Imaging the Circumnuclear Region of NGC 1365 with Chandra

We present the first Chandra/ACIS imaging study of the circumnuclear region of the nearby Seyfert galaxy NGC 1365. The X-ray emission is resolved into point-like sources and complex, extended emission. The X-ray morphology of the extended emission shows a biconical soft X-ray emission region extending ~5 kpc in projection from the nucleus, coincident with the high excitation outflow cones seen in optical emission lines particularly to the northwest. Harder X-ray emission is detected from a kpc-diameter circumnuclear ring, coincident with the star-forming ring prominent in the Spitzer mid-infrared images; this X-ray emission is partially obscured by the central dust lane of NGC 1365. Spectral fitting of spatially separated components indicates a thermal plasma origin for the soft extended X-ray emission (kT=0.57 keV). Only a small amount of this emission can be due to photoionization by the nuclear source. Detailed comparison with [OIII]5007 observations shows the hot interstellar medium (ISM) is spatially anticorrelated with the [OIII] emitting clouds and has thermal pressures comparable to those of the [OIII] medium, suggesting that the hot ISM acts as a confining medium for the cooler photoionized clouds. The abundance ratios of the hot ISM are fully consistent with the theoretical values for enrichment from Type II supernovae, suggesting that the hot ISM is a wind from the starburst circumnuclear ring. X-ray emission from a ~450 pc long nuclear radio jet is also detected to the southeast.

💡 Research Summary

This paper presents the first high‑resolution Chandra/ACIS imaging study of the circumnuclear region of the nearby Seyfert galaxy NGC 1365. Using a total exposure of ~100 ks, the authors separate the X‑ray emission into three distinct components: (1) a compact, hard point source coincident with the active nucleus; (2) a biconical soft‑X‑ray structure extending roughly 5 kpc on either side of the nucleus; and (3) a hard‑X‑ray emitting, kiloparsec‑scale circumnuclear ring that matches the star‑forming ring seen in Spitzer mid‑infrared images.

The soft bicone aligns closely with the high‑excitation optical outflow cones traced by