ray sources in the XMM-COSMOS field. Our sample of 135 sources only includes those that have more than 100 net counts in the 0.3-10 keV energy band and have been identified through optical spectroscopy. The majority of the sources are well described by a simple power-law model with either no absorption (76%) or a significant intrinsic, absorbing column (20%).As expected, the distribution of intrinsic absorbing column densities is markedly different between AGN with or without broad optical emission lines. We find within our sample four Type-2 QSOs candidates (L_X > 10^44 erg/s, N_H > 10^22 cm^-2), with a spectral energy distribution well reproduced by a composite Seyfert-2 spectrum, that demonstrates the strength of the wide field XMM/COSMOS survey to detect these rare and underrepresented sources.

astro-ph↗

arXiv2006

The XMM-Newton wide-field survey in the COSMOS field: III. optical identification and multiwavelength properties of a large sample of X-ray selected sources

[ABRIGED] We present the optical identification of a sample of 695 X-ray sources detected in the first 1.3 deg^2 of the XMM-COSMOS survey, down to a 0.5-2 keV (2-10 keV) limiting flux of ~10^-15 erg cm-2 s-1 (~5x10^-15 erg cm^-2 s-1). We were able to associate a candidate optical counterpart to ~90% (626) of the X-ray sources, while for the remaining ~10% of the sources we were not able to provide a unique optical association due to the faintness of the possible optical counterparts (I_AB>25) or to the presence of multiple optical sources within the XMM-Newton error circles. We also cross-correlated the candidate optical counterparts with the Subaru multicolor and ACS catalogs and with the Magellan/IMACS, zCOSMOS and literature spectroscopic data; the spectroscopic sample comprises 248 objects (~40% of the full sample). Our analysis reveals that for ~80% of the counterparts there is a very good agreement between the spectroscopic classification, the morphological parameters as derived from ACS data, and the optical to near infrared colors. About 20% of the sources show an apparent mismatch between the morphological and spectroscopic classifications. All the ``extended'' BL AGN lie at redshift <1.5, while the redshift distribution of the full BL AGN population peaks at z~1.5. Our analysis also suggests that the Type 2/Type 1 ratio decreases towards high luminosities, in qualitative agreement with the results from X-ray spectral analysis and the most recent modeling of the X-ray luminosity function evolution.

astro-ph↗

arXiv2006

The XMM-Newton wide-field survey in the COSMOS field: VI. Statistical properties of clusters of galaxies

We present the results of a search for galaxy clusters in the first 36 XMM-Newton pointings on the COSMOS field. We reach a depth for a total cluster flux in the 0.5-2 keV band of 3x10-15 ergs cm-2 s-1, having one of the widest XMM-Newton contiguous raster surveys, covering an area of 2.1 square degrees. Cluster candidates are identified through a wavelet detection of extended X-ray emission. Verification of the cluster candidates is done based on a galaxy concentration analysis in redshift slices of thickness of 0.1-0.2 in redshift, using the multi-band photometric catalog of the COSMOS field and restricting the search to z<1.3 and i_AB < 25. We identify 72 clusters and derive their properties based on the X-ray cluster scaling relations. A statistical description of the survey in terms of the cumulative log(N>S)-lg(S) distribution compares well with previous results, although yielding a somewhat higher number of clusters at similar fluxes. The X-ray luminosity function of COSMOS clusters matches well the results of nearby surveys, providing a comparably tight constraint on the faint end slope of alpha=1.93+/-0.04. For the probed luminosity range of 8x10+42 - 2x10+44 ergs s-1, our survey is in agreement with and adds significantly to the existing data on the cluster luminosity function at high redshifts and implies no substantial evolution at these luminosities to z=1.3.

astro-ph↗

arXiv2006

The XMM-Newton wide-field survey in the COSMOS field: I. Survey description

We present the first set of XMM-Newton EPIC observations in the 2 square degree COSMOS field. The strength of the COSMOS project is the unprecedented combination of a large solid angle and sensitivity over the whole multiwavelength spectrum. The XMM-Newton observations are very efficient in localizing and identifying active galactic nuclei (AGN) and clusters as well as groups of galaxies. One of the primary goals of the XMM-Newton Cosmos survey is to study the co-evolution of active galactic nuclei as a function of their environment in the Cosmic web. Here we present the log of observations, images and a summary of first research highlights for the first pass of 25 XMM-Newton pointings across the field. In the existing dataset we have detected 1416 new X-ray sources in the 0.5-2, 2-4.5 and 4.5-10 keV bands to an equivalent 0.5-2 keV flux limit of 7x10-16 erg cm-2 s-1. The number of sources is expected to grow to almost 2000 in the final coverage of the survey. From an X-ray color color analysis we identify a population of heavily obscured, partially leaky or reflecting absorbers, most of which are likely to be nearby, Compton-thick AGN.

astro-ph↗

arXiv2006

XMM-Newton study of 0.012<z<0.024 groups. I: Overview of the IGM thermodynamics

We study the thermodynamic properties of the hot gas in a sample of groups in the 0.012-0.024 redshift range, using XMM-Newton observations. We present measurements of temperature, entropy, pressure and iron abundance. Non-parametric fits are used to derive the mean properties of the sample and to study dispersion in the values of entropy and pressure. The scaling of the entropy at 0.2r500 matches well the results of Ponman et al. (2003). However, compared to cool clusters, the groups in our sample reveal larger entropy at inner radii and a substantially flatter slope in the entropy in the outskirts, compared to both the prediction of pure gravitational heating and to observations of clusters. This difference corresponds to the systematically flatter group surface brightness profiles, reported previously. The scaled pressure profiles can be well approximated with a Sersic model with n=4. We find that groups exhibit a systematically larger dispersion in pressure, compared to clusters of galaxies, while the dispersion in entropy is similar.

astro-ph↗

arXiv2006

A wide angle tail radio galaxy in the COSMOS field: evidence for cluster formation

We have identified a complex galaxy cluster system in the COSMOS field via a wide angle tail (WAT) radio galaxy consistent with the idea that WAT galaxies can be used as tracers of clusters. The WAT galaxy, CWAT-01, is coincident with an elliptical galaxy resolved in the HST-ACS image. Using the COSMOS multiwavelength data set, we derive the radio properties of CWAT-01 and use the optical and X-ray data to investigate its host environment. The cluster hosting CWAT-01 is part of a larger assembly consisting of a minimum of four X-ray luminous clusters within ~2 Mpc distance. We apply hydrodynamical models that combine ram pressure and buoyancy forces on CWAT-01. These models explain the shape of the radio jets only if the galaxy's velocity relative to the intra-cluster medium (ICM) is in the range of about 300-550 km/s which is higher than expected for brightest cluster galaxies (BCGs) in relaxed systems. This indicates that the CWAT-01 host cluster is not relaxed, but is possibly dynamically young. We argue that such a velocity could have been induced through subcluster merger within the CWAT-01 parent cluster and/or cluster-cluster interactions. Our results strongly indicate that we are witnessing the formation of a large cluster from an assembly of multiple clusters, consistent with the hierarchical scenario of structure formation. We estimate the total mass of the final cluster to be approximately 20% of the mass of the Coma cluster.

astro-ph↗

arXiv2006

A cluster in a crowded environment: XMM-Newton and Chandra observations of A3558

Combining XMM-Newton and Chandra data, we have performed a detailed study of Abell 3558. Our analysis shows that its dynamical history is more complicated than previously thought. We have found some traits typical of cool core clusters (surface brightness peaked at the center, peaked metal abundance profile) and others that are more common in merging clusters, like deviations from spherical symmetry in the thermodynamic quantities of the ICM. This last result has been achieved with a new technique for deriving temperature maps from images. We have also detected a cold front and, with the combined use of XMM-Newton and Chandra, we have characterized its properties, such as the speed and the metal abundance profile across the edge. This cold front is probably due to the sloshing of the core, induced by the perturbation of the gravitational potential associated with a past merger. The hydrodynamic processes related to this perturbation have presumably produced a tail of lower entropy, higher pressure and metal rich ICM, which extends behind the cold front for about 500 kpc. The unique characteristics of A3558 are probably due to the very peculiar environment in which it is located: the core of the Shapley supercluster.

astro-ph↗

arXiv2006

Temperature profiles of a representative sample of nearby X-ray galaxy clusters

A study of the structural and scaling properties of the temperature distribution of the hot, X-ray emitting intra-cluster medium of galaxy clusters, and its dependence on dynamical state, can give insights into the physical processes governing the formation and evolution of structure. We analyse the X-ray temperature profiles from XMM-Newton observations of 15 nearby (z < 0.2) clusters, drawn from a statistically representative sample. The clusters cover a temperature range from 2.5 keV to 8.5 keV, and present a variety of X-ray morphologies. We derive accurate projected temperature profiles to ~ 0.5 R_200, and compare structural properties (outer slope, presence of cooling core) with a quantitative measure of the X-ray morphology as expressed by power ratios. We also compare the results to recent cosmological numerical simulations. Once the temperature profiles are scaled by an average cluster temperature (excluding the central region) and the estimated virial radius, the profiles generally decline in the region 0.1 R_200 < R < 0.5 R_200. The central regions show the largest scatter, attributable mostly to the presence of cool core clusters. There is good agreement with numerical simulations outside the core regions. We find no obvious correlations between power ratio and outer profile slope. There may however be a weak trend with the existence of a cool core, in the sense that clusters with a central temperature decrement appear to be slightly more regular. The present results lend further evidence to indicate that clusters are a regular population, at least outside the core region.

astro-ph↗