February 2-5, 2021

Oral Presentation

NuSTAR Non-detection of a Faint Active Galactic Nucleus in an Ultraluminous IR Galaxy with Kpc-scale Fast Wind

Author(s): Xiaoyang Chen (NAOJ), Kohei Ichikawa (Tohoku Univ.), Hirofumi Noda (Osaka Univ.), Taiki Kawamuro (NAOJ), Toshihiro Kawaguchi (Onomichi City Univ.), Yoshiki Toba (Kyoto Univ.), and Masayuki Akiyama (Tohoku Univ.)

Presenter: Xiaoyang Chen (NAOJ)

Large-scale outflows are generally considered as a possible evidence that active galactic nuclei (AGNs) can severely affect their host galaxies. Recently an ultraluminous IR galaxy (ULIRG) at z=0.49, AKARI J0916248+073034, was found to have a galaxy-scale [OIII] 5007 outflow with one of the highest energy-ejection rates at z<1.6. However, the central AGN activity estimated from its torus mid-IR (MIR) radiation is weak relative to the luminous [OIII] emission. In this work we report the first NuSTAR hard X-ray follow-up of this ULIRG to constrain its current AGN luminosity. The intrinsic 2-10 keV luminosity shows a 90% upper-limit of 3.0*10^43 erg s-1 assuming Compton-thick obscuration (nH=1.5*10^24 cm-2), which is only 3.6% of the luminosity expected from the extinction corrected [OIII] luminosity. With the NuSTAR observation, we succeed to identify that this ULIRG has a most extreme case of X-ray deficit among local ULIRGs. A possible scenario to explain the drastic declining in both of the corona (X-ray) and torus (MIR) is that the primary radiation from the AGN accretion disk is currently in a fading status, as a consequence of a powerful nuclear wind suggested by its powerful ionized outflow in the galaxy scale.

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