The Intergalactic Stellar Population from Mergers of Elliptical Galaxies with Dark Matter halos

TL;DR

This paper uses simulations to study how elliptical galaxy mergers with dark matter halos produce intergalactic stellar populations, revealing that dark halos influence the amount of unbounded stars and intergalactic light.

Contribution

It introduces detailed simulations of elliptical galaxy mergers with dark matter halos, showing how dark matter affects intergalactic star production and comparing results with previous models without dark halos.

Findings

Hyperbolic encounters produce more unbounded luminous particles.

Lower mass-to-light ratios lead to larger unbounded stellar fractions.

Intergalactic luminosity fractions are around 4-6%, lower than previous models without dark halos.

Abstract

We present simulations of dry-merger encounters between pairs of elliptical galaxies with dark matter halos. The aim of these simulations is to study the intergalactic stellar populations produced in both parabolic and hyperbolic encounters. We model progenitor galaxies with total-to-luminous mass ratios M_T/M_L 3 and 11. The initial mass of the colliding galaxies are chosen so that M_1/M_2 and 10. The model galaxies are populated by particles representing stars, as in Stanghellini et al. (2006), and dark matter. Merger remnants resulting from these encounters display a population of unbounded particles, both dark and luminous. The number of particles becoming unbounded depends on orbital configuration, with hyperbolic encounters producing a larger luminous intracluster population than parabolic encounters. Furthermore, in simulations with identical orbital parameters, a lower M_T/M_L of the colliding galaxies produces a larger fraction of unbounded luminous particles. For each modeled collision, the fraction of unbounded to initial stellar mass is the same in all mass-bins considered, similarly to what we found previously by modeling encounters of galaxies without dark halos. The fraction of intergalactic to total luminosity resulting from our simulations is ~ 4% and ~ 6% for dark-to-bright mass rations of 10 and 2 respectively. These unbounded-to-total luminous fractions are down from 17 % that we had previously found in the case of no dark halos. Our results are in broad agreement with intergalactic light observed in groups of galaxies, while the results of our previous models without dark halos better encompass observed intracluster populations. We suggest a possible formation scenario of intergalactic stars.