A rogues gallery of Andromeda's dwarf galaxies II. Precise Distances to 17 Faint Satellites

Abstract

We present new horizontal branch (HB) distance measurements to 17 of the faintest known M31 satellites ($-6\lesssim M_V\lesssim -13$) based on deep Hubble Space Telescope (HST) imaging. The color-magnitude diagrams extend $\sim$1-2 magnitudes below the HB, which provides for well-defined HBs, even for faint galaxies in which the tip of the red giant branch (TRGB) is sparsely populated. We determine distances across the sample to an average precision of 4% ($\sim 30$~kpc at $800$~kpc). We find that the majority of these galaxies are in good agreement, though slightly farther (0.1-0.2 mag) when compared to recent ground-based TRGB distances. Two galaxies (And~IX and And~XVII) have discrepant HST and ground-based distances by $\sim 0.3$ mag ($\sim 150$~kpc), which may be due to contamination from Milky Way foreground stars and/or M31 halo stars in sparsely populated TRGB regions. We use the new distances to update the luminosities and structural parameters for these 17 M31 satellites. The new distances do not substantially change the spatial configuration of the M31 satellite system. We comment on future prospects for precise and accurate HB distances for faint galaxies in the Local Group and beyond.

8 pages, 3 figures. Accepted for publication in MNRAS

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• Andromeda XXI -- a dwarf galaxy in a low density dark matter halo
• Can cosmological simulations capture the diverse satellite populations of observed Milky Way analogues?
• Radial Distributions of Dwarf Satellite Systems in the Local Volume
• Comparing the Quenching Times of Faint M31 and Milky Way Satellite Galaxies
• Tucana B: A Potentially Isolated and Quenched Ultra-faint Dwarf Galaxy at D$\approx$1.4 Mpc
• The infall of dwarf satellite galaxies are influenced by their host's massive accretions
• Solo dwarfs III: Exploring the orbital origins of isolated Local Group galaxies with Gaia Data Release 2
• An updated detailed characterization of planes of satellites in the MW and M31
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• Saying Hallo to M94's Stellar Halo: Investigating the Accretion History of the Largest Pseudobulge Host in the Local Universe
• The Isaac Newton Telescope Monitoring Survey of Local Group Dwarf Galaxies. VI. The Star Formation History and Dust Production in Andromeda IX
• Anomalous Stellar Populations in LSB Galaxies
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• The frozen outskirts: a cold Hubble flow and the mass of the Local Group
• Pisces VII: Discovery of a possible satellite of Messier 33 in the DESI Legacy Imaging Surveys