Resolving the inner regions of the HD97048 circumstellar disk with
  VLT/NACO polarimetric differential imaging
  Circumstellar disks are the cradles of planetary systems and their physical
and chemical properties directly influence the planet formation process. As
most planets supposedly form in the inner disk regions, i.e., within a few tens
of AU, it is crucial to study circumstellar disk on these scales to constrain
the conditions for planet formation. Our aims are to characterize the inner
regions of the circumstellar disk around the young Herbig Ae/Be star HD97048 in
polarized light. We use VLT/NACO to observe HD97048 in polarimetric
differential imaging (PDI) mode in the H and Ks band. We spatially resolve the
disk around HD97048 in polarized flux in both filters on scales between
~0.1"-1.0" corresponding to the inner ~16-160 AU. Fitting isophots to the flux
calibrated H-band image between 13 - 14 mag/arcsec^2 and 14 - 15 mag/arcsec^2
we derive a apparent disk inclination angle of 34+-5 deg and 47+-2 deg,
respectively. The disk position angle in both brightness regimes is almost
identical and roughly 80 deg. Along the disk major axis the surface brightness
of the polarized flux drops from ~11 mag/arcsec^2 at ~0.1" (~16 AU) to ~15.3
mag/arcsec^2 at ~1.0" (~160 AU). The brightness profiles along the major axis
are fitted with power-laws falling off as ~r^(-1.78+-0.02) in H and
~r^(-2.34+-0.04) in Ks. As the surface brightness drops off more rapidly in Ks
compared to H the disks becomes relatively bluer at larger separations possibly
indicating changing dust grain properties as a function of radius. For the
first time the inner ~0.1"-1.0" (~16-160 AU) of the surface layer of the
HD97048 circumstellar disk have been imaged in scattered light demonstrating
the power of ground-based imaging polarimetry. Our data fill an important gap
in a large collection of existing data including resolved thermal dust and PAH
emission images as well as resolved gas emission lines.
