arXiv subjects

Giovanni C. Baiesi Pillastrini

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

4 recordsLinked to original sources

arXiv2025

Did the Corona Borealis-A2142 supercluster binary-like system originate as a proto-cluster binary embedded in a primordial cloud of galaxies?

The formation of the giant binary-like system composed by the Corona Borealis and Abell 2142 superclusters is an intriguing conundrum of the formation of large scale structures since, from the observational point of view, it represents a rare peculiarity in the distribution of massive galaxy superclusters. Having a configuration similar to a giant binary system interconnected by a huge filament, it is likely one if not the unique case to date observed in the Local Universe. So a question arise: how and when did it form? Here, the CrB and A2142 system has been hypothesized to be a descendent of a primordial binary system composed of two close galaxy proto-clusters, the CrB and A2142, originated from two independent collapsing process within a dense cloud of galaxies. Then, assuming that at a certain point the decoupling occurred due to the interplay of gravity-antigravity of DE, they began to move away in radial motion from each other following the accelerate expansion of the Universe. In the context of the LCDM model a Newtonian approximation of the two body motion in presence of DE has been applied using current physical parameters of the CrB and A2142 system with the aim to calculate the look-back time at decoupling. Its compatibility with the era of formation of the primordial galaxy proto-clusters has been tested. The event of the binary decoupling happened in a time larger than the age of the Universe! Of course, after such a result the advanced hypothesis on the origins of the CrB-A2142 system can be rejected, but not the test of compatibility since the look-back time at the error lower limit is 12.5 Gys ( z = 4.5) largely consistent with observations.

astro-ph.CO↗

arXiv2016

Does the Corona Borealis Supercluster form a giant binary-like system?

The distribution of local gravitational potentials generated by a complete volume-limited sample of galaxy groups and clusters filling the Corona Borealis region has been derived to search for new gravitational hints in the context of clus-tering analysis unrevealed by alternative methodologies. Mapping such a distribution as a function of spatial positions, the deepest potential wells in the sample trace unambiguously the locations of the densest galaxy cluster clumps providing the physical keys to bring out gravitational features connected to the formation, composition and evolution of the major clustered structures filling that region. As expected, the three deepest potential wells found at Equatorial coordinates: (~ 230°, ~ 28°, z ~ 0.075), (~ 240°, ~ 27°, z ~ 0.09) and, (227°, 5.8°, z ~ 0.0788) correspond to massive superclusters of galaxy groups and clusters identified as the Corona Borealis, A2142 and Virgo-Serpent, respectively. However, the deepest isopotential contours around the Corona Borealis and A2142 superclusters seem to suggest a gravitational feature similar to a giant binary-like system connected by a filamentary structure. To a first approximation, it seems unlikely that this hypothesized system could be gravitationally bound.

astro-ph.CO↗

arXiv2013

A Fast and Simple Algorithm for Detecting Large Scale Structures

Aims: we propose a gravitational potential method (GPM) as a supercluster finder based on the analysis of the local gravitational potential distribution measured by fast and simple algorithm applied to a spatial distribution of mass tracers. Methodology: the GPM performs a two-step exploratory data analysis: first, it measures the comoving local gravitational potential generated by neighboring mass tracers at the position of a test point-like mass tracer. The computation extended to all mass tracers of the sample provides a detailed map of the negative potential fluctuations. The most negative gravitational potential is provided by the highest mass density or, in other words, the deeper is a potential fluctuations in a certain region of space and denser are the mass tracers in that region. Therefore, from a smoothed potential distribution, the deepest potential well detects unambiguously a high concentration in the mass tracer distribution. Second, applying a density contrast criterion to that mass concentration, a central bound core may be identify and quantify in terms of memberships and total mass. Results: using a complete volume-limited sample of galaxy clusters, a huge concentration of galaxy clusters has been detected. In its central region, 35 clusters seem to form a massive and bound core enclosed in a spherical volume of 51 Mpc radius. Conclusions: the substantial agreement of our findings compared with those obtained by different methodologies, confirms the GPM as a straightforward and powerful as well as fast cluster finder useful for analyzing large datasets.

astro-ph.CO↗

arXiv2009

On the Characteristic Isolation of Compact Subgroups within Loose Groups of Galaxies

We have explored the hypothesis that compact subgroups lying within dense environments as loose groups of galaxies, at a certain stage of their evolutionary history, could be influenced by the action of the tidal field induced by the gravitational potential of the whole system. We argue that empty rings observed in projection around many compact subgroups of galaxies embedded in larger hosts originate around the spherical surface drawn by the tidal radius where the internal binding force of the compact subgroup balances the external tidal force of the whole system. This effect would torn apart member galaxies situated in this region determining a marked isolation of the subgroups from the rest of the host groups. If so, subsequent evolution of these subgroups should not be affected by external influences as the infall of new surrounding galaxies on them. Following this idea we have developed a statistical method of investigation and performed an application to show evidences of such effect studying a loose group of galaxies hosting a compact group in its central region. The system UZC 578 / HCG 68 seems to be a fair example of such hypothesized process.

astro-ph.CO↗