On expansion parallax distances for planetary nebulae
Abstract
The distances to individual winddriven bubbles such as Planetary Nebulae (PNe) can be determined using expansion parallaxes: the angular expansion velocity in the sky is compared to the radial velocity of gas measured spectroscopically. Since the one is a pattern velocity, and the other a matter velocity, these are not necessarily the same. Using the jump conditions for both shocks and ionization fronts, I show that for typical PNe the pattern velocity is 20 to 30% larger than the material velocity, and the derived distances are therefore typically 20 to 30% too low. I present some corrected distances and suggest approaches to be used when deriving distances using expansion parallaxes.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 2004
 DOI:
 10.1051/00046361:20034485
 arXiv:
 arXiv:astroph/0312140
 Bibcode:
 2004A&A...416..623M
 Keywords:

 shock waves;
 planetary nebulae;
 stars: distances;
 stars: AGB and postAGB;
 hydrodynamics;
 ISM: planetary nebulae: general;
 Astrophysics
 EPrint:
 7 pages, 6 figures, accepted for publication in A&