Vazza F.,Jacobs University Bremen |
Vazza F.,National institute for astrophysics |
Roncarelli M.,University of Bologna |
Roncarelli M.,Roche Holding AG |
And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011
We study the azimuthal scatter in the radial profiles of X-ray luminous galaxy clusters with two sets of high-resolution cosmological re-simulations obtained with the codes enzo and gadget2. The average gas profiles are computed for different angular sectors of the cluster projected volume and compared with the mean cluster profiles at each radius from the centre. We report that, in general, the level of azimuthal scatter is found to be ∼10per cent for gas density, temperature and entropy inside R200, and ∼25per cent for X-ray luminosity for the same volume. These values generally double approaching 2R200 from the cluster centre, and are generally found to be higher (by ∼20-40per cent) in the case of perturbed systems. A comparison with the results from recent Suzaku observations is discussed, showing the possibility to simply interpret the large azimuthal scatter of observables in light of our simulated results. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source
Monaco L.,University of Concepcion |
Monaco L.,European Southern Observatory |
Bonifacio P.,University Paris Diderot |
Sbordone L.,Max Planck Institute for Astrophysics |
And 2 more authors.
Astronomy and Astrophysics | Year: 2010
Context. A discrepancy has emerged between the cosmic lithium abundance inferred by the WMAP satellite measurement coupled with the prediction of the standard big-bang nucleosynthesis theory, and the constant Li abundance measured in metal-poor halo dwarf stars (the so-called Spite plateau). Several models are being proposed to explain this discrepancy, involving either new physics, in situ depletion, or the efficient depletion of Li in the pristine Galaxy by a generation of massive first stars. The realm of possibilities may be narrowed considerably by observing stellar populations in different galaxies, which have experienced different evolutionary histories. Aims. The ω Centauri stellar system is commonly considered as the remnant of a dwarf galaxy accreted by the Milky Way. We investigate the lithium content of a conspicuous sample of unevolved stars in this object. Methods. We obtained moderate resolution (R = 17 000) spectra for 91 main-sequence/early sub-giant branch (MS/SGB) ω Cen stars using the FLAMES-GIRAFFE/VLT spectrograph. Lithium abundances were derived by matching the equivalent width of the Li i resonance doublet at 6708 Å to the prediction of synthetic spectra computed with different Li abundances. Synthetic spectra were computed using the SYNTHE code along with ATLAS-9 model atmospheres. The stars effective temperatures are derived by fitting the wings of the Hα line with synthetic profiles. Results. We obtain a mean content of A(Li) = 2.19 ± 0.14 dex for ω Centauri MS/SGB stars. This is comparable to what is observed in Galactic halo field stars of similar metallicities and temperatures. Conclusions. The Spite plateau seems to be an ubiquitous feature of old, warm metal-poor stars. It exists also in external galaxies, if we accept the current view about the origin of ω Cen. This implies that the mechanism(s) that causes the "cosmological lithium problem" may be the same in the Milky Way and other galaxies. © 2010 ESO. Source
Schipani P.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte |
Arcidiacono C.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Bologna |
Argomedo J.,European Southern Observatory |
Dall'Ora M.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte |
And 6 more authors.
Review of Scientific Instruments | Year: 2012
The VLT survey telescope is the latest telescope installed at European Southern Observatorys Paranal observatory that is considered one of the best sites for optical astronomy for the excellent seeing conditions. The exceptional quality of the site imposes tight requirements for the telescope tracking system that shall perform very well to fully exploit the extreme sharpness of the Chilean sky. We describe the specific solutions adopted for pointing, servo and guiding systems and the results obtained during the commissioning of the telescope. The hardware implementation relies on industry components and the control solutions privilege both the performance and the future maintainability of the system. © 2012 American Institute of Physics. Source
Gruppioni C.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Bologna |
Berta S.,Max Planck Institute for Extraterrestrial Physics |
Spinoglio L.,Istituto di Astrofisica Spaziale e Fisica Cosmica |
Pereira-Santaella M.,CSIC - National Institute of Aerospace Technology |
And 9 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016
We present new estimates of AGN accretion and star formation (SF) luminosity in galaxies obtained for the local 12 μm sample of Seyfert galaxies (12MGS), by performing a detailed broad-band spectral energy distribution (SED) decomposition including the emission of stars, dust heated by SF and a possible AGN dusty torus. Thanks to the availability of data from the X-rays to the sub-millimetre, we constrain and test the contribution of the stellar, AGN and SF components to the SEDs. The availability of Spitzer-InfraRed Spectrograph (IRS) low-resolution mid-infrared (mid-IR) spectra is crucial to constrain the dusty torus component at its peak wavelengths. The results of SED fitting are also tested against the available information in other bands: the reconstructed AGN bolometric luminosity is compared to those derived from X-rays and from the high excitation IR lines tracing AGN activity like [Ne
Forster Schreiber N.M.,Max Planck Institute for Extraterrestrial Physics |
Genzel R.,Max Planck Institute for Extraterrestrial Physics |
Genzel R.,University of California at Berkeley |
Newman S.F.,University of California at Berkeley |
And 30 more authors.
Astrophysical Journal | Year: 2014
We report the detection of ubiquitous powerful nuclear outflows in massive (≥1011 M ) z 2 star-forming galaxies (SFGs), which are plausibly driven by an active galactic nucleus (AGN). The sample consists of the eight most massive SFGs from our SINS/zC-SINF survey of galaxy kinematics with the imaging spectrometer SINFONI, six of which have sensitive high-resolution adaptive optics-assisted observations. All of the objects are disks hosting a significant stellar bulge. The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM 1500 km s-1, [N II]/Hα ratio 0.6, and intrinsic extent of 2-3 kpc. These properties are consistent with warm ionized gas outflows associated with Type 2 AGN, the presence of which is confirmed via independent diagnostics in half the galaxies. The data imply a median ionized gas mass outflow rate of 60 M yr-1 and mass loading of 3. At larger radii, a weaker broad component is detected but with lower FWHM 485 km s -1 and [N II]/Hα 0.35, characteristic for star formation-driven outflows as found in the lower-mass SINS/zC-SINF galaxies. The high inferred mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Larger samples at high masses will be crucial in confirming the importance and energetics of the nuclear outflow phenomenon and its connection to AGN activity and bulge growth. © 2014. The American Astronomical Society. All rights reserved.. Source