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whwiii
2010-Jun-06, 10:52 PM
hello
i've been reading up on abell 35
having recently imaged it in Ha and OIII
http://whwastro.homestead.com/files/abell-35-Ha-OIII.jpg
but don't quite understand the phenomena in this article (includes link to full pdf):
http://adsabs.harvard.edu/abs/1996ApJ...456..644H

the article describes three things which i can't quite grasp:
1. a systemic wind moving at Mach 1.3 with respect to the PN medium to give rise to the bow shock morphology. (the blue OIII structure)
-i had assumed it was created by the PN interacting with the interstellar medium.
2. PN-ISM interaction as a Mach 10 shock which gives rise to two prominent linear features as a result of an inhomogeneous PN ejection mechanism (the red Ha structures "pipes")
3. what about the nebula is "inside-out"? interstellar medium inside it?

thanks

-bill w

astro.whwiii.net

ngc3314
2010-Jun-07, 12:41 PM
As the planetary nebula (or almost any other gaseous mass) expands into the interstellar medium, just as a shock front develops when the expansion is faster than the sound speed in the material, a reverse shock develops as the freely outflowing gas reaches the gas which has piled up at the shock. This reverse shock moves "backwards" (sometimes faster than the sound speed), usually not as fast as the outflow velocity so the whole pattern may still expand. Here (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1991AJ....102.1381S&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf) is one paper with simulations of planetary nebulae showing reverse shocks being set up.

whwiii
2010-Jun-08, 04:43 AM
thanks for the reply. still trying to sink my teeth into the paper you link to. can you shed any light on the mach 10 shock causing the "pipes".