Three Quenched, Faint Dwarf Galaxies in the Direction of NGC 300: New Probes of Reionization and Internal Feedback
D. J. Sand, B. Mutlu-Pakdil, M. G. Jones, A. Karunakaran, J. E. Andrews, P. Bennet, D. Crnojevic, G. Donatiello, A. Drlica-Wagner, C. Fielder, D. Martinez-Delgado, C. E. Martinez-Vazquez, K. Spekkens, A. Doliva-Dolinsky, L. C. Hunger, J. L. Carlin, W. Cerny, T. N. Hai, K. B. W McQuinn, A. B. Pace, A. Smercina
arXiv:2409.16345v1 Announce Type: new
Abstract: 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. Sculptor A (D=1.35$^{+0.22}_{-0.08}$ Mpc; $M_V$=$-$6.9$pm$0.3 mag or $L_V$=(5$^{+1}_{-1}$)$times$10$^4$ $L_{odot}$) is likely in the foreground of NGC 300 and at the extreme edge of the Local Group, analogous to the recently discovered ultra-faint Tucana B in terms of its physical properties and environment. Sculptor B (D=2.48$^{+0.21}_{-0.24}$ Mpc; $M_V$=$-$8.1$pm$0.3 mag or $L_V$=(1.5$^{+0.5}_{-0.4}$)$times$10$^5$ $L_{odot}$) 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 $gtrsim$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.arXiv:2409.16345v1 Announce Type: new
Abstract: 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. Sculptor A (D=1.35$^{+0.22}_{-0.08}$ Mpc; $M_V$=$-$6.9$pm$0.3 mag or $L_V$=(5$^{+1}_{-1}$)$times$10$^4$ $L_{odot}$) is likely in the foreground of NGC 300 and at the extreme edge of the Local Group, analogous to the recently discovered ultra-faint Tucana B in terms of its physical properties and environment. Sculptor B (D=2.48$^{+0.21}_{-0.24}$ Mpc; $M_V$=$-$8.1$pm$0.3 mag or $L_V$=(1.5$^{+0.5}_{-0.4}$)$times$10$^5$ $L_{odot}$) 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 $gtrsim$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.