Concurrent infall of satellites: Collective effects changing the overall picture

TL;DR

This study uses N-body simulations to investigate how multiple satellites sinking simultaneously in a dark matter halo influence each other's orbital decay, revealing collective effects that alter their accretion histories and challenge traditional isolated models.

Contribution

It introduces the first detailed analysis of collective sinking effects of multiple satellites, highlighting the importance of initial configuration and internal properties on orbital evolution.

Findings

Collective effects significantly alter satellite accretion histories.

Flat configurations cause larger deviations in orbital parameters.

Ignoring collective effects can lead to errors in merger history reconstruction.

Abstract

A variety of new physical processes have proven to play an important role in orbital decay of a satellite galaxy embedded inside a dark matter halo but this is not fully understood. Our goal is to assess if the orbital history of a satellite remains unchanged during a concurrent sinking. For this purpose we analyze the impact that the internal structure of the satellites and their spatial distribution inside the host halo may have on the concurrent sinking process due to both mass loss and the combined effect of self-friction, which have not been studied before for concurrent sinking. We set up a set of N-body simulations that include multiple satellites, sinking simultaneously in a host halo and we compare them with models including a single satellite. The main result of our work is that the satellite's accretion history differs from the classical isolated view when we consider the collective effects. The accretion history of each satellite strongly depends on the initial configuration, the number of satellites in the halo at the time of infall and the internal properties of each satellite. We observe that compact satellites in a flat configuration fall slower than extended satellites that have lost mass, showing a non-reported behavior of self-friction. We find that such effects are maximized when satellites are located in a flat configuration. We show that in a flat configuration similar to the Vast Polar Structure, deviations in the apocenters can be of about 30% with respect to the isolated case, and up to 50% on the eccentricities. We conclude that ignoring the collective effects produced by the concurrent sinking of satellite galaxies may lead to large errors in the determination of the merger progenitors properties, making it considerably more challenging to trace back the accretion event. Timing constrains on host density profile may be modified by the effects discussed here.