# Gas-rich dwarf galaxies as a new probe of dark matter interactions with ordinary matter

## TL;DR

This paper uses gas-rich dwarf galaxy observations to set new constraints on dark matter interactions with ordinary matter, surpassing previous limits across a wide mass range and providing insights into dark matter properties at low velocities.

## Contribution

It introduces a novel method of constraining dark matter interactions using gas-rich dwarf galaxies, improving bounds on ultra-light hidden photons, millicharged dark matter, and low-velocity baryon interactions.

## Key findings

- Stronger bounds on ultra-light hidden photon dark matter across a broad mass range.
- Additional constraints on sub-GeV millicharged dark matter related to the EDGES 21cm anomaly.
- Limits on dark matter-baryon interactions at low relative velocities.

## Abstract

We use observations of gas-rich dwarf galaxies to derive constraints on dark matter scattering with ordinary matter. We require that heating/cooling due to DM interacting with gas in the Leo T dwarf galaxy not exceed the ultra-low radiative cooling rate of the gas. This enables us to set $(i)$ stronger bounds than all the previous literature on ultra-light hidden photon DM for nearly all of the mass range $10^{-23}\lesssim m_\mathrm{DM} \lesssim 10^{-10}$ eV, $(ii)$ limits on sub-GeV millicharged DM which add to the constraints on the recent EDGES 21cm absorption anomaly, and $(iii)$ constraints on DM-baryon interactions directly at low relative velocities $v_\mathrm{rel}\sim 17$ km/s. Our study opens a new direction at using observations of gas-rich dwarf galaxies from previous, current and upcoming optical and 21cm surveys to probe physics beyond the standard model.