The Faint Satellite System of NGC 253: Insights into Low-density Environments and No Satellite Plane
Caldwell, Nelson; Strader, Jay; Seth, Anil C.; Sand, David J.; Jones, Michael G.; Zaritsky, Dennis; Simon, Joshua D.; Guhathakurta, Puragra; Toloba, Elisa; Fielder, Catherine E.; Bennet, Paul; Crnojević, Denija; Karunakaran, Ananthan; Mutlu-Pakdil, Burçin; Spekkens, Kristine
United States, Canada
Abstract
We have conducted a systematic search around the Milky Way (MW) analog NGC 253 (D = 3.5 Mpc), as a part of the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS)—a Magellan+Megacam survey to identify dwarfs and other substructures in resolved stellar light around MW-mass galaxies outside of the Local Group. In total, NGC 253 has five satellites identified by PISCeS within 100 kpc with an absolute V-band magnitude of M V < ‑7. We have additionally obtained deep Hubble Space Telescope imaging of four reported candidates beyond the survey footprint: Do III, Do IV, and dw0036m2828 are confirmed to be satellites of NGC 253, while SculptorSR is found to be a background galaxy. We find no convincing evidence for the presence of a plane of satellites surrounding NGC 253. We construct its satellite luminosity function, which is complete down to M V ≲ ‑8 out to 100 kpc and M V ≲ ‑9 out to 300 kpc, and compare it to those calculated for other Local Volume galaxies. Exploring trends in satellite counts and star-forming fractions among satellite systems, we find relationships with host stellar mass, environment, and morphology, pointing to a complex picture of satellite formation, and a successful model has to reproduce all of these trends. *This paper includes data gathered with the 6.5 m Magellan Telescope at Las Campanas Observatory, Chile.