The Sudden Death of the Nearest Quasar

TL;DR

This paper measures the rapid shutdown timescale of a nearby quasar, revealing a transition in black hole accretion physics within 70,000 years, which impacts our understanding of galaxy evolution.

Contribution

First direct measurement of a quasar shutdown timescale using X-ray observations, indicating a rapid transition in black hole accretion states.

Findings

Quasar in galaxy IC 2497 shut down within 70,000 years.

Black hole radiative output decreased by over 2-4 orders of magnitude.

Transition may involve a shift to a radiatively inefficient accretion state.

Abstract

Galaxy formation is significantly modulated by energy output from supermassive black holes at the centers of galaxies which grow in highly efficient luminous quasar phases. The timescale on which black holes transition into and out of such phases is, however, unknown. We present the first measurement of the shutdown timescale for an individual quasar using X-ray observations of the nearby galaxy IC 2497, which hosted a luminous quasar no more than 70,000 years ago that is still seen as a light echo in `Hanny's Voorwerp', but whose present-day radiative output is lower by at least 2 and more likely by over 4 orders of magnitude. This extremely rapid shutdown provides new insights into the physics of accretion in supermassive black holes, and may signal a transition of the accretion disk to a radiatively inefficient state.