Three Quenched, Faint Dwarf Galaxies in the Direction of NGC 300: New Probes of Reionization and Internal Feedback

Understand

We report the discovery of three faint and ultra-faint dwarf galaxies -- Sculptor A, Sculptor B and Sculptor C -- in the direction of NGC 300 (D=2.0 Mpc), a Large Magellanic Cloud-mass galaxy.

• Deep ground-based imaging with Gemini/GMOS resolves all three dwarf galaxies into stars, each displaying a red giant branch indicative of an old, metal-poor stellar population.
• No young stars or HI gas are apparent, and the lack of a GALEX UV detection suggests that all three systems are quenched.
• Sculptor C (D=2.04$^{+0.10}_{-0.13}$ Mpc; $M_V$=$-$9.1$\pm$0.1 mag or $L_V$=(3.7$^{+0.4}_{-0.3}$)$\times$10$^5$ $L_{\odot}$) is consistent with being a satellite of NGC 300.