Expansion Parallax Distances to Planetary Nebulae

Details Expansion Parallax Distances to Planetary Nebulae Expansion Parallax Distances to Planetary Nebulae

Feb 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999noao.prop..220h&link_type=abstract

NOAO Proposal ID #1999A-0220

Mathematics

Logic

Scientific paper

The standard method for determining planetary nebulae (PNe) distances is indirect. A physical quantity is assumed to be common to and constant for all PNe, yielding fractional distance uncertainties > 150%, and distances suitable only for statistical surveys. As a result, distances to many extragalactic PNe are more accurately known than distances to most galactic PNe! Without accurate distances to individual PNe, some of the most important astrophysical properties of PNe remain obscure after centuries of observations. Among these are mass and luminosity, both of which are important for several critical projects including stellar evolution and mass loss, the PNe luminosity function, and the cosmological distance scale. We have started a program of individual distance measurements using expansion parallaxes of about 30 PNe measured from our multiepoch WFPC2 survey. Our calculations and extant results indicate that the accuracy of expansion distances is limited by knowledge of the nebular geometry. We request time on the long-slit Echelles at KPNO and CTIO to determine the Doppler expansion patterns along the targets' major and minor axes in the lines used for the WFPC2 survey (i.e., [N II] and [O III]). The Echelle time requirements are modest since the target surface brightnesses are high.

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