The Draco Dwarf Spheroidal Galaxy in the First Year of Dark Energy Spectroscopic Instrument Data
Abstract We investigate the spatial distribution, kinematics, and metallicity of stars in the Draco dwarf spheroidal galaxy using data from the Dark Energy Spectroscopic Instrument (DESI). We identify 155 high-probability members of Draco using line-of-sight velocity and metallicity information derived from DESI spectroscopy along with Gaia Data Release 3 proper motions. We find a mean line-of-sight velocity of −290.62 ± 0.80 km s −1 with dispersion = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>9.5</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.62</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.66</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> km s −1 and mean metallicity [Fe/H] = −2.10 ± 0.04, consistent with previous results. We also find that Draco has a steep metallicity gradient within the half-light radius, and a metallicity gradient that flattens beyond the half-light radius. We identify eight high-probability members outside the King tidal radius, four of which we identify for the first time. These extratidal stars are not preferentially aligned along the orbit of Draco. We compute an average surface brightness of 34.02 mag <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">arcsec</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> within an elliptical annulus from the King tidal radius of 48 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mi>.</mml:mi> <mml:mi>′</mml:mi> </mml:mover> </mml:math> 1–81′.
Authors
- Wenting Wang (ORCID: https://orcid.org/0000-0002-5762-7571)
- Mika Lambert (ORCID: https://orcid.org/0000-0002-2527-8899)
- O. Lahav (ORCID: https://orcid.org/0000-0002-1134-9035)
- 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)
- Graziano Rossi (ORCID: https://orcid.org/0000-0002-5102-5019)
- Gregory Tarlé (ORCID: https://orcid.org/0000-0003-1704-0781)
- Constance M. Rockosi (ORCID: https://orcid.org/0000-0002-6667-7028)
- 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)
- D. Bianchi (ORCID: https://orcid.org/0000-0001-9712-0006)
- Ignasi Pérez-Ràfols (ORCID: https://orcid.org/0000-0001-6979-0125)
- Axel de la Macorra (ORCID: https://orcid.org/0000-0002-1769-1640)
- Martin Landriau (ORCID: https://orcid.org/0000-0003-1838-8528)
- J. Aguilar (ORCID: https://orcid.org/0000-0003-0822-452X)
- Anthony Kremin (ORCID: https://orcid.org/0000-0001-6356-7424)
- J. Guy (ORCID: https://orcid.org/0000-0001-9822-6793)
- Eusebio Sanchez (ORCID: https://orcid.org/0000-0002-9646-8198)
- Satya Gontcho A Gontcho (ORCID: https://orcid.org/0000-0003-3142-233X)
- Jiani Ding (ORCID: https://orcid.org/0000-0003-4651-8510)
- Namitha Kizhuprakkat (ORCID: https://orcid.org/0000-0003-0853-8887)
- ENRIQUE GAZTAÑAGA (ORCID: https://orcid.org/0000-0001-9632-0815)
- Joseph Harry Silber (ORCID: https://orcid.org/0000-0002-3461-0320)
- B. A. Weaver
- Nathan R. Sandford (ORCID: https://orcid.org/0000-0002-7393-3595)
- G. Gutierrez (ORCID: https://orcid.org/0000-0003-0825-0517)
- 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)
- R. Miquel (ORCID: https://orcid.org/0000-0002-6610-4836)
- Theodore S. Kisner (ORCID: https://orcid.org/0000-0003-3510-7134)
- R. Kehoe (ORCID: https://orcid.org/0000-0002-7101-697X)
- John Moustakas (ORCID: https://orcid.org/0000-0002-2733-4559)
- Mustapha Ishak (ORCID: https://orcid.org/0000-0002-6024-466X)
- T. Claybaugh (ORCID: https://orcid.org/0000-0002-5024-6987)
- P. Doel (ORCID: https://orcid.org/0000-0002-6397-4457)
- M. Schubnell
- 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
- 2025-11-20
- DOI
- https://doi.org/10.3847/1538-4357/ae0a37
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- U.S. Department of Energy
- Gordon and Betty Moore Foundation
- Ministerio de Ciencia, Innovación y Universidades
- Ministry of Education, India
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives
- National Science and Technology Council
- Office of Science
- Natural Sciences and Engineering Research Council of Canada
- Science and Technology Facilities Council
- Agencia Estatal de Investigación
- Division of Astronomical Sciences
- High Energy Physics