Luck of the Irish? A companion of the Cloverleaf connected by a bridge of molecular gas

TL;DR

This study uses deep CO(3-2) observations of a high-redshift lensed quasar to reveal a interacting companion galaxy connected by a gas bridge, providing insights into galaxy mergers and quasar activity.

Contribution

It reports the discovery of a gas-rich companion galaxy connected by a molecular gas bridge to the Cloverleaf quasar, highlighting the role of mergers in galaxy evolution.

Findings

Discovery of a less massive companion galaxy 33 kpc away

Detection of a molecular gas bridge indicating interaction

Evidence of fast molecular gas possibly from outflows

Abstract

We present deep observations of CO(3-2) from the Cloverleaf lensed quasar-starburst at $z=2.56$. We discover a 4-5 times less massive companion at a projected distance of 33 kpc from the Cloverleaf host galaxy. The galaxies are connected by a bridge of CO emission, indicating that they are interacting and that the companion is being stripped by the Cloverleaf. We also find evidence for fast molecular gas in the spectral line of the Cloverleaf that may be an outflow induced by stellar or quasar feedback. All of these features may be ubiquitous among quasars and only detected here with the help of gravitational lensing and the sensitivity of the data. Overall, these findings agree with galaxy formation scenarios that predict gas-rich mergers play a key role in quasar triggering, starburst triggering and the formation of compact spheroids.