European Southern Observatory

About: European Southern Observatory is a facility organization based out in Garching bei München, Germany. It is known for research contribution in the topics: Galaxy & Stars. The organization has 3594 authors who have published 16157 publications receiving 823095 citations. The organization is also known as: The European Southern Observatory，ESO & ESO.

The relation between AGN hard X-ray emission and mid-infrared continuum from ISO spectra: Scatter and unification aspects ,

Abstract: We use mid-infrared spectral decomposition to separate the 6 µm mid-infrared AGN continuum from the host emission in the ISO low resolution spectra of 71 active galaxies and compare the results to observed and intrinsic 2−10 keV hard X-ray fluxes from the literature. We find a correlation between mid-infrared luminosity and absorption corrected hard X-ray luminosity, but the scatter is about an order of magnitude, significantly larger than previously found with smaller statistics. Main contributors to this scatter are likely variations in the geometry of absorbing dust, and AGN variability in combination with non-simultaneous observations. There is no significant difference between type 1 and type 2 objects in the average ratio of mid- infrared and hard X-ray emission, a result which is not consistent with the most simple version of a unified scheme in which an optically and geometrically thick torus dominates the mid-infrared AGN continuum. Most probably, significant non-torus contributions to the AGN mid-IR continuum are masking the expected difference between the two types of AGN.

Line-strength gradients in elliptical galaxies

Abstract: We have measured line-strength indices as a function of radius in several elliptical galaxies. All of them show strong radial gradients in Mg, but much weaker gradients in Fe and Hs. The isophotes and contours of constant line-strength have the same flattening. More luminous galaxies have shallower gradients, contrary to the prediction of models of dissipative collapse. Most of the galaxies observed show weak central emission which can partially fill the Balmer absorption lines.

Evidence for powerful AGN winds at high redshift: dynamics of galactic outflows in radio galaxies during the “Quasar Era”

Abstract: AGN feedback now appears as an attractive mechanism to resolve some of the outstanding problems with the “standard” cosmological models, in particular those related to massive galaxies. At low redshift, evidence is growing that gas cooling and star formation may be efficiently suppressed by mechanical energy input from radio sources. To directly constrain how this may influence the formation of massive galaxies near the peak in the redshift distribution of powerful quasars, z ∼ 2, we present an analysis of the emission-line kinematics of 3 powerful radio galaxies at z ∼ 2−3 (HzRGs) based on rest-frame optical integral-field spectroscopy obtained with SINFONI on the VLT. The host galaxies of powerful radio-loud AGN are among the most massive galaxies, and thus AGN feedback may have a particularly clear signature in these galaxies. We find evidence for bipolar outflows in all HzRGs, with kinetic energies that are equivalent to 0.2% of the rest-mass of the supermassive black hole. Observed total velocity offsets in the outflows are ∼800−1000 km s −1 between the blueshifted and redshifted line emission, and FWHMs ∼ 1000 km s −1 suggest strong turbulence. Line ratios allow to measure electron temperatures, ∼10 4 K from [OIII]λλλ4363, 4959, 5007 at z ∼ 2, electron densities (∼500 cm −3 ) and extinction (AV ∼ 1−4 mag). Ionized gas masses estimated from the Hα luminosity are of order 10 10 M� , similar to the molecular gas content of HzRGs, underlining that these outflows may indicate a significant phase in the evolution of the host galaxy. The total energy release of ∼10 60 erg during a dynamical time of ∼10 7 yrs corresponds to about the binding energy of a massive galaxy, similar to the prescriptions adopted in galaxy evolution models. Geometry, timescales and energy injection rates of order 10% of the kinetic energy flux of the jet suggest that the outflows are most likely driven by the radio source. The global energy density release of ∼10 57 erg s −1 Mpc −3 may also influence the subsequent evolution of the HzRG by enhancing the entropy and pressure in the surrounding halo and facilitating ram-pressure stripping of gas in satellite galaxies that may contribute to the subsequent mass assembly of the HzRG through low-dissipation “dry” mergers.

XMM-Newton observation of the lockman hole. I. The X-ray data

Abstract: We report on the first deep X-ray survey with the XMM-Newton observatory during the performance verification phase. The field of the Lockman Hole, one of the best studied sky areas over a very wide range of wavelengths, has been observed. A total of ~100 ksec good exposure time has been accumulated. Combining the images of the European Photon Imaging Camera (EPIC) detectors we reach a flux limit of 0.31, 1.4 and , respectively in the 0.5-2, 2-10, and 5-10 keV band. Within an off-axis angle of 10 arcmin we detect 148, 112 and 61 sources, respectively. The log(N )-log(S ) relation in the three bands is compared with previous results. In particular in the 5-10 keV band these observations present the deepest X-ray survey ever, about a factor 20 more sensitive than the previous BeppoSAX observations. Using X-ray spectral diagnostics and the set of previously known, spectroscopically identified ROSAT sources in the field, the new sources can be classified. XMM-Newton detects a significant number (~40% ) of X-ray sources with hard, probably intrinsically absorbed X-ray spectra, confirming a prediction of the population synthesis models for the X-ray background.

H0LiCOW – I. H0 Lenses in COSMOGRAIL's wellspring: program overview

Abstract: Strong gravitational lens systems with time delays between the multiple images allow measurements of time-delay distances, which are primarily sensitive to the Hubble constant that is key to probing dark energy, neutrino physics and the spatial curvature of the Universe, as well as discovering new physics. We present H0LiCOW (H-0 Lenses in COSMOGRAIL's Wellspring), a program that aims to measure H-0 with <3.5 per cent uncertainty from five lens systems (B1608+ 656, RXJ1131-1231, HE 0435-1223, WFI2033-4723 and HE 1104-1805). We have been acquiring (1) time delays through COSMOGRAIL and Very Large Array monitoring, (2) high-resolution Hubble Space Telescope imaging for the lens mass modelling, (3) wide-field imaging and spectroscopy to characterize the lens environment and (4) moderate-resolution spectroscopy to obtain the stellar velocity dispersion of the lenses for mass modelling. In cosmological models with one-parameter extension to flat Lambda cold dark matter, we expect to measure H-0 to <3.5 per cent in most models, spatial curvature Omega(k) to 0.004, w to 0.14 and the effective number of neutrino species to 0.2 (1s uncertainties) when combined with current cosmic microwave background (CMB) experiments. These are, respectively, a factor of similar to 15, similar to 2 and similar to 1.5 tighter than CMB alone. Our data set will further enable us to study the stellar initial mass function of the lens galaxies, and the co-evolution of supermassive black holes and their host galaxies. This program will provide a foundation for extracting cosmological distances from the hundreds of time-delay lenses that are expected to be discovered in current and future surveys.