Khagol Bulletin # 136 (Apr 2025) - ENG

| 08 | KHAG L | No. 136 - APRIL 2025 Top: Representation of the top two panels of Fig. 5 and 6 fromGirdhar et al. 2022 showing enhanced kinematics in ionised and molecular gas of J1316+1753, a prototype of multi- phase observation of jet-ISM interaction. Bottom: Representation of the middle panel of Fig. 8 of Meenakshi et al. 2022 showing predicted [OIII] emission and line widths (W80) from simulations of jet-ISM interaction, with enhanced widths perpendicular to the jet, as also observed inmulti-phase observations, such as top panel. of local impact of jet driven AGN feedback on the galaxy. The trapped jet shocks the ambient gas, driving multi-phase outflows and injecting turbulence. This results in strong disturbance to the gas kinematics, which has been confirmed from spatially resolved observations of jet-ISM interaction (see Figure 2). During the phase, although the jet's progress is slowed down, the forward shock keeps expanding as the jet's energy is redirected to other areas beyond the jet-beam. This results in the formation of a quasi- spherical energy bubble that sweeps through the ISM creating localised outflows and shocks. Such outflows regulate the gas content available within the host galaxy's potential that can form stars. Multiple episodes of AGN/jet activity are predicted to create a galactic fountain like scenario, where a fraction of gas is kept off-limits from the starformation process, though not completely escaping the galaxy's potential. The induced turbulence is expected to further add to the decline of starformation rate or at least, in reduction of the efficiency of starformation (Mandal et al. 2021). Beyond the confined phase, the jet breaks out of the dense gas (the “break- out” phase) and extends into the ambient low density background. For a duration beyond the break-out, the jet still keeps influencing the gas as the high pressured cocoon engulfs the ISM driving shocks and compressing the gas on scales beyond the immediate confines of the jet. From here- on, the un-hindered jet proceeds fast, with a more conical shaped forward shock (the “classical” phase). The simulations have been aptly supported by spatially observations of jet-ISM interactions. For some specific sources, detailed comparisons of qualitative predictions from the simulations have been made with the observed results, such as IC 5063 (Mukherjee et al. 2018a), 4C 31.04 (Zovaro et al. 2019), B2 0258+35 (Murthy et al. 2022), 2MASSX J23453269- 044925 (Nesvadba et al. 2021), Tea Cup galaxy (Audibert et al. 2023) etc. The ready access to large scale international observational facilities (e.g. VLT, ALMA, JWST etc.) with sufficient resolution to provide spatially resolved variation of gas kinematics through has revolutionised powerful radio jets are usually found in early type galaxies (ETG), which were considered to be gas poor. However, in the last decade, systematic surveys of such systems have uncovered a significant fraction (~34% Tadhunter et al. 2024) to have dense gas to the order of 107-107 M ⊙ . Radio-loud galaxy (RLG) fraction hosting dense gas has also been found to increase with red-shift (Audibert et al. 2022). Thus a significant fraction of RLG have dense gas and are expected to undergo the feedback processes outlined above. Another point disfavouring the role of jets was the low fraction of RLG in earlier galaxy surveys (~10-30%), indicating the radio loud phase comprises a small fraction of galactic lifetimes. However, again, recent deeper surveys by advanced instruments such as LOFAR has changed this, and find a higher fraction of such sources in general, with all galaxies showing some level of radio-AGN activity at lower luminosities (Sabater et al. 2019). However, in spite of these advances, this field is still yet to fully mature. Most observational and even simulations provide a single snapshot of the galaxy during its evolutionary course. The long term impact of such activities both on the evolution of the gas and stars is not well studied both in observations and theory. such studies. Although initially such studies had been confined to a few selected sources for observational convenience, large scale surveys have been initiated in recent years such as QSFeedS (Jarvis et al. 2021), QSOFEED (Ramos Almeida et al. 2022), GATOS (Garcia-Burillo et al. 2021), to identify the influence of the AGN in general and the radio jet in particular on their hosts. For a more detailed list of such observational efforts the reader is referred to the recent reviewbyMukherjee 2025. Thus the combined efforts of simulations and obs e r v a t i ons ha v e s t r ong l y established that jet driven local feedback can strongly influence the host galaxy, confirming the dual role of jets in the AGN feedback scenario. While jets are essential to drive the large scale radio/maintenance mode feedback to offset cooling flows, they also contribute to the quasar / establishment mode by affecting the local ISM, which has hitherto been neglected. This is in contrast to earlier general skepticism of the local impact of jets. However, such perceptions are starting to change. One of the major concerns of the role of jets on their host galaxy was whether they have enough gas in the first place to be affected by jets. The traditional view has been that in the nearby universe,