The X-ray Nature of Nucleus in Seyfert 2 Galaxy NGC 7590

TL;DR

This study uses high-resolution Chandra X-ray observations to investigate the nucleus of Seyfert 2 galaxy NGC 7590, revealing a likely Compton-thick AGN and resolving off-nuclear X-ray sources, emphasizing the importance of spatial resolution.

Contribution

First high-resolution Chandra imaging effectively isolates the galaxy's nucleus, confirming its Compton-thick nature and resolving ULXs previously blended in lower-resolution data.

Findings

Nucleus remains undetected at flux level ~4x10^{-15} erg/s/cm^2.

Chandra data constrains the nuclear flux to be less than 6.1x10^{-15} erg/s/cm^2.

ULX previously identified was resolved into two sources by Chandra.

Abstract

We present the result of the Chandra high-resolution observation of the Seyfert~2 galaxy NGC 7590. This object was reported to show no X-ray absorption in the low-spatial resolution ASCA data. The XMM observations show that the X-ray emission of NGC 7590 is dominated by an off-nuclear ultra-luminous X-ray source (ULX) and an extended emission from the host galaxy, and the nucleus is rather weak, likely hosting a Compton-thick AGN. Our recent Chandra observation of NGC 7590 enables to remove the X-ray contamination from the ULX and the extended component effectively. The nuclear source remains undetected at ~4x10^{-15} erg/s/cm^-2 flux level. Although not detected, Chandra data gives a 2--10 keV flux upper limit of ~6.1x10^{-15} erg/s/cm^-2 (at 3 sigma level), a factor of 3 less than the XMM value, strongly supporting the Compton-thick nature of the nucleus. In addition, we detected five off-nuclear X-ray point sources within the galaxy D25 ellipse, all with 2 -- 10 keV luminosity above 2x10^{38} erg/s (assuming the distance of NGC 7590). Particularly, the ULX previously identified by ROSAT data was resolved by Chandra into two distinct X-ray sources. Our analysis highlights the importance of high spatial resolution images in discovering and studying ULXs.