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2000AJ....120..909A - Astron. J., 120, 909-919 (2000/August-0)
Optical and near-infrared study of the Cepheus E outflow, a very low-excitation object.
AYALA S., NORIEGA-CRESPO A., GARNAVICH P.M., CURIEL S., RAGA A.C., BOHM K.-H. and RAYMOND J.
Abstract (from CDS):
The optical spectroscopic characteristics of Cep E (HH 377) appear to be similar to the ones of low-excitation HH objects. However, the electron density determined from the [S II] λλ6731/6717 line ratio for this object (ne=4100 cm–3), and the [O I] λ6300/Hα, [S II] λλ(6717+6731)/Hα ratios are higher than the values of all of the previously studied low-excitation HH objects. This result is likely to be the consequence of an anomalously high environmental density in the HH 377 outflow. The ionization fraction obtained for HH 377 is xe∼1%. From this result, together with the observed [O I] λ6300/Hα line ratio, we conclude that the observed Hα line emission is collisionally excited. From a comparison with shock models, we also conclude that the extinction toward HH 377 is very low. Comparing the observed Hβ and Hα fluxes of HH 377 with model predictions, we determine a shock speed between 15 and 20 km.s–1, although somewhat higher velocities also produce spectra with line ratios that qualitatively agree with the observations of HH 377.
Abstract Copyright: ∼
Journal keyword(s): Infrared Radiation - ISM: individual (Cepheus E) - ISM: individual (HH 377) - ISM: Jets and Outflows
Simbad objects: 15
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