A simple yet effective model of galaxy mergers

TL;DR

This paper presents a simple yet effective model of galaxy mergers that explains observed galaxy scale relations and matches results from complex simulations, offering rapid insights into galaxy evolution.

Contribution

It introduces a simplified model combining infall models and the scalar Virial Theorem to interpret galaxy merger effects on scale relations, aligning with observational data.

Findings

The model reproduces the slopes, scatters, and curvatures of observed galaxy scale relations.

It matches the accuracy of complex cosmo-hydro-dynamical simulations.

The model provides rapid exploratory insights into galaxy evolution effects.

Abstract

In the context of the hierarchical formation of galaxies, we investigated the role played by mergers in shaping the scale relations of galaxies, that is the projections of their Fundamental Plane onto the \IeRe, \IeSig, \MRa\ and \Lsig\ planes. To this aim, we developed a simple model of multiple dry mergers among galaxies by suitably combing the formalism and properties of the so-called infall models of galaxy formation and evolution with the formalism of the scalar Virial Theorem. In this context, we mimicked the hierarchical formation of galaxies and generated simple models of galaxies undergoing a number mergers in the course of their evolution. The results are used to interpret the large scale simulations and the companion scale relations from observational and theoretical perspectives. The aim is to interpret the observational data of the MANGA and WINGS samples and the results of theoretical detailed numerical cosmo-hydro-dynamical simulations, such as Illustris-TNG100. In this context, we derived the above scale relations for our theoretical models and compared them with the observational counterparts from the MANGA and WINGS database, (and indirectly the large scale simulations of Illustris-TNG100). The multiple dry merging mechanism is able to explain all the main characteristics of the observed scale relations of galaxies, such as slopes, scatters, curvatures and zones of exclusion. The distribution of galaxies in these planes is continuously changing across time because of the merging activity and other physical processes, such as star formation, quenching, energy feedback, and so forth.} The precision of the present simple merger theory is comparable with that obtained by the modern cosmo-hydro-dynamical simulations, with the advantage of providing a rapid exploratory response on the consequences engendered by different physical effects.