Silvia Pellegrini

Winds, outflows, and inflows in X-ray elliptical galaxies. I

The novel class of 1D hydrodynamical evolutionary sequences for gas flows in elliptical galaxies presented employs model galaxies whose virialized density distributions are constrained to lie on their fundamental plane. The models evolve through as many as three consecutive (wind, outflow, inflow) evolutionary stages. These evolutionary sequences indicate that the X-ray-faint galaxies are still in their wind phase, while the bulk of ellipticals are in the outflow phase, and a few of the brightest galaxies may already have undergone transition to the inflow regime. The effects of interactions with the intracluster medium, ram pressure, encounters, and merging events are qualitatively discussed. 114 refs.

Production and circulation of iron in elliptical galaxies and clusters of galaxies

We introduce the concept of cluster iron mass-to-light ratio (IMLR) and estimate its value for both the intracluster medium and the stars, finding the amount of iron to be nearly the same in the two cluster components. We discuss under which conditions the past supernova activity can account for the observed IMLR and provide evidence that either the past average rate of Type Ia supernovae was at least a factor of ∼10 higher than the present rate in ellipticals, or massive stars in clusters formed with a very flat initial mass function (IMF)

Accretion and Nuclear Activity of Quiescent Supermassive Black Holes. I. X-Ray Study

We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~1038-1039 ergs s-1 (LX/LEdd ~ 10-8 to 10-7) and colors or spectra consistent with accreting supermassive black holes (SMBHs), except for the nucleus of NGC 4486B, which is softer than typical AGN spectra. In a few cases, the X-ray morphology of the nuclear sources shows hints of marginally extended structures, in addition to the surrounding diffuse thermal emission from hot gas, which is detectable on scales 1 kpc. In one case (NGC 5845), a dusty disk may partially obstruct our direct view of the SMBH. We have estimated the temperature and density of the hot interstellar medium, which is one major source of fuel for the accreting SMBH; typical central densities are ne ≈ (0.02 ± 0.01) cm-3. Assuming that the hot gas is captured by the SMBH at the Bondi rate, we show that the observed X-ray luminosities are too faint to be consistent with standard disk accretion, but brighter than predicted by radiatively inefficient solutions (e.g., advection-dominated accretion flows [ADAFs]). In total, there are ≈20 galaxies for which SMBH mass, hot gas density, and nuclear X-ray luminosity are simultaneously known. In some cases, the nuclear sources are brighter than predicted by the ADAF model; in other cases, they are consistent or fainter. We discuss the apparent lack of correlations between Bondi rate and X-ray luminosity and suggest that, in order to understand the observed distribution, we need to know two additional parameters: the amount of gas supplied by the stellar population inside the accretion radius, and the fraction (possibly 1) of the total gas available that is accreted by the SMBH. We leave a detailed study of these issues to a subsequent paper.

The stellar initial mass function of early-type galaxies from low to high stellar velocity dispersion: homogeneous analysis of atlas3D and Sloan Lens ACS galaxies

We present an investigation about the shape of the initial mass function (IMF) of early-type galaxies (ETGs), based on a joint lensing and dynamical analysis, and on stellar population synthesis models, for a sample of 55 lens ETGs identified by the Sloan Lens ACS (SLACS) Survey. We construct axisymmetric dynamical models based on the Jeans equations which allow for orbital anisotropy and include a dark matter halo. The models reproduce in detail the observed \textit{HST} photometry and are constrained by the total projected mass within the Einstein radius and the stellar velocity dispersion (

Hot Interstellar Matter in Elliptical Galaxies

\sigma

Reconciling optical and X-ray mass estimates: the case of the elliptical galaxy NGC 3379

) within the SDSS fibers. Comparing the dynamically-derived stellar mass-to-light ratios

The energetics of flat and rotating early-type galaxies and their X-ray luminosity

(M_*/L)_{\rm dyn}

Transient Low-mass X-ray Binary Populations in Elliptical Galaxies NGC 3379 and NGC 4278

, obtained for an assumed halo slope

THE SPECTRAL AND TEMPORAL PROPERTIES OF TRANSIENT SOURCES IN EARLY-TYPE GALAXIES

\rho_{\rm h}\propto r^{-1}

The effects of galaxy shape and rotation on the X-ray haloes of early-type galaxies – II. Numerical simulations

, to the stellar population ones