Deep Chandra Observation of the Remarkable Ionization Cones of NGC 5252

Abstract

Seyfert galaxy NGC 5252 harbors enormously extended ionization cones, which have been previously detected in the optical and X-ray band, offering a unique opportunity to investigate the interaction between the central active galactic nucleus (AGN) and the surrounding gas in the AGN host galaxy. We present deep Chandra imaging spectroscopy of NGC 5252 with a total exposure time of 230 ks. The morphology in the soft X-rays shows resolved extended structure from nucleus to a large radial distance, and for the first time we detect the outermost X-ray arc at $\sim$20 kpc. The X-ray cone mostly follows the direction of the optical ionization cones in the southeast and northwest direction, about 20 degrees misaligned with the major axis of the galactic disk of NGC 5252. Fitting the spectra extracted from radial sectors with photoionization models supports that extended emission is mainly photoionized by the central AGN. We also examine the variation of the photoionization parameter along the radial extension, and infer a decreasing ionizing continuum of the central engine by a factor of $\sim$50 over the past 64000 years. These findings are consistent with previous suggestion that NGC 5252 resembles a quasar relic with a $M\sim 10^9 M_{\odot}$ supermassive black hole, which went through a minor merger event and switched to a low accretion rate state.