23 NOVEMBRE 2021 ore 15:00

Cold gas sustaining the duty cycle of nearby AGNs

Dr. Filippo Maccagni (ASTRON, Paesi Bassi)
Cold gas sustaining the duty cycle of nearby AGNs

The recent MeerKAT deep surveys o the nearby Universe (e.g. MeerKAT Fornax Survey and Mhongoose) opened a new era of investigation of neutral atomic (HI) gas studies in nearby galaxies. Now, we are enabled  to study low-column density (<5x10^19 cm^-2) HI in all types of galaxies in different environments, from isolated objects to groups and clusters. For example, observing low-column density HI from the macro (hundreds of kpc) to the micro scale (a few kpc) in active galactic nuclei (AGNs) allows us to identify and trace not only signatures of AGN-feedback (i.e. gaseous outflows) but also phenomena of cold gas accretion. 

In this talk, I will show how using also the high spatial resolution observation of the radio continuum emission of AGNs, we can connect the presence of HI in the centre with the history of the nuclear activity occurred in the galaxy. I will present recent deep HI observations (<5x10^19 cm^-2)  from the Australia Telescope Compact Array and different MeerKAT projects of nearby radio AGNs (<100 Mpc), which allowed us to shed new light on the role of cold gas in radio AGNs. By integrating, when needed, with information on the molecular and ionised gas (from ALMA and MUSE observations), I will focus on the impact of AGNs on the surrounding interstellar medium and which mechanisms regulate their life-cycle, for example, between ‘external’ phenomena (i.e. mergers and interactions) with ‘internal’ phenomena (i.e. cold chaotic accretion, secular events). For some sources, I will highlight the crucial synergy between not only radio but also multi-wavelength spatially resolved spectral line observations to better understand the mechanisms of gas accretion in AGNs.



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