Context. HH 444 is one of the first Herbig-Haro (HH) jets discovered within a photoionized region.Aims. We re-analyze the Hα and red [S II] HST images of HH 444, and calculate the width of the jet as a function of distance from the source. We compare the Hα image with predictions from variable ejection velocity jet models. Methods. The determination of the jet's width is done with a non-parametric, wavelet analysis technique. The axisymmetric, photoionized jet simulations are used to predict Hα maps that can be directly compared with the observations. Results. Starting with a thin jet (unresolved at the resolution of the observations), we are able to produce knots with widths and morphologies that generally agree with the Hα knots of HH 444. This agreement is only obtained if the jet axis is at a relatively large, ∼45 • angle with respect to the sky. This agrees with previous spectroscopic observations of the HH 444 bow shock, which imply a relatively large jet axis/plane of the sky angle. Conclusions. We conclude that the general morphology of the chain of knots close to V510 Ori (the HH 444 source) can be explained with a variable ejection velocity jet model. For explaining the present positions of the HH 444 knots, however, it is necessary to invoke a more complex ejection velocity history than a single-mode, periodic variability.
We study the internal structure of coronal mass ejections (CMEs) using wavelet analysis. We derive wavelet spectra, spatially integrated over regions of interest within LASCO C2 white-light coronographic images. These spectra show an inflection point, which we use to characterize each spectrum. In a diagram of flux vs. spatial scale of the inflection point, we find that the analyzed structures fall into two, distinct groups: a lowflux, small-spatial-scale group (which we call the "homogeneous" type), and a high-flux, larger-spatial-scale group (the "collimated" type). Interestingly, if we study different regions of a given image, all of the structures fall into one of the two groups described above. From a qualitative comparison with the images, it is clear that the two groups identified by the wavelet analysis correspond to two types of morphologies, which are seen as either more-homogeneous or more-collimated structures.
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