The Arches cluster out to its tidal radius: dynamical mass segregation
  and the effect of the extinction law on the stellar mass function
  The Galactic center is the most active site of star formation in the Milky
Way Galaxy, where particularly high-mass stars have formed very recently and
are still forming today. However, since we are looking at the Galactic center
through the Galactic disk, knowledge of extinction is crucial when studying
this region. The Arches cluster is a young, massive starburst cluster near the
Galactic center. We observed the Arches cluster out to its tidal radius using
Ks-band imaging obtained with NAOS/CONICA at the VLT combined with Subaro/Cisco
J-band data to gain a full understanding of the cluster mass distribution. We
show that the determination of the mass of the most massive star in the Arches
cluster, which had been used in previous studies to establish an upper mass
limit for the star formation process in the Milky Way, strongly depends on the
assumed slope of the extinction law. Assuming the two regimes of widely used
infrared extinction laws, we show that the difference can reach up to 30% for
individually derived stellar masses and Delta AKs ~ 1 magnitude in acquired
Ks-band extinction, while the present-day mass function slope changes by ~ 0.17
dex. The present-day mass function slope derived assuming the more recent
extinction law increases from a flat slope of alpha_{Nishi}=-1.50 \pm0.35 in
the core (r<0.2 pc) to alpha_{Nishi}=-2.21 \pm0.27 in the intermediate annulus
(0.2 <r<0.4 pc), where the Salpeter slope is -2.3. The mass function steepens
to alpha_{Nishi}=-3.21 \pm0.30 in the outer annulus (0.4<r<1.5 pc), indicating
that the outer cluster region is depleted of high-mass stars. This picture is
consistent with mass segregation owing to the dynamical evolution of the
cluster.
