A distance scale of planetary nebulae based on mid-infrared data
  Some of the most successful statistical methods for obtaining distances of
planetary nebulae (PNe) are based on their apparent sizes and radio emission
intensities. These methods have the advantage of being "extinction-free" and
are especially suited to be applied to PNe situated at large distances. A
similar method, based on the mid-infrared (MIR) emission of PNe, would have the
advantage of being applicable to the large databases created after the various
all-sky or Galactic plane infrared surveys, such as IRAS, MSX, ISOGAL, GLIMPSE,
etc. In this work we propose a statistical method to calculate the distance of
PNe based on the apparent nebular radius and the MIR flux densities. We show
that the specific intensity between 8 and 21 micron is proportional to the
brightness temperature T_b at 5 GHz. Using MIR flux densities at 8, 12, 15 and
21 microns from the MSX survey, we calibrate the distance scale with a
statistical method by Stanghellini et al. 2008 (SSV). The database used in the
calibration consisted of 67 Galactic PNe with MSX counterparts and distances
determined by SSV. We apply the method to a sample of PNe detected at 8 microns
in the GLIMPSE infrared survey, and determine the distance of a sample of PNe
located along the Galactic plane and bulge.
