Shock excitation of the knots of Hen 3-1475

¹ Departament de Física i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Av. Víctor Balaguer s/n, 08800 Vilanova i la Geltrú, Spain e-mail: angels.riera@upc.edu
² Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
³ Instituto de Astronomía, UNAM, A. Postal 70-264, 04510 México, México e-mail: binette@astroscu.unam.mx
⁴ Instituto de Ciencias Nucleares, UNAM, A. Postal 70-543, 04510 México, México e-mail: raga@nucleares.unam.mx

Received: 23 May 2005
Accepted: 2 May 2006

Abstract

We present new optical STIS HST spectroscopic observations of the jets of the proto-planetary nebula Hen 3-1475. The excitation conditions of the knots of Hen 3-1475 are derived from the observed optical spectra, confirming that the knots are shock excited. The shocked spectra are qualitatively reproduced by simple “3/2”D bow shock models. We present a set of bow shock models devoted to planetary nebulae, and discuss the effects of the pre-ionization conditions, the bow shock velocity, the bow shock shape and the chemical abundances on the predicted spectra. To explore the reliability of the “3/2”D bow shock models, we also compare the observed spectra of other three proto-planetary nebulae (M 1–92, M 2–56 and CRL 618) to the predicted spectra.