Ultra-Faint Milky Way Satellites Discovered in Carina, Phoenix, and Telescopium with DELVE Data Release 3

Journal Article · Mon Oct 13 04:00:00 EDT 2025 · No journal information

OSTI ID:2998959

Tan, Chin Yi ^[1]; Cerny, W. ^[2]; Pace, A. B. ^[3]; Sharp, J. A. ^[4]; Overdeck, K. ^[5]; Drlica-Wagner, A. ^[6]; Simon, J. D. ^[7]; Mutlu-Pakdil, B. ^[8]; Sand, D. J. ^[9]; Senkevich, A. M. ^[10]; Erkal, D. ^[10]; Ferguson, P. S. ^[11]; Sobreira, F. ^[12]; Atzberger, K. R. ^[3]; Carlin, J. L. ^[13]; Chiti, A. ^[4]; Crnojević, D. ^[14]; Ji, A. P. ^[4]; Johnson, L. C. ^[15]; Li, T. S. ^[16] ; Limberg, G. ^[4]; Martínez-Vázquez, C. E. ^[17]; Medina, G. E. ^[16]; Placco, V. M. ^[18]; Riley, A. H. ^[19]; Tollerud, E. J. ^[20]; Vivas, A. K. ^[21]; Abbott, T. M.C. ^[21]; Aguena, M. ^[22]; Alves, O. ^[23]; Bacon, D. ^[24]; Bocquet, S. ^[25]; Brooks, D. ^[26]; Burke, D. L. ^[27]; Camilleri, R. ^[28]; Carballo-Bello, J. A. ^[29]; Carnero Rosell, A. ^[30]; Carretero, J. ^[31]; Cheng, Ting-Yun ^[32]; Choi, Y. ^[18]; da Costa, L. N. ^[33]; da Silva Pereira, M. E. ^[34]; Davis, T. M. ^[28]; De Vicente, J. ^[35]; Desai, S. ^[36]; Doel, P. ^[26]; Everett, S. ^[37]; Flaugher, B. ^[38]; Frieman, J. ^[39]; García-Bellido, J. ^[40]; Gruen, D. ^[25]; Gutierrez, G. ^[38]; Hinton, S. R. ^[28]; Hollowood, D. L. ^[41]; James, D. J. ^[42]; Kuehn, K. ^[43]; Lee, S. ^[44]; Marshall, J. L. ^[45]; Mena-Fernández, J. ^[46]; Menanteau, F. ^[47]; Miquel, R. ^[48]; Myles, J. ^[49]; Navabi, M. ^[10]; Nidever, D. L. ^[50]; Ogando, Ricardo ^[51]; Plazas Malagón, A. A. ^[27]; Porredon, A. ^[52]; Samuroff, S. ^[53]; Sanchez, E. ^[35]; Sanchez Cid, D. ^[54]; Sevilla-Noarbe, I. ^[35]; Smith, M. ^[55]; Suchyta, E. ^[56]; Swanson, M. E.C. ^[57]; Vikram, V. ^[58]; Walker, Alistair ^[21]; Zenteno, A. ^[21]

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1. Chicago U., Astron. Astrophys. Ctr.; Chicago U., EFI; Chicago U., KICP; Chicago U.; SkAI, Chicago
2. Yale U., Math. Dept.
3. Virginia U., Astron. Dept.
4. Chicago U., Astron. Astrophys. Ctr.; Chicago U., EFI; Chicago U., KICP
5. Chicago U., Astron. Astrophys. Ctr.; Chicago U., EFI; Chicago U., KICP; SkAI, Chicago
6. Fermilab; Chicago U., Astron. Astrophys. Ctr.; Chicago U., EFI; Chicago U., KICP; SkAI, Chicago
7. Carnegie Inst. Observ.
8. Dartmouth Coll.
9. Arizona U., Astron. Dept. - Steward Observ.
10. Surrey U.
11. Washington U., Seattle
12. LIneA, Rio de Janeiro; Campinas State U.
13. NOAO, Tucson
14. South Florida U.
15. Northwestern U. (main)
16. Toronto U., Astron. Dept.
17. Gemini Observ., Hilo
18. Natl. Solar Observ., Tucson
19. Lund U.; Durham U., ICC
20. Baltimore, Space Telescope Sci.
21. Cerro-Tololo InterAmerican Obs.
22. Trieste Observ.; LIneA, Rio de Janeiro
23. U. Michigan, Ann Arbor
24. Portsmouth U., ICG
25. Munich U., ASC
26. University Coll. London
27. KIPAC, Menlo Park; SLAC
28. Queensland U.
29. Tarapaca U.
30. IAC, La Laguna; LIneA, Rio de Janeiro; Laguna U., Tenerife
31. Barcelona, IFAE
32. Groningen U.
33. LIneA, Rio de Janeiro
34. Hamburg Observ.
35. Madrid, CIEMAT; Madrid, Escuela Tec. Sup. Ing. Ind.
36. Indian Inst. Tech., Hyderabad
37. Caltech
38. Fermilab
39. Chicago U., Astron. Astrophys. Ctr.; Fermilab; Chicago U., EFI; Chicago U., KICP
40. Madrid, IFT
41. UC, Santa Cruz
42. Harvard-Smithsonian Ctr. Astrophys.
43. Australian Astron. Observ.; Lowell Observ.
44. Caltech, JPL
45. Texas A-M
46. LPSC, Grenoble
47. Illinois U., Urbana (main); Illinois U., Urbana, Astron. Dept.
48. ICREA, Barcelona; Barcelona, IFAE
49. Princeton U., Astrophys. Sci. Dept.
50. Montana State U.
51. Campinas State U.; Rio de Janeiro Observ.
52. Madrid, CIEMAT; Madrid, Escuela Tec. Sup. Ing. Ind.; Ruhr U., Bochum
53. Northeastern U.; Barcelona, IFAE
54. Madrid, CIEMAT; Madrid, Escuela Tec. Sup. Ing. Ind.; Zurich U.
55. Lancaster U.
56. ORNL, Oak Ridge (main)
57. Illinois U., Urbana (main)
58. Calicut U.

We report the discovery of three Milky Way satellite candidates: Carina IV, Phoenix III, and DELVE 7, in the third data release of the DECam Local Volume Exploration survey (DELVE). The candidate systems were identified by cross-matching results from two independent search algorithms. All three are extremely faint systems composed of old, metal-poor stellar populations ($$τ\gtrsim 10$$ Gyr, [Fe/H] $$ \lesssim -1.4$$). Carina IV ($$M_V = -2.8;\ r_{1/2} = 40 {\rm pc}$$) and Phoenix III ($$M_V = -1.2;\ r_{1/2} = 19 {\rm pc}$$) have half-light radii that are consistent with the known population of dwarf galaxies, while DELVE 7 ($$M_V = 1.2;\ r_{1/2} = 2 {\rm pc}$$) is very compact and seems more likely to be a star cluster, though its nature remains ambiguous without spectroscopic followup. The Gaia proper motions of stars in Carina IV ($$M_* = 2250^{+1180}_{-830} {\rm M_\odot}$$) indicate that it is unlikely to be associated with the LMC, while DECam CaHK photometry confirms that its member stars are metal-poor. Phoenix III ($$M_* = 520^{+660}_{-290} {\rm M_\odot}$$) is the faintest known satellite in the extreme outer stellar halo ($$D_{\rm GC} > 100$$ kpc), while DELVE 7 ($$M_* = 60^{+120}_{-40} {\rm M_\odot}$$) is the faintest known satellite with $$D_{\rm GC} > 20$$ kpc.

• Research Organization: Rio de Janeiro Observ.; IAC, La Laguna; Indian Inst. Tech., Hyderabad; Gemini Observ., Hilo; Northwestern U. (main); Chicago U.; LPSC, Grenoble; Chicago U., Astron. Astrophys. Ctr.; Toronto U., Astron. Dept.; Baltimore, Space Telescope Sci.; Madrid, Escuela Tec. Sup. Ing. Ind.; Northeastern U.; Zurich U.; Chicago U., EFI; UC, Santa Cruz; Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); NOAO, Tucson; Cerro-Tololo InterAmerican Obs.; Groningen U.; Lancaster U.; Surrey U.; Madrid, CIEMAT; Campinas State U.; Chicago U., KICP; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); SkAI, Chicago; Harvard-Smithsonian Ctr. Astrophys.; Arizona U., Astron. Dept. - Steward Observ.; Tarapaca U.; Natl. Solar Observ., Tucson; Laguna U., Tenerife; Ruhr U., Bochum; Montana State U.; Yale U., Math. Dept.; Illinois U., Urbana (main); Virginia U., Astron. Dept.; University Coll. London; Illinois U., Urbana, Astron. Dept.; Hamburg Observ.; U. Michigan, Ann Arbor; Madrid, IFT; South Florida U.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Munich U., ASC; Dartmouth Coll.; Queensland U.; Caltech; Lowell Observ.; Durham U., ICC; Caltech, JPL; Texas A-M; Princeton U., Astrophys. Sci. Dept.; Australian Astron. Observ.; ICREA, Barcelona; Washington U., Seattle; Trieste Observ.; Calicut U.; Portsmouth U., ICG; Lund U.; LIneA, Rio de Janeiro; Carnegie Inst. Observ.; Barcelona, IFAE
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: 89243024CSC000002
• OSTI ID: 2998959
• Report Number(s): FERMILAB-PUB-25-0714-LDRD-PPD; oai:inspirehep.net:3069041; arXiv:2510.11684
• Journal Information: No journal information, Journal Name: No journal information
• Country of Publication: United States
• Language: English