2025-01-15 アリゾナ大学
＜関連情報＞
- https://news.arizona.edu/news/ghost-towns-universe-ultra-faint-rare-dwarf-galaxies-offer-clues-early-cosmos
- https://iopscience.iop.org/article/10.3847/2041-8213/ad927c
NGC 300の方向にある3つのクエンチされた暗い矮小銀河：再電離と内部フィードバックの新たな研究対象 Three Quenched, Faint Dwarf Galaxies in the Direction of NGC 300: New Probes of Reionization and Internal Feedback
David J. Sand, Burçin Mutlu-Pakdil, Michael G. Jones, Ananthan Karunakaran, Jennifer E. Andrews, Paul Bennet, Denija Crnojević, Giuseppe Donatiello, Alex Drlica-Wagner, Catherine Fielder
The Astrophysical Journal Letters Published: 2024 December 2
DOI:10.3847/2041-8213/ad927c
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+0.10−0.13 Mpc; MV = −9.1 ± 0.1 mag or LV = (3.7+0.4−0.3) × 105L⊙) is consistent with being a satellite of NGC 300. Sculptor A (D = 1.35+0.22−0.08 Mpc; MV = −6.9 ± 0.3 mag or LV = (5+1−1) × 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+0.21−0.24 Mpc; MV = −8.1 ± 0.3 mag or LV = (1.5+0.5−0.4) × 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 rvir 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.
