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

December 2024 • 2024ApJ...977L...5S

Authors • Sand, David J. • Mutlu-Pakdil, Burçin • Jones, Michael G. • Karunakaran, Ananthan • Andrews, Jennifer E. • Bennet, Paul • Crnojević, Denija • Donatiello, Giuseppe • Drlica-Wagner, Alex • Fielder, Catherine • Martínez-Delgado, David • Martínez-Vázquez, Clara E. • Spekkens, Kristine • Doliva-Dolinsky, Amandine • Hunter, Laura C. • Carlin, Jeffrey L. • Cerny, William • Hai, Tehreem N. • McQuinn, Kristen B. W. • Pace, Andrew B. • Smercina, Adam

Abstract • We report the discovery of three faint and ultrafaint 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 H I gas are apparent, and the lack of a GALEX UV detection suggests that all three systems are quenched. Sculptor C (D = 2.04 Mpc; M_V = −9.1 ± 0.1 mag or L_V = (3.7 ) × 10⁵L_⊙) is consistent with being a satellite of NGC 300. Sculptor A (D = 1.35 Mpc; M_V = −6.9 ± 0.3 mag or L_V = (5 ) × 10⁴L_⊙) is likely in the foreground of NGC 300 and at the extreme edge of the Local Group, analogous to the recently discovered ultrafaint Tucana B in terms of its physical properties and environment. Sculptor B (D = 2.48 Mpc; M_V = −8.1 ± 0.3 mag or L_V = (1.5 ) × 10⁵L_⊙) is likely in the background, but future distance measurements are necessary to solidify this statement. It is also of interest due to its quiescent state and low stellar mass. Both Sculptor A and B are ≳2─4 r_vir from NGC 300 itself. The discovery of three dwarf galaxies in isolated or low-density environments offers an opportunity to study the varying effects of ram-pressure stripping, reionization, and internal feedback in influencing the star formation history of the faintest stellar systems.

Links

• PREPRINT http://arxiv.org/abs/2409.16345
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2024ApJ...977L...5S
• ELECTR https://doi.org/10.3847/2041-8213/ad927c
• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2024ApJ...977L...5S
• PDF https://iopscience.iop.org/article/10.3847/2041-8213/ad927c/pdf
• DATA https://archive.gemini.edu/searchform/publication=2024ApJ...977L...5S