Misalignment between cold gas and stellar components in early-type galaxies

TL;DR

This study investigates the spatial offset between atomic hydrogen gas and stars in blue early-type galaxies, suggesting black hole feedback may rapidly quench star formation rather than gas exhaustion.

Contribution

It provides pilot observations showing gas-stellar offsets and nuclear activity, indicating feedback-driven star formation truncation in early-type galaxies.

Findings

Increasing gas-stellar offsets with galaxy age

Nuclear activity associated with gas displacement

Radio lobes aligned with displaced gas reservoirs

Abstract

Recent work suggests blue ellipticals form in mergers and migrate quickly from the blue cloud of star-forming galaxies to the red sequence of passively evolving galaxies, perhaps as a result of black hole feedback. Such rapid reddening of stellar populations implies that large gas reservoirs in the pre-merger star-forming pair must be depleted on short time scales. Here we present pilot observations of atomic hydrogen gas in four blue early-type galaxies that reveal increasing spatial offsets between the gas reservoirs and the stellar components of the galaxies, with advancing post-starburst age. Emission line spectra show associated nuclear activity in two of the merged galaxies, and in one case radio lobes aligned with the displaced gas reservoir. These early results suggest that a kinetic process (possibly feedback from black hole activity) is driving the quick truncation of star formation in these systems, rather than a simple exhaustion of gas supply.