MeerKAT and the Smallest Galaxies

TL;DR

This paper discusses how MeerKAT's sensitivity can help identify and analyze low-mass, HI-rich dwarf galaxies in the Centaurus region, addressing the small scale crisis in dark matter models.

Contribution

It proposes a comprehensive survey with MeerKAT to detect and characterize ultra-low mass dwarf galaxies, improving understanding of galaxy formation and dark matter halos.

Findings

Detection of galaxies with HI masses below 10^7 Msun is feasible.

The survey can identify objects similar to Leo T across the Centaurus region.

It will explore the extent of satellite planes around CenA.

Abstract

(Abridged) On small scales, there exists a tension between observations of dwarf galaxies and predictions for low-mass dark matter halos from simulations (often referred to as the small scale crisis). Detailed observations of low mass galaxies are critical for constraining the baryonic feedback processes that are used to alleviate these discrepancies. Dwarf galaxies with a substantial reservoir of neutral hydrogen (HI) are likely to be isolated, helping to disentangle intrinsic properties from evolutionary effects, and HI kinematics offer an immediate constraint on the hosting dark matter halo. Given MeerKAT's exquisite sensitivity, it can potentially contribute to these studies of low-mass HI-rich dwarf galaxies that will help resolve the small scale crisis. The current large HI surveys are not designed for these studies, but will still manage to detect a sample of galaxies with HI masses below 10^7 Msun comparable to the number of systems currently in the literature, and will resolve ~15 systems with masses below 10^8.5 Msun, a critical regime for addressing which dark matter halos host low-mass galaxies. We propose a thousand hour survey of the Centaurus region, encompassing the M83 and CenA galaxy groups, which can robustly address the central question: "How many galaxies equivalent to Leo T are there in the Centaurus region?" Leo T is the lowest mass, gas-rich galaxy currently known; our proposed survey is designed to be able to detect an object of similar HI mass and linewidth throughout the volume of the Centuaurus region, which will provide a full census of how many objects like this there are in a typical galaxy group. In addition, planes of satellites have recently been identified around CenA and our survey will be able to address how far out these planes extend: are they structures concentrated only around the central galaxy or are they connected to large scale structure?