Deep Chandra Observations of NGC 5728. III: Probing the High-Resolution X-ray Morphology and Multiphase ISM Interactions in the Circumnuclear Region

TL;DR

This study uses high-resolution Chandra X-ray observations to analyze the complex X-ray morphology and interactions of the multiphase interstellar medium in the circumnuclear region of NGC 5728, revealing detailed gas properties and structures.

Contribution

It provides the first detailed high-resolution X-ray imaging analysis of NGC 5728's circumnuclear region, linking X-ray features with molecular gas and star formation structures.

Findings

Localized variations in X-ray absorption and emission processes.

Detection of hot gas associated with the star-forming ring.

Identification of potential X-ray binaries near the star-forming region.

Abstract

We present a detailed imaging analysis of 260 ks of sub-arcsecond resolution Chandra Advanced CCD Imaging Spectrometer (ACIS-S) observations of the nearby Seyfert 2 galaxy NGC 5728. Our study focuses on the bright and diffuse soft X-ray emission within the galaxy's inner ~1 kpc. By comparing the X-ray emission across different energy bands, we identify localized variations in the absorbing column and emission processes. We observe more X-ray absorption in the direction perpendicular to the bicone, which is co-located with an inner warped CO disk in the galaxy. The innermost region, which shows the strongest excess of hard X-ray emission, is spatially coincident with the CO(2-1) emission from ALMA and dusty spirals observed in a Hubble Space Telescope V-H color map. We detect soft extended emission associated with the circumnuclear star-forming ring at ~1 kpc, suggestive of hot gas with kT=0.44 keV. We derive measurements for the hot gas mass, M=7.9x10^5 solar masses, pressure, p=2.0x10^-10 dyne per square cm, and cooling times, t=193.2 Myr. In the vicinity of the star-forming ring, we detect two X-ray point sources with soft X-ray spectra and 0.3-7 keV luminosities L~8x10^38 erg per second. These properties suggest X-ray binaries.