The jet and counterjet of 3C 270 (NGC 4261) viewed in the X-ray with Chandra

TL;DR

This study uses Chandra X-ray observations to analyze the jet and counterjet of 3C 270, revealing synchrotron emission, jet dynamics, and the impact on surrounding interstellar medium, suggesting recent activity has enhanced particle acceleration.

Contribution

First detailed X-ray analysis of both jet and counterjet in 3C 270, linking X-ray emission to synchrotron processes and jet activity history.

Findings

X-ray emission is synchrotron radiation from the jets.

The jet and counterjet have remarkably similar properties.

Approximately 20% of the interstellar medium mass has been displaced by the radio source.

Abstract

The radio source 3C 270, hosted by NGC 4261, is the brightest known example of counterjet X-ray emission from a low-power radio galaxy. We report on the X-ray emission of the jet and counterjet from 130 ks of Chandra data. We argue that the X-ray emission is synchrotron radiation and that the internal properties of the jet and counterjet are remarkably similar. We find a smooth connection in X-ray hardness and X-ray to radio ratio between the jet and one of the X-ray components within the core spectrum. We observe wedge-like depressions in diffuse X-ray surface brightness surrounding the jets, and interpret them as regions where an aged population of electrons provides pressure to balance the interstellar medium of NGC 4261. About 20% of the mass of the interstellar medium has been displaced by the radio source. Treating 3C 270 as a twin-jet system, we find an interesting agreement between the ratio of jet-to-counterjet length in X-rays and that expected if X-rays are observed over the distance that an outflow from the core would have traveled in ~6x10^4 yr. X-ray synchrotron loss times are shorter than this, and we suggest that most particle acceleration arises as a result of turbulence and dissipation in a stratified flow. We speculate that an episode of activity in the central engine beginning ~6x10^4 yr ago has led to an increased velocity shear. This has enhanced the ability of the jet plasma to accelerate electrons to X-ray-synchrotron-emitting energies, forming the X-ray jet and counterjet that we see today.