DELVE Milky Way Satellite Galaxy Census. I. Satellite Population and Survey Selection Function in DES, DELVE, and Pan-STARRS

Journal Article · Fri Mar 13 00:00:00 UTC 2026 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/ae4479 · OSTI ID:2997195

Tan, Chin Yi  ^[1]; Drlica-Wagner, A. ; Pace, A. B. ; Cerny, W. ; Nadler, E. O. ; Doliva-Dolinsky, A. ; Anbajagane, D. ; Li, T. S. ; Simon, J. D. ; Vivas, A. K. ; Walker, A. R. ; Adamów, M. ; Bechtol, K. ; Carlin, J. L. ; Casey, Q. O. ; Chang, C. ; Chaturvedi, A. ; Cheng, T.-Y. ; Chiti, A. ; Choi, Y. ; Crnojević, D. ; Ferguson, P. S. ; Gruendl, R. A. ; Ji, A. P. ; Limberg, G. ; Medina, G. E. ; Mutlu-Pakdil, B. ; Noël, N. E. D. ; Overdeck, K. ; Placco, V. M. ; Riley, A. H. ; Sand, D. J. ; Sharp, J. ; Sherman, N. F. ; Stringfellow, G. S. ; Wechsler, R. H. ; Aguena, M. ; Allam, S. ; Alves, O. ; Bacon, D. ; Brooks, D. ; Burke, D. L. ; Camilleri, R. ; Carballo-Bello, J. A. ; Carnero Rosell, A. ; Carretero, J. ; da Costa, L. N. ; da Silva Pereira, M. E. ; Davis, T. M. ; De Vicente, J. ; Desai, S. ; Everett, S. ; Flaugher, B. ; Frieman, J. ; García-Bellido, J. ; Gruen, D. ; Gutierrez, G. ; Herner, K. ; Hinton, S. R. ; Hollowood, D. L. ; James, D. J. ; Kuehn, K. ; Lahav, O. ; Lee, S. ; Marshall, J. L. ; Martínez-Vázquez, C. E. ; Massana, P. ; Mena-Fernández, J. ; Miquel, R. ; Muir, J. ; Myles, J. ; Ogando, R. L. C. ; Plazas Malagón, A. A. ; Porredon, A. ; Sanchez, E. ; Sanchez Cid, D. ; Sevilla-Noarbe, I. ; Smith, M. ; Suchyta, E. ; Swanson, M. E. C. ; To, C. ; Tollerud, E. J. ; Tucker, D. L. ; Vikram, V.; Weaverdyck, N. ; Yamamoto, M. ; Zenteno, A.

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1. Univ. of Chicago, IL (United States); NSF-Simons AI Institute for the Sky (SkAI), Chicago, IL (United States); DELVE and DES Collaborations. et al.

The properties of Milky Way satellite galaxies have important implications for galaxy formation, reionization, and the fundamental physics of dark matter. However, the population of Milky Way satellites includes the faintest known galaxies, and current observations are incomplete. To understand the impact of observational selection effects on the known satellite population, we perform rigorous, quantitative estimates of the Milky Way satellite galaxy detection efficiency in three wide-field survey datasets: the Dark Energy Survey Year 6, the DECam Local Volume Exploration Data Release 3, and the Pan-STARRS1 Data Release 1. Together, these surveys cover ∼13,600 deg² to g ∼ 24.0 and ∼27,700 deg² to g ∼ 22.5, spanning ∼91% of the high-Galactic-latitude sky (∣b∣ ≥ 15°). We apply multiple detection algorithms over the combined footprint and recover 49 known satellites above a strict census detection threshold. To characterize the sensitivity of our census, we run our detection algorithms on a large set of simulated galaxies injected into the survey data, which allows us to develop models that predict the detectability of satellites as a function of their properties. We then fit an empirical model to our data and infer the luminosity function, radial distribution, and size–luminosity relation of Milky Way satellite galaxies. Our empirical model predicts a total of $$265^{+79}_{-47}$$ satellite galaxies with −20 ≤ M_V ≤ 0, half-light radii of 15 ≤ r_1/2, (pc) ≤ 3000, and galactocentric distances of 10 ≤ D_GC(kpc) ≤ 300. We also identify a mild anisotropy in the angular distribution of the observed galaxies, at a significance of ∼2σ, which can be attributed to the clustering of satellites associated with the LMC.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: 89243024CSC000002
• OSTI ID: 2997195
• Report Number(s): DES--2025-0909; FERMILAB-PUB--25-0573-LDRD-PPD; oai:inspirehep.net:2970131; arXiv:2509.12313
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 1000; ISSN 0004-637X; ISSN 1538-4357
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English