GD-1 Stellar Stream and Cocoon in the DESI Early Data Release
Abstract We present ∼115 new spectroscopically identified members of the GD-1 tidal stream observed with the 5000-fiber Dark Energy Spectroscopic Instrument (DESI). We confirm the existence of a “cocoon,” which is a broad (FWHM ∼ 2 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 932 ∼ 460 pc) and kinematically hot (velocity dispersion, σ ∼ 5–8 km s −1 ) component that surrounds a narrower (FWHM ∼ 0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 353 ∼ 55 pc) and colder [( σ = 3.09 ± 0.76 km s −1 )] thin stream component (based on a median per star velocity precision of 2.7 km s −1 ). The cocoon extends over at least a 30 ∘ segment of the stream observed by DESI. The thin and cocoon components have similar mean values of [Fe/H]: −2.54 ± 0.04 dex and −2.47 ± 0.06 dex, suggestive of a common origin. The data are consistent with the following scenarios for the origin of the cocoon. The progenitor of the GD-1 stream was an accreted globular cluster (GC) and: (a) the cocoon was produced by pre-accretion tidal stripping of the GC while it was still inside its parent dwarf galaxy; (b) the cocoon comprises debris from the parent dwarf galaxy; (c) an initially thin GC tidal stream was heated by impacts from dark subhalos in the Milky Way; (d) an initially thin GC stream was heated by a massive Sagittarius dwarf galaxy; or a combination of some of these. Future DESI spectroscopy and detailed modeling may enable us to distinguish between these possible origins.
Authors
- Andrew Lambert (ORCID: https://orcid.org/0009-0003-5658-2601)
- D. Brooks (ORCID: https://orcid.org/0000-0002-8458-5047)
- Rongpu Zhou (ORCID: https://orcid.org/0000-0001-5381-4372)
- G. E. Medina (ORCID: https://orcid.org/0000-0003-0105-9576)
- Ting S. Li (ORCID: https://orcid.org/0000-0002-9110-6163)
- R. Miquel
- J. Ereza (ORCID: https://orcid.org/0000-0002-0194-4017)
- Gregory Tarlé (ORCID: https://orcid.org/0000-0003-1704-0781)
- Laurent Le Guillou (ORCID: https://orcid.org/0000-0001-7178-8868)
- David Sprayberry (ORCID: https://orcid.org/0000-0001-7583-6441)
- Alexander H. Riley (ORCID: https://orcid.org/0000-0001-5805-5766)
- David J. Schlegel (ORCID: https://orcid.org/0000-0002-5042-5088)
- Axel de la Macorra (ORCID: https://orcid.org/0000-0002-1769-1640)
- Parker Fagrelius (ORCID: https://orcid.org/0000-0001-6974-5826)
- Martin Landriau (ORCID: https://orcid.org/0000-0003-1838-8528)
- M. E. Levi (ORCID: https://orcid.org/0000-0003-1887-1018)
- Eric F. Bell (ORCID: https://orcid.org/0000-0002-5564-9873)
- Marc Manera (ORCID: https://orcid.org/0000-0003-4962-8934)
- J. Aguilar (ORCID: https://orcid.org/0000-0003-0822-452X)
- Anthony Kremin (ORCID: https://orcid.org/0000-0001-6356-7424)
- Eusebio Sanchez (ORCID: https://orcid.org/0000-0002-9646-8198)
- Satya Gontcho A Gontcho (ORCID: https://orcid.org/0000-0003-3142-233X)
- Oleg Y. Gnedin (ORCID: https://orcid.org/0000-0001-9852-9954)
- ENRIQUE GAZTAÑAGA (ORCID: https://orcid.org/0000-0001-9632-0815)
- R. G. Carlberg (ORCID: https://orcid.org/0000-0002-7667-0081)
- Vasily Belokurov (ORCID: https://orcid.org/0000-0002-0038-9584)
- Arjun T. Dey (ORCID: https://orcid.org/0000-0002-4928-4003)
- Joan Najita (ORCID: https://orcid.org/0000-0002-5758-150X)
- J. E. Forero-Romero (ORCID: https://orcid.org/0000-0002-2890-3725)
- Steven P. Ahlen (ORCID: https://orcid.org/0000-0001-6098-7247)
- Andrew P. Cooper (ORCID: https://orcid.org/0000-0001-8274-158X)
- Aaron Meisner (ORCID: https://orcid.org/0000-0002-1125-7384)
- Sergey E. Koposov (ORCID: https://orcid.org/0000-0003-2644-135X)
- Guillaume F. Thomas (ORCID: https://orcid.org/0000-0002-2468-5521)
- K. Dawson
- K. Honscheid
- Theodore S. Kisner (ORCID: https://orcid.org/0000-0003-3510-7134)
- Mehdi Rezaie (ORCID: https://orcid.org/0000-0001-5589-7116)
- Risa H. Wechsler (ORCID: https://orcid.org/0000-0003-2229-011X)
- John Moustakas (ORCID: https://orcid.org/0000-0002-2733-4559)
- Leandro José Beraldo e Silva (ORCID: https://orcid.org/0000-0002-0740-1507)
- Claire Poppett (ORCID: https://orcid.org/0000-0003-0512-5489)
- Amanda Byström (ORCID: https://orcid.org/0000-0002-5689-8791)
- Monica Valluri (ORCID: https://orcid.org/0000-0002-6257-2341)
- J. Han (ORCID: https://orcid.org/0000-0002-6800-5778)
- Carlos Allende Prieto (ORCID: https://orcid.org/0000-0002-0084-572X)
- Hu Zou (ORCID: https://orcid.org/0000-0002-6684-3997)
- P. Doel
- B. A. Weaver
- M. Schubnell
- T. Claybaugh
- Adam D. Myers
- F. Prada (ORCID: https://orcid.org/0000-0001-7145-8674)
Institutions
- Laboratoire de Physique Nucléaire et de Hautes Énergies (FR)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-02-05
- DOI
- https://doi.org/10.3847/1538-4357/ada690
- Citations
- 11
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 12.70
Funders
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Alfred P. Sloan Foundation
- Gordon and Betty Moore Foundation
- California Institute of Technology
- European Space Agency
- Chinese Academy of Sciences
- Consejo Nacional de Ciencia y Tecnología
- Nuclear Safety and Security Commission
- Ministerio de Ciencia e Innovación
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives
- National Science and Technology Council
- Office of Science
- Jet Propulsion Laboratory
- Natural Sciences and Engineering Research Council of Canada
- Science and Technology Facilities Council
- Division of Astronomical Sciences
- High Energy Physics
- Lawrence Berkeley National Laboratory