Dynamical models for dusty disk galaxies

Disk galaxies contain a large amount of interstellar dust, which affects the projection of kinematic quantities. We investigate in detail the effects of dust extinction on the mean projected velocity and the projected velocity dispersion. We use our results to construct a general strategy to determine the dynamical structure of disk galaxies, with the aim to constrain their mass distribution and dynamical history.Comment: to be published in the proceedings of "Galaxy Disks and Disk Galaxies", Funes J.G. and Corsini E.M. eds., ASP Conference Serie

Spherical cosmological models: an alternative cosmology

The properties of universes are explored that are entirely in the interior of black holes. It is argued that these models offer a paradigm that may shed a new light on old cosmological problems. The topics that are addressed include: geometry of the universes, evolution, relation to the concordance model, dark matter, dark energy, mass ejection from black holes, galaxy models with a central black hole, Mach's principle

Dynamical models of NGC 3115

We present new dynamical models of the S0 galaxy N3115, making use of the available published photometry and kinematics as well as of two-dimensional TIGER spectrography. We first examined the kinematics in the central 40 arcsec in the light of two integral f(E,J) models. Jeans equations were used to constrain the mass to light ratio, and the central dark mass whose existence was suggested by previous studies. The even part of the distribution function was then retrieved via the Hunter & Qian formalism. We thus confirmed that the velocity and dispersion profiles in the central region could be well fit with a two-integral model, given the presence of a central dark mass of ~10^9 Msun. However, no two integral model could fit the h_3 profile around a radius of 25 arcsec where the outer disc dominates the surface brightness distribution. Three integral analytical models were therefore built using a Quadratic Programming technique. These models showed that three integral components do indeed provide a reasonable fit to the kinematics, including the higher Gauss-Hermite moments. Again, models without a central dark mass failed to reproduce the observed kinematics in the central arcseconds. This clearly supports the presence of a nuclear black hole of at least 6.5 10^8 Msun in the centre of NGC 3115. These models were finally used to estimate the importance of the dark matter in the outer part of NGC 3115, suggested by the flat stellar rotation curve observed by Capaccioli et al. (1993).Comment: 18 pages, 22 figures, accepted for publication in MNRA

Tracing the relation between black holes and dark haloes

We present new velocity dispersion measurements for a set of 12 spiral galaxies and use them to derive a more accurate V_c - sigma relation which holds for a wide morphological range of galaxies. Combined with the M_BH - sigma relation, this relation can be used as a tool to estimate supermassive black hole (SMBH) masses by means of the asymptotic circular velocity. Together with the Tully-Fisher relation, it serves as a constraint for galaxy formation and evolution models.Comment: 2 pages, 2 figures, to appear in Proc. IAU Symp. 220, "Dark Matter in Galaxies" eds. S. Ryder, D.J. Pisano, M. Walker, & K. Freeman (San Francisco: ASP

Completely analytical families of anisotropic gamma-models

We present new analytical distribution functions for anisotropic spherical galaxies. They have the density profiles of the gamma-models, which allow a wide range of central density slopes, and are widely used to fit elliptical galaxies and the bulges of spiral galaxies. Most of our models belong to two two-parameter families. One of these parameters is the slope gamma of the central density cusp. The other allows a wide range of varying radial and tangential anisotropies, at either small or large radii. We give analytical formulas for their distribution functions, velocity dispersions, and the manner in which energy and transverse velocity are distributed between orbits. We also give some of their observable properties, including line-of-sight velocity profiles which have been computed numerically. Our models can be used to provide a useful tool for creating initial conditions for N-body and Monte Carlo simulations.Comment: 21 pages, 15 figures, accepted for publication in MNRA

Dynamical models linking BH masses and DM content

We investigate the relation between the dark matter distribution of galaxies and their central supermassive black holes which is suggested by the v_c-sigma relation. Since early-type galaxies appear to have larger black holes than late-type ones, we look for an equivalent pattern in the dark matter distribution as a function of Hubble type. To achieve our goal we use a state-of-the-art modelling code that allows a variety of geometries to be fitted to a combination of radio and optical observations of galaxies with different morphology.Comment: 2 pages, 2 figures, contributed paper to Proceedings of the Conference "Growing Black Holes" held in Garching, Germany, June 21-25, 2004, edited by A. Merloni, S. Nayakshin and R. Sunyaev, Springer-Verlag series of "ESO Astrophysics Symposia

N-body/SPH study of the evolution of dwarf galaxies in a cluster environment

Using an N-body/SPH code, we explore the scenario in which a dwarf elliptical galaxy (dE) is subjected to ram-pressure stripping due to the intracluster medium (ICM). Our simulations show that while (i) smaller dEs lose their ISM almost immediately after entering the cluster, (ii) more massive dEs are able to retain their gas for considerable timespans.Comment: 1 page, no figures, poster contribution to the Splinter Meeting "Galaxies in interaction" at the joint meeting of the Czech Astronomical Society and the Astronomische Gesellschaft (20-25 Sept. 2004, Prague, Czech Republic

Dark matter halos around elliptical galaxies: how reliable is the stellar kinematical evidence ?

Hierarchical models of galaxy formation and various observational evidence suggest that elliptical galaxies are, like disk galaxies, embedded in massive dark matter halos. Stellar kinematics are considered the most important tracer for this dark halo at a few effective radii. Using detailed modeling techniques, several authors have recently presented stellar kinematical evidence of a dark halo for a number of elliptical galaxies. In these modeling techniques, dust attenuation (absorption and scattering of starlight by dust grains) has not been taken into account. Nevertheless, elliptical galaxies contain a significant amount of interstellar dust, which affects all observable quantities, including the observed kinematics. We constructed a set of dynamical models for elliptical galaxies, in which dust attenuation is included through a Monte Carlo technique. We find that a dust component, shallower than the stellar distribution and with an optical depth of order unity, affects the observed kinematics significantly, in the way that it mimics the presence of a dark halo. If such dust distributions are realistic in elliptical galaxies, we are faced with a new mass-dust degeneracy. Taking dust into account in dynamical modeling procedures will hence reduce or may even eliminate the need for a dark matter halo at a few effective radii.Comment: 5 pages, 4 figures, accepted for publication in ApJ Letters. Uses emulateapj5.sty. Typos are correcte

The Hernquist model revisited: completely analytical anisotropic dynamical models

Simple analytical models, such as the Hernquist model, are very useful tools to investigate the dynamical structure of galaxies. Unfortunately, most of the analytical distribution functions are either isotropic or of the Osipkov-Merritt type, and hence basically one-dimensional. We present three different families of anisotropic distribution functions that self-consistently generate the Hernquist potential-density pair. These families have constant, increasing and decreasing anisotropy profiles respectively, and can hence represent a wide variety of orbital structures. For all of the models presented, the distribution function and the velocity dispersions can be written in terms of elementary functions. These models are ideal tools for a wide range of applications, in particular to generate the initial conditions for N-body or Monte Carlo simulations.Comment: 14 pages, 7 figures, accepted for publication in A&A - formulae (51) and (54) and figure 4 correcte