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The Hubble space telescope survey of M31 Satellite Galaxies. I. RR Lyrae–based distances and refined 3D geometric structure


Savino, A and Weisz, DR and Skillman, ED and Dolphin, A and Kallivayalil, N and Cole, AA and Collins, MLM and Cooper, MC and Deason, AJ and Dotter, AL and Fardal, M and Ferguson, AMN and Fritz, TK and Geha, MC and Gilbert, KM and Guhathakurta, P and Ibata, R and Irwin, MJ and Jeon, M and Kirby, E and Lewis, GF and Mackey, D and Majewski, SR and Martin, N and McConnachie, A and Patel, E and Rich, RM and Simon, JD and Sohn, ST and Tollerud, EJ and van der Marel, RP, The Hubble space telescope survey of M31 Satellite Galaxies. I. RR Lyrae-based distances and refined 3D geometric structure, The Astrophysical Journal, 938, (2) Article 101. ISSN 0004-637X (2022) [Refereed Article]

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DOI: doi:10.3847/1538-4357/ac91cb


We measure homogeneous distances to M31 and 38 associated stellar systems (−16.8 ≤ MV ≤ −6.0), using time-series observations of RR Lyrae stars taken as part of the Hubble Space Telescope Treasury Survey of M31 Satellites. From >700 orbits of new/archival Advanced Camera for Surveys imaging, we identify >4700 RR Lyrae stars and determine their periods and mean magnitudes to a typical precision of 0.01 day and 0.04 mag. Based on period–Wesenheit–metallicity relationships consistent with the Gaia eDR3 distance scale, we uniformly measure heliocentric and M31-centric distances to a typical precision of ∼20 kpc (3%) and ∼10 kpc (8%), respectively. We revise the 3D structure of the M31 galactic ecosystem and: (i) confirm a highly anisotropic spatial distribution such that ∼80% of M31's satellites reside on the near side of M31; this feature is not easily explained by observational effects; (ii) affirm the thin (rms 7–23 kpc) planar "arc" of satellites that comprises roughly half (15) of the galaxies within 300 kpc from M31; (iii) reassess the physical proximity of notable associations such as the NGC 147/185 pair and M33/AND xxii; and (iv) illustrate challenges in tip-of-the-red-giant branch distances for galaxies with MV > − 9.5, which can be biased by up to 35%. We emphasize the importance of RR Lyrae for accurate distances to faint galaxies that should be discovered by upcoming facilities (e.g., Rubin Observatory). We provide updated luminosities and sizes for our sample. Our distances will serve as the basis for future investigation of the star formation and orbital histories of the entire known M31 satellite system.

Item Details

Item Type:Refereed Article
Keywords:dwarf galaxies, variable stars, distance measurement, Andromeda Galaxy
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Cole, AA (Professor Andrew Cole)
ID Code:154099
Year Published:2022
Web of Science® Times Cited:2
Deposited By:Physics
Deposited On:2022-10-28
Last Modified:2023-01-10

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