Abstract
We report the discovery of Tucana B, an isolated ultra-faint dwarf galaxy at a distance of D = 1.4 Mpc. Tucana B was found during a search for ultra-faint satellite companions to the known dwarfs in the outskirts of the Local Group, although its sky position and distance indicate the nearest galaxy to be ∼500 kpc distant. Deep ground-based imaging resolves Tucana B into stars, and it displays a sparse red giant branch consistent with an old, metal-poor stellar population analogous to that seen in the ultra-faint dwarf galaxies of the Milky Way, albeit at fainter apparent magnitudes. Tucana B has a half-light radius of 80 ± 40 pc and an absolute magnitude of M V = − 6.9 − 0.6 + 0.5 mag ( L V = ( 5 − 2 + 4 ) × 10 4 L ⊙), which is again comparable to the Milky Way’s ultra-faint satellites. There is no evidence for a population of young stars, either in the optical color-magnitude diagram or in GALEX archival ultraviolet imaging, with the GALEX data indicating log ( SFR NUV / M ⊙ yr − 1 ) < − 5.4 for star formation on ≲100 Myr timescales. Given its isolation and physical properties, Tucana B may be a definitive example of an ultra-faint dwarf that has been quenched by reionization, providing strong confirmation of a key driver of galaxy formation and evolution at the lowest mass scales. It also signals a new era of ultra-faint dwarf galaxy discovery at the extreme edges of the Local Group.
Original language | English (US) |
---|---|
Article number | L17 |
Journal | Astrophysical Journal Letters |
Volume | 935 |
Issue number | 1 |
DOIs | |
State | Published - Aug 1 2022 |
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
Fingerprint
Dive into the research topics of 'Tucana B: A Potentially Isolated and Quenched Ultra-faint Dwarf Galaxy at D ≈ 1.4 Mpc* * This paper includes data gathered with the 6.5 m Magellan Telescope at Las Campanas Observatory, Chile.'. Together they form a unique fingerprint.Datasets
-
Magellan IMACS color-magnitude diagram for Tucana B
Sand, D. J. (Creator), Mutlu-Pakdil, B. (Creator), Jones, M. G. (Creator), Karunakaran, A. (Creator), Wang, F. (Creator), Yang, J. (Creator), Chiti, A. (Creator), Bennet, P. (Creator), Crnojević, D. (Contributor) & Spekkens, K. (Creator), Centre de Donnees Strasbourg (CDS), 2024
DOI: 10.26093/cds/vizier.19359017, https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/935/L17
Dataset