Abstract
Abstract We report the detection in Chandra Advanced CCD Imaging Spectrometer archival data of an elongated soft (<3 keV) X-ray feature to the south of the Compton-thick active galactic nucleus (AGN) galaxy IC 2497, coincident with the emission-line feature known as Hanny’s Voorwerp. The data are consistent with the spatial correspondence between X-ray, optical emission-line, and radio features detected in nearby obscured AGNs (e.g., ESO 428-G014). The X-ray luminosity of the (0.3–3.0 keV) soft feature is ∼1.2 × 1040 erg s−1. We infer an [O iii]/soft-X-ray ratio in the range of ∼200, consistent with the highest values measured in some of the clouds of NGC 4151. Overall, given the uncertainties, Hanny’s Voorwerp appears to be a feature consistent with the ionization cone emission of nearby AGNs. We estimate an X-ray recombination time of ∼2 × 107 yr, longer than the [O iii] recombination time (∼8000 yr). This suggests that extended soft X-ray components may be a better diagnostic of overall long-term activity, while detection of an [O iii] HV would point to a time-limited activity burst.
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