The Complex North Transition Region of Centaurus A: A Galactic Wind

TL;DR

Deep GALEX imaging reveals a complex, extended wind-driven weather system in Centaurus A, driven by starburst and AGN activity, interacting with merger remnants and producing diverse emission features.

Contribution

This study provides new multi-wavelength observations of Centaurus A's northern region, linking starburst and AGN winds to the observed weather phenomena and emission structures.

Findings

Detection of a 35 kpc long UV and Hα emission ribbon.

Evidence of a starburst activity at ~2 solar masses per year.

Wind interactions with merger remnants explain the complex emission features.

Abstract

We present deep GALEX images of NGC 5128, the parent galaxy of Centaurus A. We detect a striking "weather ribbon" of Far-UV and H$\alpha$ emission, which extends more than 35 kpc northeast of the galaxy. The ribbon is associated with a knotty ridge of radio/X-ray emission, and is an extension of the previously known string of optical emission-line filaments. Many phenomena in the region are too short-lived to have survived transit out from the inner galaxy; something must be driving them locally. We also detect Far-UV emission from the galaxy's central dust lane. Combining this with previous radio and Far-IR measurements, we infer an active starburst in the central galaxy, which is currently forming stars at $\sim 2 M_{sun}$yr$^{-1}$, and has been doing so for 50-100Myr. If the wind from this starburst is enhanced by energy and mass driven out from the AGN, the powerful augmented wind can be the driver needed for the northern weather system. We argue that both the diverse weather system, and the enhanced radio emission in the same region, result from the wind's encounter with cool gas left by one of the recent merger/encounter events in the history of NGC 5128.