Signatures of Inflowing Gas in Red Geyser Galaxies Hosting Radio Active Galactic Nuclei

Abstract

Abstract We study cool neutral gas traced by NaD absorption in 140 local (z < 0.1) early-type red geyser galaxies. These galaxies show unique signatures in spatially resolved strong line emission maps that have been interpreted as large-scale active galactic nucleus–driven ionized winds. To investigate the possible fuel source for these winds, we examine the abundance and kinematics of cool gas (T ∼ 100–1000 K) inferred from Na i D absorption in red geysers and matched control samples drawn from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey. We find that red geysers host greater amounts of NaD-associated material. Substantial cool gas components are detected in more than 50% of red geysers (compared to 25% of the control sample) going up to 78% for radio-detected red geysers. Our key result is that cool gas in red geysers is predominantly infalling. Among our 30 radio-detected red geysers, 86% show receding NaD absorption velocities (with respect to the systemic velocity) between 40 and 50 km s−1. We verify this result by stacking NaD profiles across each sample, which confirms the presence of infalling NaD velocities within red geysers (∼40 km s−1) with no velocity offsets detected in the control samples. Interpreting our observations as signatures of inflowing cool neutral clouds, we derive an approximate mass inflow rate of M ̇ in ∼ 0.1 M ⊙ yr − 1 , similar to that expected from minor merging and internal recycling. Some red geysers show much higher rates ( M ̇ in ∼ 5 M ⊙ yr − 1 ), which may indicate an ongoing accretion event.