Insights into jet-induced cloud disruption in NGC 1316: ALMA reveals spatially extended molecular gas

We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(J = 1−0) observations of a nearby radio galaxy, NGC 1316, at 100 pc resolution to investigate the impact of active galactic nucleus (AGN) jets on the molecular gas. The molecular gas exhibits complex spatial and kinematic distributions, with broad CO line widths (>50 km s⁻¹) observed in several regions. The interferometric CO flux is only 34%–38% compared to single-dish data, indicating a large fraction of spatially extended molecular gas, especially in the central regions. We identified 24 giant molecular cloud associations (GMAs) primarily within the “NW Shell” and the “SE Blob”; these GMAs show velocity dispersions approximately twice as high as those in typical star-forming galaxies for their sizes. Analysis of archival ALMA CO(J = 2−1) and CO(J = 3−2) data reveals elevated line ratios (R₂₁ ∼ 1 and R₃₁ ∼ 1) in gas near the jet but, away from the jet, typical values (R₂₁ ∼ 0.7, R₃₁ ∼ 0.3). A multiwavelength comparison reveals a ∼5 kpc warm ionized gas shell that encompasses the molecular NW Shell. The observed energetics and bubble morphology are consistent with an expanding bubble model driven by the jet assuming a jet power of 1.6 × 10⁴³ erg s⁻¹. We propose that the high extended gas fraction results from the destruction of molecular clouds due to interactions with the jet plasma. NGC 1316 may be a good example of jet-induced negative feedback through the ablation, dispersal, and rarification of dense molecular clouds through jet–interstellar medium interactions.