Revisiting the Circumnuclear X-Ray Emission of NGC 2992 in a Historically Low State

Abstract

The innermost region of the Seyfert galaxy NGC 2992 has long been suspected to be the location of intense AGN–host galaxy interaction, but photon pile up in previous high-resolution observations hampered the study of the soft X-ray excess and the interaction near its nucleus. We present an X-ray imaging and spectroscopic analysis of the circumnuclear (1″–3″) region of NGC 2992 using the zeroth-order image of a 135 ks grating observation obtained with Chandra, which captured the nucleus in a historically low flux state. Extended soft X-ray emission is detected in the circumnuclear region with an observed luminosity of L X ∼ 7 × 1039 erg s−1. The majority of the previous, puzzling detection of soft excess could be associated with the outflow, indicated by the morphological correspondences between the soft X-ray emission and figure-eight-shaped radio bubbles. An anomalous narrow emission line with a centroid energy of ∼4.97 keV is found. If attributed to redshifted highly ionized iron emission (e.g., Fe xxv), the required outflow velocity is ∼0.23 c. An alternative explanation is that this line emission could be produced by the nuclear spallation of iron. We also find extended, asymmetric Fe Kα emission along the galactic disk, which could originate from reflection by cold gas on ∼200 pc scale.