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arXiv · 2504.18645

DELVE-DEEP Survey: The Faint Satellite System of NGC 55

Jonah Medoff·Burçin Mutlu-Pakdil·Jeffrey L. Carlin·Alex Drlica-Wagner·Erik J. Tollerud·Amandine Doliva-Dolinsky·David J. Sand·Clara E. Martínez-Vázquez·Guy S. Stringfellow·William Cerny·Denija Crnojević·Peter S. Ferguson·Catherine E. Fielder·Astha Chaturvedi·Nitya Kallivayalil·Noelia E. D. Noël·Kathy Vivas·Alistair R. Walker·Monika Adamów·Clecio R. Bom·Julio A. Carballo-Bello·Yumi Choi·Gustavo E. Medina·Mahdieh Navabi·Andrew B. Pace·Alex H. Riley·Joanna D. Sakowska
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Abstract

We report the first comprehensive census of the satellite dwarf galaxies around NGC 55 ($2.1$ Mpc) as a part of the DECam Local Volume Exploration DEEP (DELVE-DEEP) survey. NGC 55 is one of four isolated, Magellanic analogs in the Local Volume around which DELVE-DEEP aims to identify faint dwarfs and other substructures. We employ two complementary detection methods: one targets fully resolved dwarf galaxies by identifying them as stellar over-densities, while the other focuses on semi-resolved dwarf galaxies, detecting them through shredded unresolved light components. As shown through extensive tests with injected galaxies, our search is sensitive to candidates down to $M_V \lesssim -6.6$ and surface brightness $μ\lesssim 28.5$ mag arcsec$^{-2}$, and $\sim 80\%$ complete down to $M_V \lesssim -7.8$. We do not report any new confirmed satellites beyond two previously known systems, ESO 294-010 and NGC 55-dw1. We construct the satellite luminosity function of NGC 55 and find it to be consistent with the predictions from cosmological simulations. As one of the first complete luminosity functions for a Magellanic analog, our results provide a glimpse of the constraints on low-mass-host satellite populations that will be further explored by upcoming surveys, such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time.

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Jonah Medoff, Burçin Mutlu-Pakdil, Jeffrey L. Carlin, Alex Drlica-Wagner, Erik J. Tollerud, Amandine Doliva-Dolinsky, David J. Sand, Clara E. Martínez-Vázquez, Guy S. Stringfellow, William Cerny, Denija Crnojević, Peter S. Ferguson, Catherine E. Fielder, Astha Chaturvedi, Nitya Kallivayalil, Noelia E. D. Noël, Kathy Vivas, Alistair R. Walker, Monika Adamów, Clecio R. Bom, Julio A. Carballo-Bello, Yumi Choi, Gustavo E. Medina, Mahdieh Navabi, Andrew B. Pace, Alex H. Riley, Joanna D. Sakowska. 2025-09-02. DELVE-DEEP Survey: The Faint Satellite System of NGC 55. https://doi.org/10.3847/1538-4357%2Fadf211

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