AGN on the Beach

Duty cycle

Radio observations of nearby X-ray and optically bright giant elliptical galaxies and their interaction with the intergalactic medium

Romana Grossova

 We, 11:50 ! Livein  Palazzo Santa Chiarafor  15min

Many massive early-type galaxies host central radio sources and hot X-ray atmospheres indicating the presence of radio-mechanical AGN feedback. The duty cycle and detailed physics of the radio-mode AGN feedback is still a matter of debate. To address these questions, we analyzed 1-2 GHz JVLA radio observations of a sample of the 42 nearest optically and X-ray brightest early-type galaxies. We detect radio emission in 41/42 galaxies. Furthermore, 27/42 galaxies in our sample host extended radio structures and 34/42 sources show environmental interactions in the form of X-ray cavities. We find a significant correlation between the radio flux density and the largest linear size of the radio emission and between the radio power and the luminosity of the central X-ray point-source. The central radio spectral indices of the galaxies span a wide range of values, with the majority of the systems having steep spectra and the rest flat spectra. These results are consistent with AGN activity, where the central radio sources are mostly switched on, thus the duty cycle is very high. For the future, we plan to investigate the cold gas content in our sample with ALMA, to understand in more depth the feeding process of the central engine.

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