Browsing by Author "Keel, William"

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    Signatures of feedback in the spectacular extended emission region of NGC 5972
    (2023) Harvey, Thomas; Maksym, W. Peter; Keel, William; Koss, Michael; Bennert, Vardha N.; Chojnowski, S. Drew; Treister, Ezequiel; Finlez, Carolina; Lintott, Chris J.; Moiseev, Alexei; Simmons, Brooke D.; Sartori, Lia F.; Urry, Megan
    We present Chandra X-ray Observatory observations and Space Telescope Imaging Spectrograph spectra of NGC 5972, one of the 19 ‘Voorwerpjes’ galaxies. This galaxy contains an extended emission-line region (EELR) and an arcsecond scale nuclear bubble. NGC 5972 is a faded active galactic nucleus (AGN), with EELR luminosity suggesting a 2.1 dex decrease in Lbol in the last ∼5 × 104 yr. We investigate the role of AGN feedback in exciting the EELR and bubble given the long-term variability and potential accretion state changes. We detect broad-band (0.3–8 keV) X-ray emission in the near-nuclear regions, coincident with the [O III] bubble, as well as diffuse soft X-ray emission coincident with the EELR. The soft nuclear (0.5–1.5 keV) emission is spatially extended and the spectra are consistent with two APEC thermal populations (∼0.80 and ∼0.10 keV). We find a bubble age >2.2 Myr, suggesting formation before the current variability. We find evidence for efficient feedback with Pkin/Lbol ∼ 0.8 per cent, which may be overestimated given the recent Lbol variation. [O III] kinematics show a 300 km s−1 high-ionization velocity consistent with disturbed rotation or potentially the line-of-sight component of a ∼780 km s−1 thermal X-ray outflow capable of driving strong shocks to photoionize the precursor material. We explore possibilities to explain the overall jet, radio lobe and EELR misalignment including evidence for a double supermassive black hole which could support a complex misaligned system.