Abstract / Description of output
We present the star formation histories (SFHs) of 20 faint M31 satellites
(−12≲MV≲−6) that were measured by modeling sub-horizontal
branch (HB) depth color-magnitude diagrams constructed from Hubble Space
Telescope (HST) imaging. Reinforcing previous results, we find that virtually
all galaxies quenched between 3 and 9 Gyr ago, independent of luminosity, with
a notable concentration 3−6 Gyr ago. This is in contrast to the Milky Way
(MW) satellites, which are generally either faint with ancient quenching times
or luminous with recent (<3 Gyr) quenching times. We suggest that systematic
differences in the quenching times of M31 and MW satellites may be a reflection
of the varying accretion histories of M31 and the MW. This result implies that
the formation histories of low-mass satellites may not be broadly
representative of low-mass galaxies in general. Among the M31 satellite
population we identify two distinct groups based on their SFHs: one with
exponentially declining SFHs (τ∼2 Gyr) and one with rising SFHs with
abrupt quenching. We speculate how these two groups could be related to
scenarios for a recent major merger involving M31. The Cycle 27 HST Treasury
survey of M31 satellites will provide well-constrained ancient SFHs to go along
with the quenching times we measure here. The discovery and characterization of
M31 satellites with MV≳−6 would help quantify the relative
contributions of reionization and environment to quenching of the lowest-mass
satellites.
Original language | English |
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Number of pages | 7 |
Journal | Astrophysical Journal Letters |
Volume | 885 |
Issue number | 1 |
DOIs | |
Publication status | Published - 25 Oct 2019 |
Keywords / Materials (for Non-textual outputs)
- astro-ph.GA