Exploring the connection between stellar halo profiles and accretion histories in $L_*$ galaxies

TL;DR

This study uses simulations and Monte Carlo methods to analyze how the accretion history influences the density profiles of stellar halos in $L_*$ galaxies, revealing the role of satellite mass and dynamical friction.

Contribution

It introduces a novel combination of N-body simulations, particle tagging, and Monte Carlo accretion histories to connect stellar halo profiles with galaxy accretion events.

Findings

More massive satellites deposit stars deeper into the host.

Stellar halos show a negative gradient in satellite-to-host mass ratio with radius.

Largest stellar halos result from a few massive satellite accretions.

Abstract

I use a library of controlled minor merger N-body simulations, a particle tagging technique and Monte Carlo generated $\Lambda$CDM accretion histories to study the highly stochastic process of stellar deposition onto the accreted stellar halos (ASHs) of $L_*$ galaxies. I explore the main physical mechanisms that drive the connection between the accretion history and the density profile of the ASH. I find that: i) through dynamical friction, more massive satellites are more effective at delivering their stars deeper into the host; ii) as a consequence, ASHs feature a negative gradient between radius and the local mass-weighed virial satellite-to-host mass ratio; iii) in $L_*$ galaxies, most ASHs feature a density profile that steepens towards sharper logarithmic slopes at increasing radii, though with significant halo-to-halo scatter; iv) the ASHs with the largest total ex-situ mass are such because of the chance accretion of a small number of massive satellites (rather than of a large number of low-mass ones).