Hubble Space Telescope Observations of NGC 253 Dwarf Satellites: Discovery of Three Ultra-faint Dwarf Galaxies

Abstract

We present deep Hubble Space Telescope imaging of five faint dwarf galaxies associated with the nearby spiral NGC 253 (D≈3.5 Mpc). Three of these are newly discovered ultra-faint dwarf galaxies, while all five were found in the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), a Magellan+Megacam survey to identify faint dwarfs and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data reach 3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances, structural parameters, and luminosities. All five systems contain predominantly old, metal-poor stellar populations (age∼12 Gyr, [M/H] −1.5) and have sizes (r h ∼110-3000 pc) and luminosities (M V ∼−7 to −12 mag) largely consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered beyond the Local Group. We also use archival H i data to place limits on the gas content of our discoveries. Deep imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come.

The Exploration of Local VolumE Satellites (ELVES) Survey: A Nearly Volume-Limited Sample of Nearby Dwarf Satellite Systems

“…In recent years, numerous groups have started work on the formidable observational task of surveying the very low-mass satellites of nearby (D 50 Mpc) massive hosts. Many groups have used deep, wide-field imaging or spectroscopic surveys to catalog candidate satellites around various hosts in the LV, including MW-mass hosts (e.g Irwin et al 2009;Kim et al 2011;Sales et al 2013;Spencer et al 2014;Merritt et al 2014;Karachentsev et al 2015b;Bennet et al 2017Bennet et al , 2019Bennet et al , 2020Tanaka et al 2017;Danieli et al 2017Danieli et al , 2020Smercina et al 2018;Kondapally et al 2018;Park et al 2017Park et al , 2019Byun et al 2020;Davis et al 2021;Garling et al 2021;Mutlu-Pakdil et al 2021a) and hosts of somewhat lower mass (Carlin et al 2016(Carlin et al , 2021Müller & Jerjen 2020;Drlica-Wagner et al 2021) and higher mass (Stierwalt et al 2009;Trentham & Tully 2009;Chiboucas et al 2009Chiboucas et al , 2013Crnojević et al 2014Crnojević et al , 2016Crnojević et al , 2019Müller et al 2015Müller et al , 2017aMüller et al , 2018aMüller et al , 2019bMüller et al , 2021Smercina et al 2017;Cohen et al 2018) mass. Pushing to lar...…”

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

“…Some hints for anisotropy in the satellite distribution are also evident around NGC 2750 based on 7 satellites, which may form part of a lower mass analogue to the satellite plane around Centaurus A (Paudel et al 2021). There is also evidence for a satellite plane around M81 (Chiboucas et al 2013) andNGC 253 (Martínez-Delgado et al 2021;Mutlu-Pakdil et al 2021).…”

Forward-modelling the Luminosity, Distance, and Size distributions of the Milky Way Satellites

“…We also add the recently discovered MW candidate dwarf galaxy Eridanus IV from Cerny et al (2021a). We also plot the data from other Local Volume dwarf galaxies (e.g., Sharina et al 2008;McConnachie 2012;Romanowsky et al 2016;Carlin et al 2016;Crnojević et al 2019;Martínez-Delgado et al 2021;Mutlu-Pakdil et al 2021c;Carlin et al 2021). (Right) The 2D distribution of our model dwarf galaxies in absolute V-band magnitude (𝑀 V ) and surface brightness (𝜇 V ) space (that is surface brightness -luminosity plane).…”

“…These predictions were born out by observations so far, which showed that UFDs have formed most of their stars very early (Tolstoy et al 2009;Brown et al 2012Brown et al , 2014Weisz et al 2014;Sacchi et al 2021) and their stellar populations are very metal poor (see Simon 2019, for a review). Due to the broad cosmological significance of dwarf galaxies, observational searches ★ E-mail: virajmanwadkar@gmail.com † E-mail: kravtsov@uchicago.edu for faintest and lowest surface brightness galaxies have been the subject of much observational effort over the past two decades (e.g., Belokurov et al 2010;McConnachie 2012;Koposov et al 2015;Bechtol et al 2015;Martin et al 2015;Drlica-Wagner et al 2015a;Kim et al 2016b;Muñoz et al 2018;Longeard et al 2018;Homma et al 2019;Mau et al 2020;Cerny et al 2021a;Martínez-Delgado et al 2021;Mutlu-Pakdil et al 2021b).…”