Extended X-ray emission in the IC 2497-Hanny's Voorwerp system: energy injection in the gas around a fading AGN


We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN. We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN (L-bol similar to 10(42)-10(44) erg s(-1)). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN (E-bub similar to 10(54)-10(55) erg). A possible scenario is that this bubble is inflated by the fading AGN, which after changing accretion state is now in a kinetic mode. Other possibilities are that the bubble has been inflated by the past luminous quasar (L-bol similar to 10(46) erg s(-1)), or that the temperature gradient is an indication of a shock front from a superwind driven by the AGN. We discuss the possible scenarios and the implications for the AGN-host galaxy interaction, as well as an analogy between AGN and X-ray binaries lifecycles. We conclude that the AGN could inject mechanical energy into the host galaxy at the end of its lifecycle, and thus provide a source for mechanical feedback, in a similar way as observed for X-ray binaries.

galaxies: active, quasars: general, quasars: individual: IC 2497, X-rays: galaxies, ACTIVE GALACTIC NUCLEI, ACCRETING BLACK-HOLES, HANNYS VOORWERP, GALAXY ZOO, DOMINATED ACCRETION, BINARIES, QUASAR, EVENTS, GROWTH, STARBURSTS, Astronomy & Astrophysics
Sartori, L. et al. (2016): Extended X-ray emission in the IC 2497 – Hanny's Voorwerp system: energy injection in the gas around a fading AGN. Monthly Notices of the Royal Astronomical Society, 457(4). DOI: https://doi.org/10.1093/mnras/stw230