The Chandra HRC View of the Sub-arcsecond Structures in the Nuclear Region of NGC 1068

TL;DR

This study uses high-resolution Chandra X-ray imaging to resolve sub-arcsecond structures in NGC 1068's nucleus, revealing detailed interactions between the radio jet and surrounding clouds, and identifying shock-heated regions.

Contribution

First high-resolution X-ray imaging of NGC 1068's nucleus that correlates X-ray, optical, and radio features to study jet-cloud interactions.

Findings

Resolved X-ray emission clumps matching optical clouds.

Identified locations of jet-cloud interactions.

Detected shock-heated regions with collisionally ionized gas.

Abstract

We have obtained a high spatial resolution X-ray image of the nucleus of NGC 1068 using the High Resolution Camera (HRC-I) on board the Chandra X-ray Observatory, which provides an unprecedented view of the innermost 1 arcsecond radius region of this galaxy. The HRC image resolves the narrow line region into X-ray emission clumps matching bright emission-line clouds in the HST [OIII]5007 images and allows comparison with sub-arcsecond scale radio jet for the first time. Two distinct X-ray knots are revealed at 1.3-1.4 arcsecond northeast and southwest of the nucleus. Based on the combined X-ray, [OIII], and radio continuum morphology, we identify the locations of intense radio jet-cloud interaction. The [OIII] to soft X-ray ratios show that some of these clouds are strongly affected by shock heating, whereas in other locations the jet simply thrusts through with no signs of strong interaction. This is further strengthened by the presence of a kT~1 keV collisionally ionized component in the ACIS spectrum of a shock heated cloud (HST-G). We estimate that the kinematic luminosity of the jet-driven shocks is 6x10^{38} erg/s, a negligible fraction (10^{-4}) of the estimated total jet power.