When Jets Don't Quench: Near-Infrared H 2 in Star Forming Low-Excitation Radio Galaxies

We present new Gemini/GNIRS near-infrared spectroscopic observations of eight low-redshift (z < 0.1) blue low-excitation radio galaxies (BLERGs), a rare subset (about 2.5% of low-excitation radio galaxies; LERGs) that complicate the classical jet-mode AGN picture by combining radio activity with star-forming, gas-rich hosts. These star-forming BLERGs exhibit significant warm H 2 emission traced via ro-vibrational transitions at T about 2000 -- 4000 K. We find that BLERGs span a broad range of mass-normalized warm H 2 luminosities (L H 2/M), comparable to radio-emitting early-type galaxies, yet without a clear positive dependence on radio power. Instead, the strongest H 2 emission preferentially occurs in morphologically disturbed and advanced-merger systems, while compact radio sources (20 kpc) remain plausible sites of localized jet-ISM interaction. Together, these results suggest that merger-driven processes, including tidal shocks, gas inflows, and disturbed interstellar medium conditions, are the dominant drivers of warm molecular gas excitation in BLERGs, although localized jet-driven heating may contribute in individual systems. The compact radio morphologies, gas-rich hosts, and rarity of BLERGs are consistent with a short-lived evolutionary phase in which radio AGN activity coexists with an interaction-driven, molecular-rich interstellar medium prior to the onset of large-scale maintenance-mode feedback. Spatially resolved spectroscopy and higher-resolution radio imaging will be essential to disentangle the relative roles of mergers and jets in regulating the molecular gas of jet-mode AGN.