Vol 12, No 9

The X-ray nature of the nucleus in Seyfert 2 galaxy NGC 7590

Xin-Wen Shu, Jun-Xian Wang, Teng Liu, Wei Zheng


Abstract We present the results 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-Newton observations show that the X-ray emission of NGC 7590 is dominated by an off-nuclear ultra-luminous X-ray source (ULX) and extended emissions from the host galaxy, and the nucleus is rather weak, likely hosting a Compton-thick AGN. Our recent Chandra observation of NGC 7590 enables us to effectively remove the X-ray contamination from the ULX and the extended component. The nuclear source remains undetected at the flux level of ~ 4×10−15 erg cm−2 s−1. Although not detected, the Chandra data give a 2–10 keV flux upper limit of ~ 6.1×10−15 erg cm−2 s−1 (at a 3σ level), a factor of three less than the XMM-Newton value, strongly supporting the Compton-thick nature of the nucleus. In addition, we detected five off-nuclear X-ray point sources within the galaxy’s D25 ellipse, all with 2 – 10 keV luminosity above 2×1038 erg s−1 (assuming the distance of NGC 7590). In particular, the ULX previously identified by ROSAT data is resolved by Chandra into two distinct X-ray sources. Our analysis highlights the importance of high spatial resolution images in discovering and studying ULXs.


Keywords galaxies: active — galaxies: individual (NGC 7590) — galaxies: nuclei — X-rays: galaxies

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