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Title: A Ghost in Boötes: The Least-Luminous Disrupted Dwarf Galaxy
Abstract We report the discovery of Specter, a disrupted ultrafaint dwarf galaxy revealed by the H3 Spectroscopic Survey. We detected this structure via a pair of comoving metal-poor stars at a distance of 12.5 kpc, and further characterized it with Gaia astrometry and follow-up spectroscopy. Specter is a 25° × 1° stream of stars that is entirely invisible until strict kinematic cuts are applied to remove the Galactic foreground. The spectroscopic members suggest a stellar age τ ≳ 12 Gyr and a mean metallicity 〈 [ Fe / H ] 〉 = − 1.84 − 0.18 + 0.16 , with a significant intrinsic metallicity dispersion σ [ Fe / H ] = 0.37 − 0.13 + 0.21 . We therefore argue that Specter is the disrupted remnant of an ancient dwarf galaxy. With an integrated luminosity M V ≈ −2.6, Specter is by far the least-luminous dwarf galaxy stream known. We estimate that dozens of similar streams are lurking below the detection threshold of current search techniques, and conclude that spectroscopic surveys offer a novel means to identify extremely low surface brightness structures.  more » « less
Award ID(s):
2107253
PAR ID:
10463511
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
940
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
127
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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