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| Paper: |
The Star Formation History in the Far Outer Disc of M31:
A Recent Burst Triggered by Interaction with M33? |
| Volume: |
458, Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way |
| Page: |
315 |
| Authors: |
Bernard, E. J.; Ferguson, A. M. N.; Barker, M. K. |
| Abstract: |
We present the star formation history (SFH) of two fields located in the far
outer discs of M31 and M33 based on HST/ACS color-magnitude diagrams (CMD)
reaching the oldest main-sequence turn-offs. The SFHs were obtained using the
CMD-fitting technique. We find that both galaxies underwent a significant burst
of star formation 2 Gyr ago, that lasted ∼1.5 Gyr and is responsible for
about 25% of the total stellar mass in each field-of-view. In both galaxies,
this burst is also accompanied by a decline in global metallicity, usually a
clear signature of the inflow of metal-poor gas. Interestingly, dynamical models
of the M31-M33 interaction favour ∼2–3 Gyr ago as the last pericentric
passage when the systems were within ∼40 kpc of each other, which is coeval
with the beginning of the burst. This suggests that the burst of star formation
in the outer discs of both galaxies may have been triggered by the interaction. |
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