New results on particle acceleration in the Centaurus A jet and counterjet from a deep Chandra observation

TL;DR

This study uses deep Chandra X-ray observations to analyze particle acceleration mechanisms in the Centaurus A jet and counterjet, revealing different regimes of acceleration and evidence of diffuse processes.

Contribution

It provides detailed spectral measurements along the jet and identifies a likely distributed acceleration mechanism in the outer regions, including the counterjet.

Findings

Inner jet dominated by shock acceleration at knots

Outer jet likely involves unknown distributed acceleration

Counterjet shows extended emission indicating diffuse acceleration

Abstract

We present new deep Chandra observations of the Centaurus A jet, with a combined on-source exposure time of 719 ks. These data allow detailed X-ray spectral measurements to be made along the jet out to its disappearance at 4.5 kpc from the nucleus. We distinguish several regimes of high-energy particle acceleration: while the inner part of the jet is dominated by knots and has properties consistent with local particle acceleration at shocks, the particle acceleration in the outer 3.4 kpc of the jet is likely to be dominated by an unknown distributed acceleration mechanism. In addition to several compact counterjet features we detect probable extended emission from a counterjet out to 2.0 kpc from the nucleus, and argue that this implies that the diffuse acceleration process operates in the counterjet as well. A preliminary search for X-ray variability finds no jet knots with dramatic flux density variations, unlike the situation seen in M87.