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The first tidally disrupted ultra-faint dwarf galaxy?: a spectroscopic analysis of the Tucana III stream

The first tidally disrupted ultra-faint dwarf galaxy?: a spectroscopic analysis of the Tucana III stream
The first tidally disrupted ultra-faint dwarf galaxy?: a spectroscopic analysis of the Tucana III stream
We present a spectroscopic study of the tidal tails and core of the Milky Way satellite Tucana III, collectively referred to as the Tucana III stream, using the 2dF+AAOmega spectrograph on the Anglo-Australian Telescope and the IMACS spectrograph on the Magellan Baade Telescope. In addition to recovering the brightest nine previously known member stars in the Tucana III core, we identify 22 members in the tidal tails. We observe strong evidence for a velocity gradient of  over at least 3° on the sky. Based on the continuity in velocity, we confirm that the Tucana III tails are real tidal extensions of Tucana III. The large velocity gradient of the stream implies that Tucana III is likely on a radial orbit. We successfully obtain metallicities for four members in the core and 12 members in the tails. We find that members close to the ends of the stream tend to be more metal-poor than members in the core, indicating a possible metallicity gradient between the center of the progenitor halo and its edge. The spread in metallicity suggests that the progenitor of the Tucana III stream is likely a dwarf galaxy rather than a star cluster. Furthermore, we find that with the precise photometry of the Dark Energy Survey data, there is a discernible color offset between metal-rich disk stars and metal-poor stream members. This metallicity-dependent color offers a more efficient method to recognize metal-poor targets and will increase the selection efficiency of stream members for future spectroscopic follow-up programs on stellar streams.
0004-637X
Li, T.S.
7370e91b-a7a3-498f-83df-911efcdada99
Simon, J.D.
ff0fb67c-6b4a-40dc-8e53-32dfa94f1d3b
Kuehn, K.
c8275e43-4cd6-44f5-9cce-8475d0e5f7de
Smith, Mathew
8bdc74e1-a37b-434d-ae75-82763109bf7a
DES Collaboration
Li, T.S.
7370e91b-a7a3-498f-83df-911efcdada99
Simon, J.D.
ff0fb67c-6b4a-40dc-8e53-32dfa94f1d3b
Kuehn, K.
c8275e43-4cd6-44f5-9cce-8475d0e5f7de
Smith, Mathew
8bdc74e1-a37b-434d-ae75-82763109bf7a

Li, T.S., Simon, J.D., Kuehn, K. and Smith, Mathew , DES Collaboration (2018) The first tidally disrupted ultra-faint dwarf galaxy?: a spectroscopic analysis of the Tucana III stream. The Astrophysical Journal, 866 (1). (doi:10.3847/1538-4357/aadf91).

Record type: Article

Abstract

We present a spectroscopic study of the tidal tails and core of the Milky Way satellite Tucana III, collectively referred to as the Tucana III stream, using the 2dF+AAOmega spectrograph on the Anglo-Australian Telescope and the IMACS spectrograph on the Magellan Baade Telescope. In addition to recovering the brightest nine previously known member stars in the Tucana III core, we identify 22 members in the tidal tails. We observe strong evidence for a velocity gradient of  over at least 3° on the sky. Based on the continuity in velocity, we confirm that the Tucana III tails are real tidal extensions of Tucana III. The large velocity gradient of the stream implies that Tucana III is likely on a radial orbit. We successfully obtain metallicities for four members in the core and 12 members in the tails. We find that members close to the ends of the stream tend to be more metal-poor than members in the core, indicating a possible metallicity gradient between the center of the progenitor halo and its edge. The spread in metallicity suggests that the progenitor of the Tucana III stream is likely a dwarf galaxy rather than a star cluster. Furthermore, we find that with the precise photometry of the Dark Energy Survey data, there is a discernible color offset between metal-rich disk stars and metal-poor stream members. This metallicity-dependent color offers a more efficient method to recognize metal-poor targets and will increase the selection efficiency of stream members for future spectroscopic follow-up programs on stellar streams.

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More information

Accepted/In Press date: 3 September 2018
e-pub ahead of print date: 5 October 2018
Published date: 10 October 2018

Identifiers

Local EPrints ID: 427372
URI: https://eprints.soton.ac.uk/id/eprint/427372
ISSN: 0004-637X
PURE UUID: a7a689d3-6607-41e7-bfc1-6194df331c76
ORCID for Mathew Smith: ORCID iD orcid.org/0000-0002-3321-1432

Catalogue record

Date deposited: 14 Jan 2019 17:30
Last modified: 20 Jul 2019 00:36

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Contributors

Author: T.S. Li
Author: J.D. Simon
Author: K. Kuehn
Author: Mathew Smith ORCID iD

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