Bibcode
DOI
Cuesta, L.; Phillips, J. P.
Referencia bibliográfica
The Astronomical Journal, Volume 120, Issue 5, pp. 2661-2669.
Advertised on:
11
2000
Número de citas
6
Número de citas referidas
5
Descripción
We have acquired narrowband imaging of NGC 3587 (the Owl Nebula) in the
transitions [O II] λλ3727, 3729, H I λ4861, [O III]
λ5007, H I λ6563, [N II] λ6584, [S II]
λ6717, and [S II] λ6731. As a result, we are able to
evaluate the variation of excitation and electron density over the
projected envelope of the source. We propose that the Owl Nebula
consists of four primary shells: an internal, tilted, barrel-like
component responsible for higher excitation emission; two much more
uniform, spherically symmetric structures, CSCI and CSCII. These,
finally, are enveloped by a much lower intensity, lower excitation halo,
dubbed CSCIII. A large proportion of the low-excitation emission appears
to be associated with the periphery of CSCI, and it is conceivable that
this is, physically speaking, a relatively thin-shelled structure. [S
II] density mapping appears to indicate that ne is
preferentially enhanced toward the northern periphery of the shell, in a
regime where low-excitation line strengths are also preferentially
enhanced. We suggest that such trends may arise through northerly
shocking of the shell CSCI. There is, in addition, some evidence for an
east-west dichotomy in density structure, which may reflect variable
sampling of the higher density, barrel-like component. Mean densities
are low, and of the order =590 cm-3.