The Draco Dwarf Spheroidal Galaxy in the First Year of DESI Data

J. Ding; C. Rockosi; Ting S. Li; S. E.  Koposov; A. H. Riley; W. Wang; A. P. Cooper; N. Kizhuprakkat; M Lambert; G. E. Medina; N. Sandford; J. Aguilar; S. Ahlen; D. Bianchi; D Brooks; T. Claybaugh; A. de la Macorra; P. Doel; J. E. Forero-Romero; E. Gaztañaga; S. Gontcho A Gontcho; G. Gutierrez; J. Guy; M. Ishak; R. Kehoe; T. Kisner; A. Kremin; O. Lahav; M. Landriau; L. Le Guillou; A. Meisner; R. Miquel; J. Moustakas; F. Prada; I. Pérez-Ràfols; G. Rossi; E. Sanchez; M Schubnell; J. Silberg; D. Sprayberry; G. Tarle; B.A.  Weaver; R. Zhou

doi:10.3847/1538-4357/ae0a37

The Draco Dwarf Spheroidal Galaxy in the First Year of DESI Data

J. Ding
, C. Rockosi
, Ting S. Li
, S. E. Koposov
, A. H. Riley
, W. Wang
, A. P. Cooper
, N. Kizhuprakkat
, M Lambert
, G. E. Medina
, N. Sandford
, J. Aguilar
, S. Ahlen
, D. Bianchi
, D Brooks
, T. Claybaugh
, A. de la Macorra
, P. Doel
, J. E. Forero-Romero
, E. Gaztañaga

S. Gontcho A Gontcho, G. Gutierrez, J. Guy, M. Ishak, R. Kehoe, T. Kisner, A. Kremin, O. Lahav, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, M Schubnell, J. Silberg, D. Sprayberry, G. Tarle, B.A. Weaver, R. Zhou

School of Physics and Astronomy

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

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 DR3 proper motions. We find a mean line of sight velocity of −290.62±0.80 km s−1 with dispersion = 9.57+0.66−0.62 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 extra-tidal stars are not preferentially aligned along the orbit of Draco. We compute an average
surface brightness of 34.02 mag arcsec−2 within an elliptical annulus from the King tidal radius of 48.1 arcmin to 81 arcmin.

Original language	English
Article number	134
Pages (from-to)	1-13
Number of pages	13
Journal	Astrophysical Journal
Volume	994
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/ae0a37
Publication status	Published - 20 Nov 2025

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10.3847/1538-4357/ae0a37Licence: Creative Commons: Attribution (CC-BY)

Draco_Mixture_Project_aas_submission_arxivAccepted author manuscript, 1.2 MBLicence: Creative Commons: Attribution (CC-BY)

Probing dark matter distribution in the Milky Way with the DESI survey
Koposov, S. (Principal Investigator) & Penarrubia, J. (Co-investigator)
Science and Technology Facilities Council
1/04/24 → 31/03/28
Project: Research

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Ding, J., Rockosi, C., Li, T. S., Koposov, S. E., Riley, A. H., Wang, W., Cooper, A. P., Kizhuprakkat, N., Lambert, M., Medina, G. E., Sandford, N., Aguilar, J., Ahlen, S., Bianchi, D., Brooks, D., Claybaugh, T., de la Macorra, A., Doel, P., Forero-Romero, J. E., ... Zhou, R. (2025). The Draco Dwarf Spheroidal Galaxy in the First Year of DESI Data. Astrophysical Journal, 994(1), 1-13. Article 134. https://doi.org/10.3847/1538-4357/ae0a37

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title = "The Draco Dwarf Spheroidal Galaxy in the First Year of DESI 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 DR3 proper motions. We find a mean line of sight velocity of −290.62±0.80 km s−1 with dispersion = 9.57+0.66−0.62 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 extra-tidal stars are not preferentially aligned along the orbit of Draco. We compute an average surface brightness of 34.02 mag arcsec−2 within an elliptical annulus from the King tidal radius of 48.1 arcmin to 81 arcmin.",

author = "J. Ding and C. Rockosi and Li, \{Ting S.\} and Koposov, \{S. E.\} and Riley, \{A. H.\} and W. Wang and Cooper, \{A. P.\} and N. Kizhuprakkat and M Lambert and Medina, \{G. E.\} and N. Sandford and J. Aguilar and S. Ahlen and D. Bianchi and D Brooks and T. Claybaugh and \{de la Macorra\}, A. and P. Doel and Forero-Romero, \{J. E.\} and E. Gazta{\~n}aga and \{Gontcho A Gontcho\}, S. and G. Gutierrez and J. Guy and M. Ishak and R. Kehoe and T. Kisner and A. Kremin and O. Lahav and M. Landriau and Guillou, \{L. Le\} and A. Meisner and R. Miquel and J. Moustakas and F. Prada and I. P{\'e}rez-R{\`a}fols and G. Rossi and E. Sanchez and M Schubnell and J. Silberg and D. Sprayberry and G. Tarle and B.A. Weaver and R. Zhou",

year = "2025",

month = nov,

day = "20",

doi = "10.3847/1538-4357/ae0a37",

language = "English",

volume = "994",

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journal = "Astrophysical Journal",

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publisher = "American Astronomical Society",

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Ding, J, Rockosi, C, Li, TS, Koposov, SE, Riley, AH, Wang, W, Cooper, AP, Kizhuprakkat, N, Lambert, M, Medina, GE, Sandford, N, Aguilar, J, Ahlen, S, Bianchi, D, Brooks, D, Claybaugh, T, de la Macorra, A, Doel, P, Forero-Romero, JE, Gaztañaga, E, Gontcho A Gontcho, S, Gutierrez, G, Guy, J, Ishak, M, Kehoe, R, Kisner, T, Kremin, A, Lahav, O, Landriau, M, Guillou, LL, Meisner, A, Miquel, R, Moustakas, J, Prada, F, Pérez-Ràfols, I, Rossi, G, Sanchez, E, Schubnell, M, Silberg, J, Sprayberry, D, Tarle, G, Weaver, BA & Zhou, R 2025, 'The Draco Dwarf Spheroidal Galaxy in the First Year of DESI Data', Astrophysical Journal, vol. 994, no. 1, 134, pp. 1-13. https://doi.org/10.3847/1538-4357/ae0a37

TY - JOUR

T1 - The Draco Dwarf Spheroidal Galaxy in the First Year of DESI Data

AU - Ding, J.

AU - Rockosi, C.

AU - Li, Ting S.

AU - Koposov, S. E.

AU - Riley, A. H.

AU - Wang, W.

AU - Cooper, A. P.

AU - Kizhuprakkat, N.

AU - Lambert, M

AU - Medina, G. E.

AU - Sandford, N.

AU - Aguilar, J.

AU - Ahlen, S.

AU - Bianchi, D.

AU - Brooks, D

AU - Claybaugh, T.

AU - de la Macorra, A.

AU - Doel, P.

AU - Forero-Romero, J. E.

AU - Gaztañaga, E.

AU - Gontcho A Gontcho, S.

AU - Gutierrez, G.

AU - Guy, J.

AU - Ishak, M.

AU - Kehoe, R.

AU - Kisner, T.

AU - Kremin, A.

AU - Lahav, O.

AU - Landriau, M.

AU - Guillou, L. Le

AU - Meisner, A.

AU - Miquel, R.

AU - Moustakas, J.

AU - Prada, F.

AU - Pérez-Ràfols, I.

AU - Rossi, G.

AU - Sanchez, E.

AU - Schubnell, M

AU - Silberg, J.

AU - Sprayberry, D.

AU - Tarle, G.

AU - Weaver, B.A.

AU - Zhou, R.

PY - 2025/11/20

Y1 - 2025/11/20

N2 - 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 DR3 proper motions. We find a mean line of sight velocity of −290.62±0.80 km s−1 with dispersion = 9.57+0.66−0.62 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 extra-tidal stars are not preferentially aligned along the orbit of Draco. We compute an average surface brightness of 34.02 mag arcsec−2 within an elliptical annulus from the King tidal radius of 48.1 arcmin to 81 arcmin.

AB - 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 DR3 proper motions. We find a mean line of sight velocity of −290.62±0.80 km s−1 with dispersion = 9.57+0.66−0.62 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 extra-tidal stars are not preferentially aligned along the orbit of Draco. We compute an average surface brightness of 34.02 mag arcsec−2 within an elliptical annulus from the King tidal radius of 48.1 arcmin to 81 arcmin.

U2 - 10.3847/1538-4357/ae0a37

DO - 10.3847/1538-4357/ae0a37

M3 - Article

SN - 0004-637X

VL - 994

SP - 1

EP - 13

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 134

ER -

The Draco Dwarf Spheroidal Galaxy in the First Year of DESI Data

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Probing dark matter distribution in the Milky Way with the DESI survey

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