Searcharxiv⌕ Search

arXiv subjects

G. C. Baiesi Pillastrini

Publications and source records attributed to G. C. Baiesi Pillastrini.

4 recordsLinked to original sources

On the giant supercluster binary-like system formed by the Corona Borealis and Abell 2142

The recent hypothesis of a giant supercluster binary-like structure formed by the Corona Borealis and its close companion Abell 2142 (supercluster) belongs to a little known area of investigation as the dynamics of gravitationally interacting galaxy supercluster pairs. From the observational point of view this structure approximates the configuration of a binary-like system in linear orbit interconnected by a huge filamentary structure which, if confirmed, it would be the first case to date observed at z > 0.07. Given the importance to disentangle this issue, a follow-up analysis has been performed on the region constrained by the common envelop of the two superclusters in order to search for new hints to confirm their mutual gravitational interaction. Observational signatures of that interaction have been found mapping the inner peculiar motions where the observed negative peculiar velocities measured within the A2142 (supercluster) region suggest a general matter flow toward the Corona Borealis supercluster. Besides, analyzing the effects on both superclusters due to the mutual impact of the external tidal forces, turns out that their inner dynamics remain unperturbed up to the turnaround radii. Outside, where the binding forces are overlapped by the tidal ones, the outskirts of both superclusters should be unstable and subject to fragmentation. Such a scenario indicates that both superclusters interact with comparable and reciprocal tidal perturbations leaving the whole system in a substantial dynamical equilibrium. The origin of such a dynamical dichotomy would be explained either by a much more massive Corona Borealis supercluster than that estimated in the present work or by a selection effect biasing the small sample of peculiar velocities due to the remoteness of the system worsened by the large uncertainty on their measurements.

astro-ph.CO↗

On the Adromeda to Milky Way mass-ratio

We have explored the hypothesis that the total mass-ratio of the two main galaxies of the Local Group: Andromeda Galaxy(M31) and the Milky Way (MW) can be constrained measuring the tidal force induced by the surrounding mass distribution, M31 included, on the MW. We argue that the total mass-ratio between the two groups can be approximated, at least qualitatively, finding the tidal radius where the internal binding force of the MW balances the external tidal force acting on it. Since M31 is the massive tidal perturber of the local environment, we have used a wide range of M31 to MW mass-ratio combinations to compute the corresponding tidal radii. Of them, only few match the distance of the zero-tidal shell i.e. the shell identified observationally by the outermost dwarf galaxies which do not show any sign of tidal effects. This is the key to constrain the best mass-ratio interval of the two galaxies. Our results favour a solution where the mass-ratio ranges from 2 to 3 implying a massive predominance of M31.

astro-ph.CO↗

A Compilation of Redshifts for Compact Groups of Galaxies

We present a compilation of redshifts for 4,911 Compact Groups of galaxies (CG) referenced to the heliocentric reference frame, where 694 of them are available from the literature as of 1992. An unpublished redshift list for 4,217 CGs identified in the SDSS data release 4 by Deng et al. (2006) has been added too. We present an additional list of 157 CGs with published redshifts for one or more member galaxies and 13 apparent CGs with discrepant memberships. The electronic version of the compilation is provided by email request.

astro-ph↗

A Method to Constrain the Total Mass of Galaxy Groups

We present a simple method to constrain the total mass of groups of galaxies. Tidal theory predicts that a limit to the mass of bound groups of galaxies can be obtained by using the fact that the tidal forces due to the external mass distributions are insufficient to disrupt the groups. To illustrate how the method works, we find tidal limits on the mass of eleven nearby galaxy groups. In most cases, tidal limits placed on these groups show that mass estimations obtained from methods based either on the application of the virial theorem or moments of the projected mass are underestimated by a factor of about 2 even if, in many cases, errors are large. Three groups show virial parameters fully concordant with the tidal constraints while two outlier groups show anomalous results. The irregular state of the latter suggests that the reliability of the method depends on the physical properties of the test groups, which should match the fundamental assumptions of spherical symmetry and dynamical equilibrium state.

astro-ph↗