Distances to Planetary Nebulae BD +30 degrees 3639 and NGC 6572
Abstract
Thirdepoch Very Large Array propermotion measurements on the planetary nebulae BD +30°3639 and NGC 6572 have been made. Combining these measurements with simple models for the nebulae and using improved analysis, it has been determined that the distance to BD +30°3639 is 1.5±0.4 kpc and NGC 6572 is 1.2±0.4 kpc. These measurements are consistent with the distances determined from the previous epoch. However, the errors are significantly smaller and are now dominated not by the measurements but by the modeling and the uncertainty in the flux variation. The distances are significantly higher than those determined by statistical methods, with important consequences for calculation of the nebular masses and luminosities.
In addition to their distances, the observations have elucidated the dynamical properties of the objects. First, the expansion of a shell is consistent with the selfsimilar expansion that is usually assumed for these objects, with the magnitude of the proper motion of a portion of a shell being linearly related to its distance from the center of symmetry. Second, the propermotion measurements have directly yielded the ages for the nebulae, which are determined to be 900±200 yr for BD +3003639 and 1000±200 yr for NGC 6572.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 1996
 DOI:
 10.1086/177054
 Bibcode:
 1996ApJ...461..282K
 Keywords:

 ASTROMETRY;
 ISM: GENERAL;
 ISM: KINEMATICS AND DYNAMICS;
 ISM: PLANETARY NEBULAE: INDIVIDUAL ALPHANUMERIC: BD +30 DEGREES 3639;
 RADIO CONTINUUM: ISM