Abstract / Description of output
We present homogeneous, sub-horizontal branch photometry of 20 dwarf
spheroidal satellite galaxies of M31 observed with the Hubble Space
Telescope. Combining our new data for 16 systems with archival data in
the same filters for another four, we show that Andromeda dwarf
spheroidal galaxies favor strikingly red horizontal branches or red
clumps down to ˜104.2 L ⊙ (M V
˜ -5.8). The age-sensitivity of horizontal branch stars
implies that a large fraction of the M31 dwarf galaxies have extended
star formation histories (SFHs), and appear inconsistent with early star
formation episodes that were rapidly shutdown. Systems fainter than
˜105.5 L ⊙ show the widest range in the
ratios and morphologies of red and blue horizontal branches, indicative
of both complex SFHs and a diversity in quenching timescales and/or
mechanisms, which is qualitatively different from what is currently
known for faint Milky Way (MW) satellites of comparable luminosities.
Our findings bolster similar conclusions from recent deeper data for a
handful of M31 dwarf galaxies. We discuss several sources for diversity
of our data such as varying halo masses, patchy reionization,
mergers/accretion, and the environmental influence of M31 and the Milky
Way on the early evolution of their satellite populations. A detailed
comparison between the histories of M31 and MW satellites would shed
signifiant insight into the processes that drive the evolution of
low-mass galaxies. Such a study will require imaging that reaches the
oldest main-sequence turnoffs for a significant number of M31
companions.
Original language | English |
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Pages (from-to) | 16 |
Journal | Astrophysical Journal |
Volume | 850 |
Issue number | 1 |
DOIs | |
Publication status | Published - 13 Nov 2017 |
Keywords / Materials (for Non-textual outputs)
- galaxies: dwarf
- galaxies: evolution
- galaxies: photometry
- Local Group