Main-sequence stars masquerading as Young Stellar Objects in the central
  molecular zone
  In contrast to most other galaxies, star-formation rates in the Milky Way can
be estimated directly from Young Stellar Objects (YSOs). In the Central
Molecular Zone (CMZ) the star-formation rate calculated from the number of YSOs
with 24 microns emission is up to order of magnitude higher than the value
estimated from methods based on diffuse emission (such as free-free emission).
Whether this effect is real or whether it indicates problems with either or
both star formation rate measures is not currently known. In this paper, we
investigate whether estimates based on YSOs could be heavily contaminated by
more evolved objects such as main-sequence stars. We present radiative transfer
models of YSOs and of main-sequence stars in a constant ambient medium which
show that the main-sequence objects can indeed mimic YSOs at 24 microns.
However, we show that in some cases the main-sequence models can be marginally
resolved at 24 microns, whereas the YSO models are always unresolved. Based on
the fraction of resolved MIPS 24 microns sources in the sample of YSOs
previously used to compute the star formation rate, we estimate the fraction of
misclassified "YSOs" to be at least 63%, which suggests that the star-formation
rate previously determined from YSOs is likely to be at least a factor of three
too high.
