NGC 5195 in M51: Feedback `Burps' after a Massive Meal?

TL;DR

This paper reports the discovery of double-arc X-ray structures in NGC 5195, interpreted as episodic outbursts from its central supermassive black hole, demonstrating large-scale feedback effects in the galaxy.

Contribution

It provides the first detailed observation of focused, episodic outflows from an SMBH in NGC 5195, illustrating feedback mechanisms in a nearby galaxy.

Findings

Double-arc X-ray structures are observed near NGC 5195's nucleus.

The arcs are likely caused by episodic SMBH outbursts.

Evidence of gas displacement and star formation in the arcs.

Abstract

We describe a double-arc-like X-ray structure lying ~15-30" (~0.8-1.7 kpc) south of the NGC 5195 nucleus visible in the merged exposures of long Chandra pointings of M51. The curvature and orientation of the arcs argues for a nuclear origin. The arcs are radially separated by ~15" (~1$ kpc), but are rotated relative to each other by ~30 deg. From an archival image, we find a slender Halpha-emitting region just outside the outer edge of the outer X-ray arc, suggesting that the X-ray-emitting gas plowed up and displaced the Halpha-emitting material from the galaxy core. Star formation may have commenced in that arc. Halpha emission is present at the inner arc, but appears more complex in structure. In contrast to an explosion expected to be azimuthally symmetric, the X-ray arcs suggest a focused outflow. We interpret the arcs as episodic outbursts from the central super-massive black hole (SMBH). We conclude that NGC 5195 represents the nearest galaxy exhibiting on-going, large-scale outflows of gas, in particular, two episodes of a focused outburst of the SMBH. The arcs represent a clear demonstration of feedback.