$\Lambda$CDM Predictions for the Satellite Population of M33

TL;DR

This paper predicts the number and distribution of satellite galaxies around M33 using $ ext{Lambda}$CDM simulations, exploring how M33's orbital history influences its satellite population and how future surveys can test these predictions.

Contribution

It provides detailed $ ext{Lambda}$CDM-based predictions for M33's satellite population and assesses how orbital history affects satellite retention, guiding future observational strategies.

Findings

Predicted satellite count within 160 kpc of M33 based on simulations.

Survey of ~100 kpc around M33 can constrain its orbital history.

Satellite retention depends on M33's past tidal interactions.

Abstract

Triangulum (M33) is the most massive satellite galaxy of Andromeda (M31), with a stellar mass of about $3\times10^9\; M_{\odot}$. Based on abundance matching techniques, M33's total mass at infall is estimated to be of order $10^{11}\; M_{\odot}$. $\Lambda$CDM simulations predict that M33-mass halos host several of their own low mass satellite companions, yet only one candidate M33 satellite has been detected in deep photometric surveys to date. This `satellites of satellites' hierarchy has recently been explored in the context of the dwarf galaxies discovered around the Milky Way's Magellanic Clouds in the Dark Energy Survey. Here we discuss the number of satellite galaxies predicted to reside within the virial radius ($\sim$160 kpc) of M33 based on $\Lambda$CDM simulations. We also calculate the expected number of satellite detections in N fields of data using various ground--based imagers. Finally, we discuss how these satellite population predictions change as a function of M33's past orbital history. If M33 is on its first infall into M31's halo, its proposed satellites are expected to remain bound to M33 today. However, if M33 experienced a recent tidal interaction with M31, the number of surviving satellites depends strongly on the distance achieved at pericenter due to the effects of tidal stripping. We conclude that a survey extending to $\sim$100 kpc around M33 would be sufficient to constrain its orbital history and a majority of its satellite population. In the era of WFIRST, surveys of this size will be considered small observing programs.