An observer's guide to the (Local Group) dwarf galaxies: predictions for their own dwarf satellite populations

TL;DR

This paper predicts the number of faint dwarf satellite galaxies around Local Group field dwarfs using simulations and models, guiding future observational searches and refining galaxy formation theories.

Contribution

It provides quantitative predictions for satellite populations around field dwarf galaxies, incorporating multiple models and highlighting observational strategies.

Findings

High probability (>99%) of satellites >10^5 M_sun around large field dwarfs.

Predicted 5-25 satellites >10^4 M_sun for the five largest field dwarfs.

Large survey areas are needed due to small numbers and extended distribution of satellites.

Abstract

A recent surge in the discovery of new ultrafaint dwarf satellites of the Milky Way has inspired the idea of searching for faint satellites, $10^3\, \mathrm{M_{\odot}} < M_* < 10^6\, \mathrm{M_{\odot}}$, around less massive field galaxies in the Local Group. Such satellites would be subject to weaker environmental influences than Milky Way satellites, and could lead to new insights on low mass galaxy formation. In this paper, we predict the number of luminous satellites expected around field dwarf galaxies by applying several abundance matching models and a reionization model to the dark-matter only \textit{Caterpillar} simulation suite. For three of the four abundance matching models used, we find a $>99\%$ chance that at least one satellite with stellar mass $M_*> 10^5\, \mathrm{M_{\odot}}$ exists around the combined five Local Group field dwarf galaxies with the largest stellar mass. When considering satellites with $M_*> 10^4\, \mathrm{M_{\odot}}$, we predict a combined $5-25$ satellites for the five largest field dwarfs, and $10-50$ for the whole Local Group field dwarf population. Because of the relatively small number of predicted dwarfs, and their extended spatial distribution, a large fraction each Local Group dwarf's virial volume will need to be surveyed to guarantee discoveries. We compute the predicted number of satellites in a given field of view of specific Local Group galaxies, as a function of minimum satellite luminosity, and explicitly obtain such values for the Solitary Local dwarfs survey. Uncertainties in abundance matching and reionization models are large, implying that comprehensive searches could lead to refinements of both models.