Parsec-scale shocks in the kiloparsec-scale jet of Centaurus A

TL;DR

This study uses high-resolution VLBI observations of Centaurus A to identify compact shock regions in its kpc-scale jet, supporting the idea that stellar objects or gas clouds cause localized shocks, with implications for jet-interacting objects.

Contribution

First high-resolution VLBI imaging of Centaurus A's kpc-scale jet revealing compact shock regions associated with stationary features and X-ray emission, refining models of jet interactions.

Findings

Detected compact synchrotron emission regions coinciding with stationary features.

Resolved shock regions are only a few parsecs in extent, reducing the mass of intercepting objects.

Results support the hypothesis that stellar objects or gas clouds cause jet shocks.

Abstract

High angular resolution VLBI observations of Centaurus A have been undertaken that allow access to a wide field-of-view, encompassing both the well-studied pc-scale jet and the inner part of the kpc-scale jet. The VLBI observations have detected compact regions of synchrotron emission in the kpc-scale jet that coincide with three stationary features identified from previous VLA monitoring observations. Each of these stationary features is associated with strong localised X-ray emission. The VLBI results strengthen arguments made by previous authors suggesting that the stationary features may be the result of stellar objects or gas clouds traversing the jet flow, intercepting the jet and causing strong shocks. The VLBI data show that the most strongly shocked regions in these features are resolved but have extents no larger than a few pc, reducing the required mass of the typical intercepting object by a factor of ~10 relative to previous estimates, making explanations based on high mass loss stars or low density gas clouds more plausible.