Long-term fate of atomic gas in quenched post-merger remnants

Determine the long-term fate of the substantial atomic-hydrogen reservoirs in quenched post-merger remnants beyond approximately 1.8 Gyr after coalescence, including whether the observed atomic-gas deficit is temporary and whether replenishment processes restore the reservoir.

Background

The study finds that quenched post-merger galaxies remain deficient in atomic hydrogen relative to matched control galaxies, yet retain substantial reservoirs of approximately 1.3–1.5 × 10^9 solar masses even at late post-coalescence times. The analysis based on the mummi sample probes only up to roughly 1.8 Gyr after coalescence, so it does not establish what happens to this remaining gas at later times.

The authors note that the deficit could be temporary if atomic gas is continually replenished, potentially through cosmological accretion or merger-induced cooling. Resolving this issue is important for determining whether quenched merger remnants retain a long-lived fuel supply capable of supporting renewed star formation or disk re-formation.