Bibcode
Davidge, T. J.; McConnachie, A. W.; Fardal, M. A.; Fliri, J.; Valls-Gabaud, D.; Chapman, S. C.; Lewis, G. F.; Rich, R. M.
Bibliographical reference
The Astrophysical Journal, Volume 751, Issue 1, article id. 74 (2012).
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5
2012
Journal
Citations
24
Refereed citations
22
Description
We examine the star-forming history of the M31 disk during the past few
hundred Myr. The luminosity functions (LFs) of main-sequence stars at
distances R GC > 21 kpc (i.e., >4 disk scale lengths)
are matched by models that assume a constant star formation rate (SFR).
However, at smaller R GC the LFs suggest that during the past
~10 Myr the SFR was 2-3 times higher than during the preceding ~100 Myr.
The rings of cool gas that harbor a significant fraction of the current
star-forming activity are traced by stars with ages ~100 Myr, indicating
that (1) these structures have ages of at least 100 Myr and (2) stars in
these structures do not follow the same relation between age and random
velocity as their counterparts throughout the disks of other spiral
galaxies, probably due to the inherently narrow orbital angular momentum
distribution of the giant molecular clouds in these structures. The
distribution of evolved red stars is not azimuthally symmetric, in the
sense that the projected density along the northeast segment of the
major axis is roughly twice that on the opposite side of the galaxy. The
northeast arm of the major axis thus appears to be a fossil star-forming
area that dates to intermediate epochs. Such a structure may be the
consequence of interactions with a companion galaxy.
Based on observations obtained with MegaPrime/MegaCam, a joint project
of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT),
which is operated by the National Research Council (NRC) of Canada, the
Institut National des Sciences de l'Univers of the Centre National de la
Recherche Scientifique (CNRS) of France, and the University of Hawaii.