AAS 207th Meeting, 8-12 January 2006
Session 175 Recent Discoveries in the Far UV
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

Previous   |   Session 175   |   Next  |   Author Index   |   Block Schedule

[175.19] Molecular and Atomic Excitation Stratification in the Outflow of the Planetary Nebula M27

S. R. McCandliss (JHU)

The velocity structure of outward moving atomic and molecular material in the planetary nebula M27 (the Dumbbell) as revealed by STIS and {\em FUSE} absorption line spectroscopy and Dwingeloo 21 cm observations is presented. Comparisons are made to the velocity profiles of H\alpha, [\ion{N}{2}] \lambda 6584 and [\ion{O}{3}] \lambda5007 emission observed by Meaburn et al. (2005, 1992) and CO (2-1) 230 GHz emission observed by Bachiller et al. (2002). Highly excited molecular hydrogen is found at velocities between -30 and -35 km s-1, blueshifted from the central star (RV \approx -40 km s-1). The molecular hydrogen appears at a transition velocity demarcating a high ionization, low velocity flow (-10\lesssim vhi \lesssim -30 km s-1) from a low ionization zone, high velocity flow (-30\lesssim vlow \lesssim -50 km s-1). \ion{H}{1} absorption is found in the low ionization zone, consistent with four velocity components between -35 and -59 km s-1. Molecular hydrogen ro-vibrational excitation shows statistically significant deviation from pure thermal excitation at a temperature of 2040 K. It is incompatable with the excitation expected from continuum fluorescence, but may be compatable with expectations for the recently discovered Ly\alpha fluorescence pumping of hot thermal molecular discussed by Lupu et al. (this meeting).

In addition, the line of sight nebular material produces no reddening of the stellar continuum. This is at odds with the dust extinction (E(\bv) \approx 0.1) inferred from H\alpha/H\beta line ratios. I discuss dissociation channels for molecular hydrogen (or its ion) that might result in a preferential enhancement of H\alpha/H\beta, relative to that expected from radiative recombination, and thereby mimic the effect of extinction. The consequence of low dust content, atomic and molecular excitation and velocity statification are discussed in the context of molecular clump formation models for planetary nebulae.

This work is supported by NASA grant NNGO4GK82G to the Johns Hopkins University.

If you would like more information about this abstract, please follow the link to http://www.pha.jhu.edu/~stephan/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: stephan@pha.jhu.edu

Previous   |   Session 175   |   Next

Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.