We derive here the mean temperature profile for a sample of hot, medium distant clusters recently observed with XMM-Newton, whose profiles are available from the literature, and compare it with the mean temperature profile found from BeppoSAX data. The XMM-Newton and BeppoSAX profiles are in good agreement between 0.05 and 0.25 $r_{180}$. From 0.25 to about 0.5 $r_{180}$ both profiles decline; however the BeppoSAX profile does so much more rapidly than the XMM-Newton profile.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Central regions of superclusters are the ideal places where to study cluster merging phenomena: in fact the accretion activity is enhanced, as predicted by the cosmological simulations. In this paper I review the case-study of the Shapley Concentration, aimed to understand the effect of major mergings on the intracluster medium and the galaxy population of the involved clusters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present first results for spectroscopic observations of galaxies in 4 clusters at $z=0.7-0.8$ and one cluster at $z=0.5$ observed by the ESO Distant Cluster Survey (EDisCS). Our spectroscopic catalogues contain 236 cluster members of our 5 clusters, and the number of members per cluster ranges from 30 to 67. Our cluster velocity dispersions are between $\sim$400 and over 1000 $\rm{km s}^{-1}$. Galaxy redshift distributions are found to be non-Gaussian and we find evidence for significant substructure in two clusters, one at $z \sim 0.79$ and another at $z \sim 0.54$; both clusters have velocity dispersions exceeding 1000 $\rm{km~s}^{-1}$. These systems have clearly not yet virialised at these epochs in qualitative agreement with CDM scenarios and their cluster velocity dispersions should not be used in the measurement of cluster mass. Our clusters have a wide range of different cluster velocity dispersions, richnesses and substructuring, and our spectroscopic data set is allowing a comprehensive insight into cluster galaxy evolution as a function of redshift and environment.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using extensive ground-based spectroscopy, we isolate the E+A population in three intermediate redshift clusters ($z=0.33$, 0.58 and 0.83) and study their physical properties using HST/WFPC2 imaging. Our analysis includes galaxy colors, luminosities, Hubble types, and quantitative structural parameters as well as measured and estimated internal velocity dispersions. We find E+A galaxies make up a non-negligible fraction ($\sim7-13\%$) of cluster members at these redshifts, and their diverse nature indicates a heterogeneous parent population. From their velocity dispersions and half-light radii, we infer that the descendants of the E+A's in our highest redshift clusters are massive early-type galaxies, and we estimate that $\gtrsim30\%$ of the E-S0 members have undergone an E+A phase. We also find the characteristic E+A mass decreases with decreasing redshift; this is similar to the decrease in luminosity of rapidly star-forming field galaxies since $z\sim1$, i.e. galaxy “down-sizing”.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present preliminary results from a wide-field spectroscopic survey of two galaxy clusters at $z=0.4$, separated by $\lt$10 $h^{-1}$ Mpc on the sky. Both clusters are similarly optically rich, have velocity dispersions $\sim 700$ km s$^{-1}$, but differ in X-ray luminosity by a factor of $\sim$20.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from dynamical Monte Carlo simulations of dense star clusters near the Galactic center (GC). While these clusters spiral in toward the GC by dynamical friction, they could undergo core collapse and form an intermediate mass black hole (IMBH) by runaway collisions. Clusters can reach within a parsec of the GC where, following tidal disruption, they would inject many young stars still bound to the IMBH into the GC region. This scenario (Gerhard 2001; Hansen & Milosavljević 2003) provides a possible explanation for the youth paradox raised by recent IR observations (Ghez et al. 2003).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

AGN activity is known to drive fast outflows of gas. We report the discovery of fast outflows of neutral gas with velocities over 1000 km/s in a number of radio galaxies. In the best studied object, 3C 293, the kinematical properties of the neutral and ionised outflows are similar, indicating a common origin. Moreover, the outflow appears to be located near the radio lobes and not near the nucleus. This suggests that the interaction between the radio jet and the ISM is driving the outflow.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By fitting to the quiescent galaxy MBH−σ∗ relation, we calculate the average shift required to scale reverberation-mapped AGN masses to the same zero-point. We use reanalyzed virial products (rV2/G) and both new and published velocity dispersions to find the offset in the AGN calibration. This scaling factor, 〈f〉, accounts for the detailed dynamics and geometry of the broad-line region (BLR). Finally, we confirm the rough correlation between σ∗ and FWHM([O III]) for these 16 AGNs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We explore the region of influence of a galaxy cluster using numerical simulations of cold dark matter halos. Many of the observed galaxies in a cluster are expected to be infalling for the first time. Half of the halos at distances of one to two virial radii today have previously orbited through the cluster, most of them have even passed through the dense inner regions of the cluster. Some halos at distances of up to three times the virial radius have also passed through the cluster core. We do not find a significant “infall age” versus present day position for substructures and the scatter at a given position is very large. This relation may be much more significant if we could resolve the physically overmerged galaxies in the central region.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Atomic gas in the central kiloparsec of young radio galaxies is quite prevalent, as revealed by 21cm H I absorption line observations using the WSRT. The column depths are anti-correlated with the linear sizes of the radio sources, but VLBI reveals that sometimes the neutral hydrogen is situated in a disk or torus on parsec or sub-kiloparsec scales around the central engine, while in other cases the H I is probably associated with star-forming regions along the jets. NGC 1052 is a nearby example, in which, next to some isolated clouds along the jets, there appears to be an atomic and molecular torus with a radius of a few parsecs, but with a central hole of about 0.5 pc, in which the gas is mostly ionised.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

First results from the AGN-Heidelberg program aimed at spatially resolving the central pc region of the closest Active Galactic Nuclei are presented. The core region of prototype active nuclei are clearly unveiled at IR waves and at distances from the nucleus – few pc- where circumnuclear starforming regions appear not to be present. Within that perspective, classical active nuclei as Circinus and NGC 1097, reveal with unprecedented detail clear channels of material being driven to the core whereas others as Centaurus A and NGC 5506, show a “clean” core environment. At the very center, a central compact region of ∼2 pc scale is resolved in Circinus but not in the other cases challenging thus the universal presence of the putative obscuring torus.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Analysing mid–infrared ISOCAM images of the cluster of galaxies J1888.16CL, we identified among its members several particularly active galaxies with total infrared luminosities well above $10^{11}~\Lo$. If powered by dust enshrouded starbursts, as suggested by their optical spectra, these Luminous Infrared Galaxies would exhibit star formation rates surprisingly high in the cluster environment. The triggering mechanism is unclear but could be tidal collisions within sub-structures or infalling groups.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this paper we report on our recent results connected with the direct environment of the super massive black hole of the Milky Way. The data are obtained using the VLT facilities (ISAAC and NAOS/CONICA instruments) in the near- and mid-infrared wavelength ranges. We provide a calibration of the foreground and local differential (in wavelength and spatially) extinction of the Galactic Center and report on the discovery of a new complex of infrared excess sources (possibly young stars) located at the northern part of the IRS 13 cluster. Finally, we discuss the origin of filamentary structures observed in the L-band images.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

I describe very briefly the new libraries of empirical spectra of stars covering wide ranges of values of the atmospheric parameters Teff, log g, [Fe/H], as well as spectral type, that have become available in the recent past, among them the HNGSL, MILES, UVES-POP, and Indo-US libraries. I show the results of using the HNGSL to build population synthesis models. These libraries are complementary in spectral resolution and wavelength coverage, and will prove extremely useful to describe spectral features expected in galaxy spectra from the NUV to the NIR.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Popular internal shock models, developed to explain the production of high energy flares in blazar jets, involve collisions between local overdensities of matter being ejected by a central engine and moving along the jet with different velocities. Prior to such collisions, the matter is relatively cold and therefore does not produce intrinsic non-thermal radiation. However, due to Comptonization of external radiation by cold electrons, the presence of such matter should be apparent by prominent precursor soft X-ray flares. We discuss the predicted properties of such precursors.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the analysis and results of a new spectroscopic and photometric survey of the central 1.5 ${\rm Mpc}^2$ region of the galaxy cluster A3921 (z=0.094). We detect the presence of two dominant clumps of galaxies with a mass ratio of $\sim$4-5: a main cluster centered on the BCG (A3921-A), and a NW sub-cluster (A3921-B) hosting the second brightest cluster object. By comparing optical results to the X-ray analysis of XMM observations (Belsole et al. 2004), we find that A3921-B is tangentially traversing the main cluster along a SW/NE direction. The analysis of stellar populations of more than one hundred cluster members reveals that the merger event has probably affected the kinematics and spectral properties of the active galaxies in A3921.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use preliminary results of WINGS survey (Fasano et al.) to obtain determinations of optical scaling relations for galaxy clusters. Passing from one- to two- parameter scaling relations we pay particular attention to the Kormendy relation (KR) and to the Fundamental Plane (FP) of galaxy clusters, comparing them with scaling relations of elliptical galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A detailed analysis of the spectrum of I Zw 1 shows that the Narrow Line Region, unlike that of most Seyfert 1 galaxies, is a very low excitation region dominated by both permitted and forbidden Fe II lines. The physical conditions in this region are discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

From a long-term study of IR mergers/QSOs (at low redshift), we report detailed spectroscopic evidences for outflow (OF)and starburst features. We found extreme velocity OF (EVOF) in IRAS 01003-2238, 11119+3257, 13218+0552, 14394+5332, 15130-1958 and 15462-0450. The EVOF were detected mainly in objects with strong starburst plus obscured IR QSOs. Meanwhile, the low velocity OF components were detected in objects with starburst and LINER processes. HST images of IR+BAL+Fe II QSOs show in practically all of these objects “arc or shell” features probably associated to galactic-winds. In addition, results from a study of two-dimensional (2D) fibre spectroscopy of IR mergers/QSOs with galactic winds are presented. Comparing our data base for IR mergers/QSOs with two sample of nearby mergers we found in both samples a high proportion (75 per cent) of IR mergers with galactic winds.

From a very deep imaging and spectroscopic survey of Lyα emitters (LAEs) at z=5.7 we present the results of a study of sample of 20 LAEs candidates. Two of these objects have been already confirmed as LAE at z = 5.7. We detected in one of these LAE (at z=5.687), spectral features probably associated with the more distant galactic wind observed to date.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The abundance of α-process elements such as magnesium and carbon relative to iron, measured from the broad emission lines of QSOs, can serve as a diagnostic of the star formation and chemical enrichment histories of their host galaxies. We investigate the relationship between Fe/Mg and Fe/C abundance ratios and the resulting Fe II / Mg II λ2800 and Fe II / 1900Å-blend flux ratios, both of which have been measured in QSOs out to z≈6. Using a galactic chemical evolution model based on a starburst in a giant elliptical galaxy, we find that these flux ratios are good tracers of the chemical enrichment of the nuclei. However, the values of these ratios measured in objects at z≈6 suggest that iron enrichment has occurred more rapidly in these objects than predicted by the assumed elliptical starburst model, assuming currently favored cosmologies. This in turn suggests that refinements to the galactic chemical evolution models are needed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html