The X-ray properties of 15 nearby (v < 3, 000 km s−1) galaxies that possess AGN and/or starbursts are discussed. Two-thirds have nuclear extended emission on scales from ∼ 0.5 to ∼ 1.5 kpc that is either clearly associated with a nuclear outflow or morphologically resembles an outflow. Galaxies that are AGN-dominated tend to have linear structures while starburst-dominated galaxies tend to have...

Black holes generate collimated, relativistic jets, which have been observed in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies [active galactic nuclei (AGN)]. How jet physics scales from stellar black holes in GRBs to the supermassive ones in AGN is still unknown. Here, we show that jets produced by AGN and GRBs exhibit the same correlation between the kinetic power c...

Eddington outflows probably regulate the growth of supermassive black holes (SMBHs) in active galactic nucleus (AGN). I show that effect of the Rayleigh–Taylor instability on these outflows means that SMBH masses are likely to be a factor of a few below the M–σ relation in AGN. This agrees with the suggestion by Batcheldor that the M–σ relation defines an upper limit to the black hole mass. I f...

Optically–faint X-ray sources (those with fX/fR> 10) constitute about 20% of X-ray sources in deep surveys, and are potentially highly obscured and/or at high redshift. Their faint optical fluxes are generally beyond the reach of spectroscopy. For a sample of 20 optically–faint sources in CDFS, we compile 0.4–24 μm photometry, relying heavily on Spitzer. We estimate photometric redshifts for 17...

We analysed the optical and infrared properties of X-ray sources in the Great Observatories Origins Deep Survey (GOODS), a deep, multiwavelength survey covering 0.1 square degrees in two fields. The HST ACS data are well explained by a unified AGN scheme that postulates roughly 3 times as many obscured as unobscured AGN, as are the spectroscopic and photometric redshift distributions once selec...

Present AGN and starburst models aiming to account for the observed infrared SEDs consider a physical description of the dust and a solution of the radiative transfer problem. Mid infrared spectra obtained at different spatial scales (SST-IRS, ISO and Timmi2) are presented. They show that PAH bands are detected in starburst regions but significantly reduced near the centre of AGN. This is expla...

We examine the relationship between galaxies, supermassive black holes and AGN using a sample of 23,000 narrow-emission-line ('type 2') active galactic nuclei (AGN) drawn from a sample of 123,000 galaxies from the Sloan Digital Sky Survey. We have studied how AGN host properties compare with those of normal galaxies and how they depend on the luminosity of the active nucleus. We find that AGN r...

We have completed a spectroscopic survey of X-ray point sources in eight low-redshift clusters of galaxies (0.05 < z < 0.31) and have identified 40 cluster members with broad-band (0.3–8 keV) X-ray luminosities between LX = 8×1040 and 4×1043 erg s−1. There are between two and ten X-ray sources per cluster. We use visible-wavelength emission lines, X-ray spectral shapes, and multiwavelength flux...

We have performed a spectroscopic study of 7 Type 2 QSOs using the mid-infrared spectrometer IRS on board the Spitzer Space Telescope. These are (to our knowledge) the first mid-IR spectra of X-ray selected QSO2s taken. The objects have been selected according to their high intrinsic luminosities and column densities in the X-rays. Their spectra strongly differ from template spectra of Type 2 A...

A large population of heavily obscured, Compton-thick AGN is predicted by AGN synthesis models for the cosmic X-ray background and by the “relic” super-massive black-hole mass function measured from local bulges. However, even the deepest X-ray surveys are inefficient to search for these elusive AGN. Alternative selection criteria, combining mid-infrared with near-infrared and optical photometr...