Variable jets with non-top hat ejection cross sections: a model for the knots of the HH 34 jet

Abstract

We compute axisymmetric, single-sinusoidal mode variable ejection models with a non-top hat ejection velocity cross section. We find that for decreasing edge-to-center velocity ratios one obtains internal working surfaces with progressively more extended bow shock wings. These wings produce [S II] emission which partially fills in the inter-knot regions in predicted intensity maps. We then compute 3-mode models (with parameters appropriate for the HH 34 jet), and compare predicted intensity maps with archival HST images of HH 34. We find that a model with a moderate edge-to-center velocity ratio produces knot structures with morphologies and time-variabilites with clear similarities to the observations of HH 34.