The Hidden Mass and Large Spatial Extent of a Poststarburst Galaxy Outflow

TL;DR

This study reveals that poststarburst galaxy winds contain significantly more mass in warm-hot plasma than in cold gas, extend over large distances, and likely influence galaxy evolution through substantial mass removal.

Contribution

It provides observational evidence that warm-hot plasma dominates the mass in galaxy outflows and extends over large scales, highlighting the importance of multiphase winds in galaxy evolution.

Findings

Warm-hot plasma contains 10-150 times more mass than cold gas.

The wind extends beyond 68 kiloparsecs, with some material escaping.

Warm-hot plasma is linked to cold matter interacting with hotter phases.

Abstract

Outflowing winds of multiphase plasma have been proposed to regulate the buildup of galaxies, but key aspects of these outflows have not been probed with observations. Using ultraviolet absorption spectroscopy, we show that "warm-hot" plasma at 10^{5.5} K contains 10-150 times more mass than the cold gas in a poststarburst galaxy wind. This wind extends to distances >68 kiloparsecs, and at least some portion of it will escape. Moreover, the kinematical correlation of the cold and warm-hot phases indicates that the warm-hot plasma is related to the interaction of the cold matter with a hotter (unseen) phase at >>10^{6} K. Such multiphase winds can remove substantial masses and alter the evolution of poststarburst galaxies.