Found 32 talks width keyword active galaxies

Supermassive black holes are ubiquitous in galaxies and play a fundamental role in their life cycle. I will review observational progress in defining and refining the various empirical scaling relations between black hole masses and host galaxy properties. I will emphasize ways in which the intrinsic scatter of the scaling relations can be quantified, and present evidence that the scatter correlates with physical properties. I will describe how the scaling relations can be extended to active galaxies and summarize preliminary efforts to probe the evolution of these scaling relations with redshift. I will present new measurements of the cold ISM content in AGN host galaxies and constraints they place on currently popular models of AGN feedback. Lastly, I will discuss a new class of low-mass black holes in bulgeless and dwarf galaxies that serve as local analogs of seed supermassive black holes.

Luminous Infrared Galaxies (LIR=10^11-10^12Lsun) have star formation rates in the range of ~20-200Msun/yr. In the local Universe ~50% LIRGs show AGN or AGN/SB composite nuclear activity from optical spectroscopy. We decompose Spitzer/IRS 5-35micron spectra of a complete sample of 50 local (d<75Mpc) LIRGs using SB and AGN clumpy torus model templates. We derive a mid-IR AGN detection rate in our sample of local LIRGs of 50%. We also compare the continuum mid-IR AGN detection with other indicators in the mid-IR, optical and X-rays. We estimate for the first time the AGN bolometric contribution to the IR luminosity of the galaxies in local LIRGs. We find that one-third of local LIRGs have LAGN(bol)/LIR>0.05, with only ~10% having a significant contribution LAGN(bol)/LIR>0.25. This is in line with results of Nardini et al. (2010) that only at LIR>3x10^12Lsun the AGN starts dominating bolometrically the IR luminosity in the majority of the systems.

Relativistic jets in AGN in general, and in blazars in particular, are the most energetic and among the most powerful astrophysical objects known so far. Their relativistic nature provides them the ability to emit profusely in all spectral ranges from radio wavelengths to gamma-rays, as well as abrupt variability in all time scales (from hours to years). Since the birth of gamma-ray astronomy, locating the origin of gamma-ray emission has been a fundamental problem for the knowledge of the emission processes involved. Deep and densely time sampled monitoring programs with the Fermi Gamma-ray Space Telescope and several other facilities at most of the available spectral ranges (including polarization measurements where possible) are starting to shed light for the case of blazars. After a short review of the status of the problem, some of the latest results locating the GeV emission in the jets of some blazars, at >10 parsec from the central AGN engine, will be presented together with their implications about the gamma-ray emission mechanisms involved

The MAGIC telescopes discovered very high energy (VHE, E>100 GeV) gamma-ray emission coming from the distant Flat Spectrum Radio Quasar (FSRQ) PKS 1222+21 (4C +21.35, z=0.432). It is the second most distant VHE gamma-ray source, with well measured redshift, detected until now. The detection coincides with high energy MeV/GeV gamma-ray activity measured by the Large Area Telescope (LAT) on board the Fermi satellite. The VHE and MeV/GeV spectra, corrected for the absorption by the extragalactic background light, can be described by a single power law with photon index 2.72 ± 0.34 between 3 GeV and 400 GeV, consistent with gamma-ray emission belonging to a single component in the jet. The absence of a spectral cutoff constrains the gamma-ray emission region to lie outside the Broad Line Region, which would otherwise absorb the VHE gamma-rays. On the other hand, the MAGIC measurement of a doubling time of about 9 minutes indicates an extremely compact emission region, in conflict with the "far dissipation" scenario. This result challenges jet emission models in FSRQs and indicates the importance of jet sub-structures.

I will present new mid-infrared imaging data for a sample of ~20 nearby Seyfert galaxies obtained with T-ReCS and MICHELLE on the Gemini Telescopes at subarcsecond resolution. Our aim is to compare the properties of Type-1 and Type-2 Seyfert tori using clumpy torus models and a Bayesian approach to fit the infrared nuclear spectral energy distributions (SEDs). These dusty tori have physical sizes smaller than 10 pc radius, as derived from our fits. Unification schemes of AGN account for a variety of observational differences in terms of viewing geometry. However, we find evidence that strong unification may not hold, and that the immediate dusty surroundings of Type-1 and Type-2 Seyfert nuclei are intrinsically different. The Type-2 tori studied here are broader, have more clumps, and these clumps have lower optical depths than those of Type-1 tori. The larger the covering factor of the torus, the smaller the probability of having direct view of the AGN, and vice-versa. In our sample, Seyfert 2 tori have larger covering factors and smaller escape probabilities than those of Seyfert 1. Thus, on the basis of the results presented here, the classification of a Seyfert galaxy as a Type-1 or Type-2 depends more on the intrinsic properties of the torus rather than on its mere inclination, in contradiction with the simplest unification model.