We revisit the scaling relationships between the dark matter mass and observed X– ray luminosity and temperature of galaxy clusters and groups in the local Universe. Specifically, we compare recent observations with analytic models of the intracluster medium in which the gas entropy distribution has been shifted by a variable amount, K◦, to investigate the origin of the scatter in these scaling...

One hundred and five 15μm selected objects in three ISO (Infrared Space Observatory) deep survey fields (CFRS 3, UDSR and UDSF) are studied on the basis of their high quality optical spectra with resolution R>1000 from VLT/FORS2. Ninety two objects (88%) have secure redshifts, ranging from 0 to 1.16 with a median value of zmed=0.587. Considerable care is taken in estimating the extinction prope...

We present a comparison of the predictions of stellar models with the luminosity of the lower main sequence (5.5 < MV < 7.3) using K dwarfs in the Hipparcos catalog. The parallaxes of our comparison stars are known to better than 15% and metallicities have been recently determined from photometry. A major advantage of our comparison is that distances in our sample are known with good accuracy, ...

Using a simple description of feedback from black hole growth, we develop an analytic model for the fueling of Seyferts (low-luminosity AGN) and their relation to their host galaxies, Eddington ratio distributions, and cosmological evolution. We derive a solution for the time evolution of accretion rates in a feedback-driven blast wave, applicable to large-scale outflows from bright quasars in ...

We have observed three fields of the Coma cluster of galaxies with a narrow band (modified Strömgren) filter system. Observed galaxies include 31 in the vicinity of NGC 4889, 48 near NGC 4874, and 60 near NGC 4839 complete to M5500 = −18 in all three subclusters. Spectrophotometric classification finds all three subclusters of Coma to be dominated by red, E type (ellipticals/S0’s) galaxies with...

Context. It has been shown that the luminosity of active galactic nuclei and the size of their broad line region obey a simple relation of the type RBLR = aL, from faint Seyfert nuclei to bright quasars, allowing single-epoch determination of the central black hole mass MBH = bL∆Hβ from their luminosity L and width of Hβ emission line. Adopting this mass determination for cosmological studies r...

We outline a framework for understanding the X-ray spectra of high mass accretion rate stellar black holes based on X-ray data from RXTE and ASCA. Three spectral regimes can be separated out by the behaviour of the observed disk luminosity and temperature. The well established ”standard regime” is seen when the disk dominates the spectrum, where only a small fraction of the luminosity is emitte...

The size-luminosity relation of early-type Brightest Cluster Galaxies (BCGs), Re ∝ L , is steeper than that for the bulk of the early-type galaxy population, for which Re ∝ L . This is true if quantities derived from either deVaucouleur or Sersic fits to the surface brightness profiles are used. Contamination from an intra-cluster light component centered on the BCG, with similar parameters to ...