AGN on the Beach

Duty cycle

Constraining the AGN duty cycle in the galaxy cluster MS 0735.6+7421

Nadia Biava

 We, 12:5 ! Livein  Palazzo Santa Chiarafor  15min

The galaxy cluster MS 0735.6+7421 hosts one of the most powerful jetted AGN known. The radio plasma ejected from the central AGN has displaced the intra-cluster medium, leaving two pairs of X-ray cavities, associated with different outbursts, and a weak shock front. In this talk, I will present new LOFAR observations, which high sensitivity and resolution (up to sub-arcsec resolution with international baselines), allowed to study this source in great details. At LOFAR frequency (144 MHz) the outer radio lobes are wider, perfectly filling the X-ray cavities. An intermediate lobe and its associated X-ray cavity were discovered, indicating the presence of a further phase of jet activity. Combining multi-frequency radio data and X-ray data, the duty cycle of the source and the AGN feedback were investigated. The radio spectra of the lobes is very steep even at 144 MHz, indicating the presence of old particles. In three phases of jet activity, the AGN was active for most of the time with only brief quiescent phases that ensured the repeated heating of the central gas. Energy budget estimates indicate that a source of additional pressure support is needed to sustain the bubbles against the pressure of the external medium.

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