Bibcode
DOI
García-Lario, Pedro; Riera, Angels; Manchado, A.
Bibliographical reference
The Astrophysical Journal, Volume 526, Issue 2, pp. 854-861.
Advertised on:
12
1999
Journal
Citations
28
Refereed citations
24
Description
Based on optical and near-infrared ground-based spectroscopy and optical
and near-infrared Hubble Space Telescope (HST) images, we confirm the
classification of Hen 401 as a bipolar proto-planetary nebula. HST
images reveal a highly elongated morphology, consisting of two main
bipolar lobes of unequal surface brightness separated by a dark lane of
dust with a total extension of 28''x3'',
superimposed on a much fainter background emission of elliptical shape
extending over ~10''x5''. The simultaneous
detection of spectral lines formed under very different density
conditions, together with the strong obscuration observed along the
equatorial plane, is interpreted as the signature of a circumstellar
disk, which would be responsible for the strong collimation observed. We
conclude that the emission observed is mainly due to scattering of the
light originated in the fluorescence-excited inner region of the
circumstellar disk. In addition, we also report the detection of strong
molecular H2 emission in the near infrared, confirming that
the onset of the H2 emission occurs in proto-PNs after the
bipolar structure has developed, but before photoionization takes place.