arXiv subjects

F. Brighenti

Publications and source records attributed to F. Brighenti.

41 records · Page 3Linked to original sources

arXiv2005

Temperature and Dark Matter profiles of Galaxy Groups

The Chandra and XMM data for a sample of 19 relaxed groups/poor clusters, covering the temperature range 1-3 keV and selected to have the best available data, reveal a remarkable similarity in their temperature profile: cool cores outside of which the temperatures reach a peak for radii less than 0.1 of the virial radius and then decline. We fitted the derived mass profiles using an NFW model, which provides a good fit to the data when accounting for the central galaxy in the inner region. The concentration parameters and virial masses are in the range c = 5-22 and M = 2 x 10^13 - 4 x 10^14 solar masses, in general agreement with the concentrations found in numerical simulations.

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arXiv2005

X-ray constraints on the dark matter profile of a very relaxed cluster of galaxies

We have analyzed an XMM-Newton observation of the cluster Abell 2589. Apart from a low-level asymmetry in the central region, the cluster appears very relaxed and does not show presence of a central AGN. We derived constraints for the radial temperature, density and, assuming hydrostatic equilibrium, mass profiles. We find that the best fit to the dark matter profile is given by the Sersic-like profile proposed by Navarro et al. (2004). The NFW model does not provide a good fit. We also tested whether the central stellar component could affect the profile through the adiabatic contraction model but were unable to distinguish it from a simple "dark matter + stars" modeling.

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arXiv2003

Three-dimensional simulations of the interstellar medium in dwarf galaxies - I. Ram pressure stripping

We present 3D hydrodynamic simulations of ram pressure stripping in dwarf galaxies. Analogous studies on this subject usually deal with much higher ram pressures, typical of galaxy clusters, or mild ram pressure due to the gas halo of the massive galactic companions. We extend over previous investigations by considering flattened, rotating dwarf galaxies subject to ram pressures typical of poor galaxy groups. We study the ram pressure effects as a function of several parameters such as galactic mass and velocity, ambient gas density, and angle between the galactic plane and the direction of motion. It turns out that this latter parameter plays a role only when the gas pressure in the galactic centre is comparable to the ram pressure. Despite the low values of the ram pressure, some dwarf galaxies can be completely stripped after 1-2 hundred of million years. This pose an interesting question on the aspect of the descents and, more in general, on the morphological evolution of dwarf galaxies. In cases in which the gas is not completely stripped, the propagation of possible galactic wind may be influenced by the disturbed distribution of the interstellar matter. We also consider the modification of the ISM surface density induced by the ram pessure and find that the resulting compression may trigger star formation over long time spans.

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arXiv2002

Far Infrared Emission from Elliptical Galaxies: NGC 4649, NGC 4472, and NGC 4636

We present ISOPHOT P32 oversampled maps and P37/39 sparse maps, of three bright elliptical galaxies in the Virgo Cluster. The maps reach the limiting sensitivity of the ISOPHOT instrument at 60, 100, 170 and 200 microns. Two elliptical galaxies show no emission at all far-IR ISOPHOT wavelengths at a level of few tens of mJy. The null detection provides a test of the evolution of dust in elliptical galaxies and its size distribution and composition. As previous studies have shown, in many elliptical galaxies both IRAS and ISO have detected mid-IR excess 6-15 micron emission relative to the stellar continuum indicating emission from circumstellar dust. Under the assumption that these dusty outflows from evolving red giant stars and planetary nebulae are continuously supplying dust to the interstellar medium, we have computed the infrared luminosity at the ISOPHOT bands appropriate for NGC4472. The null far-IR ISOPHOT observations exceed the far-IR flux expected from dust expelled from a normal old stellar population.

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arXiv1999

Galactic winds and circulation of the ISM in dwarf galaxies

We study, through 2D hydrodynamical simulations, the feedback of a starburst on the ISM of typical gas rich dwarf galaxies. The main goal is to address the circulation of the ISM and metals following the starburst. We assume a single-phase rotating ISM in equilibrium in the galactic potential generated by a stellar disk and a spherical dark halo. The starburst is assumed to occur in a small volume in the center of the galaxy, and it generates a mechanical power of 3.8e39 erg/s or 3.8e40 erg/s for 30 Myr. We found, consistently with previous investigations, that the galactic wind is not very effective in removing the ISM. The metal rich stellar ejecta, instead, may be efficiently expelled from the galaxy and dispersed in the intergalactic medium. Moreover, we found that the central region of the galaxy is always replenished with cold and dense gas after a few 100 Myr from the starbust, achieving the requisite for a new star formation event in 0.5-1 Gyr. The hydrodynamical evolution of galactic winds is thus consistent with the episodic star formation regime suggested by many chemical evolution studies. We also discuss the X-ray emission of these galaxies and find that the observable (emission averaged) abundance of the hot gas underestimates the real one if thermal conduction is effective. This could explain the very low hot gas metallicities estimated in starburst galaxies.

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