Аннотация
A recent surprise in stellar cluster research, made possible through the
precision of Hubble Space Telescope photometry, was that some intermediate age
(1-2 Gyr) clusters in the Large and Small Magellanic Clouds have main sequence
turn-off (MSTO) widths that are significantly broader than would be expected
for a simple stellar population (SSP). One interpretation of these extended
MSTOs (eMSTOs) is that age spreads of the order of ~500 Myr exist within the
clusters, radically redefining our view of stellar clusters, which are
traditionally thought of as single age, single metallicity stellar populations.
Here we test this interpretation by studying other regions of the CMD that
should also be affected by such large age spreads, namely the width of the
sub-giant branch (SGB) and the red clump (RC). We study two massive clusters in
the LMC that display the eMSTO phenomenon (NGC 1806 & NGC 1846) and show that
both have SGB and RC morphologies that are in conflict with expectations if
large age spreads exist within the clusters. We conclude that the SGB and RC
widths are inconsistent with extended star-formation histories within these
clusters, hence age spreads are not likely to be the cause of the eMSTO
phenomenon. Our results are in agreement with recent studies that also have
cast doubt on whether large age spreads can exist in massive clusters; namely
the failure to find age spreads in young massive clusters, a lack of gas/dust
detected within massive clusters, and homogeneous abundances within clusters
that exhibit the eMSTO phenomenon.
Пользователи данного ресурса
Пожалуйста,
войдите в систему, чтобы принять участие в дискуссии (добавить собственные рецензию, или комментарий)