A Ghost in Boötes: The Least-Luminous Disrupted Dwarf Galaxy

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

doi:10.3847/1538-4357/ac9b4b

A Ghost in Boötes: The Least-Luminous Disrupted Dwarf Galaxy

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

Astronomy

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

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.

Original language	English (US)
Article number	127
Journal	Astrophysical Journal
Volume	940
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/ac9b4b
State	Published - Dec 1 2022

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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@article{adba442381ba4c269a4bc82a866a0b1d,

title = "A Ghost in Bo{\"o}tes: 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.",

author = "Vedant Chandra and Charlie Conroy and Nelson Caldwell and Ana Bonaca and Naidu, {Rohan P.} and Dennis Zaritsky and Cargile, {Phillip A.} and Han, {Jiwon Jesse} and Johnson, {Benjamin D.} and Speagle, {Joshua S.} and Ting, {Yuan Sen} and Turner Woody",

note = "Publisher Copyright: {\textcopyright} 2022. The Author(s). Published by the American Astronomical Society.",

year = "2022",

month = dec,

day = "1",

doi = "10.3847/1538-4357/ac9b4b",

language = "English (US)",

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journal = "Astrophysical Journal",

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TY - JOUR

T1 - A Ghost in Boötes

T2 - The Least-Luminous Disrupted Dwarf Galaxy

AU - Chandra, Vedant

AU - Conroy, Charlie

AU - Caldwell, Nelson

AU - Bonaca, Ana

AU - Naidu, Rohan P.

AU - Zaritsky, Dennis

AU - Cargile, Phillip A.

AU - Han, Jiwon Jesse

AU - Johnson, Benjamin D.

AU - Speagle, Joshua S.

AU - Ting, Yuan Sen

AU - Woody, Turner

PY - 2022/12/1

Y1 - 2022/12/1

N2 - 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.

AB - 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.

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A Ghost in Boötes: The Least-Luminous Disrupted Dwarf Galaxy

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