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A Ghost in Bo\'otes: The Least Luminous Disrupted Dwarf Galaxy

Authors :
Vedant Chandra
Charlie Conroy
Nelson Caldwell
Ana Bonaca
Rohan P. Naidu
Dennis Zaritsky
Phillip A. Cargile
Jiwon Jesse Han
Benjamin D. Johnson
Joshua S. Speagle
Yuan-Sen Ting
Turner Woody
Publication Year :
2022

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 $25^\circ \times 1^\circ$ 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 $\tau \gtrsim 12$ Gyr and a mean metallicity $\langle\text{[Fe/H]}\rangle = -1.84_{-0.18}^{+0.16}$, with a significant intrinsic metallicity dispersion $\sigma_{ \text{[Fe/H]}} = 0.37_{-0.13}^{+0.21}$. We therefore argue that Specter is the disrupted remnant of an ancient dwarf galaxy. With an integrated luminosity $M_{\text{V}} \approx -2.6$, 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.<br />Comment: 17 pages, 10 figures. Accepted to ApJ

Details

Language :
English
Database :
OpenAIRE
Accession number :
edsair.doi.dedup.....db1fc4b37b72105f65f27c90c4d6ad59