Dispersal timescale of protoplanetary disks in the low-metallicity young
  cluster Dolidze 25
  The dispersal of protoplanetary disks sets the timescale available for
planets to assemble, and thus it is one of the fundamental parameters in
theories of planetary formation. Disk dispersal is determined by several
properties of the central star, the disk itself, and the surrounding
environment. In particular, the metallicity of disks may impact their
evolution, even if to date controversial results exist: in low-metallicity
clusters disks seem to rapidly disperse, while in the Magellanic Clouds some
evidence supports the existence of accreting disks few tens of Myrs old. In
this paper we study the dispersal timescale of disks in Dolidze~25, the young
cluster in proximity of the Sun with lowest metallicity, with the aim of
understanding whether disk evolution is impacted by the low-metallicity of the
cluster. We have analyzed Chandra/ACIS-I observations of the cluster and
combined the resulting source catalog with existing optical and infrared
catalogs of the region. We selected the disk-bearing population and the
disk-less population of Dolidze 25. We have derived stellar parameters from
isochrones fitted to color-magnitude diagrams. We derived a disk fraction of
about 34% and a median age of 1.2 Myrs. By comparing this estimate with
existing estimates of the disk fraction of clusters younger than 10 Myrs, our
study suggests that the disk fraction of Dolidze 25 is lower than what is
expected from its age alone. Even if our results are not conclusive given the
intrinsic uncertainty on stellar ages estimated from isochrones fitting to
color-magnitude diagrams, we suggest that disk evolution in Dolidze 25 may be
impacted by the environment. Given the poor O star population and low stellar
density of the cluster, it is more likely that disks dispersal timescale is
dictated more by the low metallicity of the cluster rather than external
photoevaporation or dynamical encounters.
