Nicole Thomas – The radio galaxy population in the SIMBA simulations

Thursday 13 May 2021

Nicole Thomas (UWC)

The radio galaxy population in the SIMBA simulations
Essentially all massive galaxies host a supermassive black hole (SMBH) at their centre. When these SMBHs become “active” they radiate energy across the electromagnetic spectrum and are identified as Active Galactic Nuclei (AGN). When observed at radio wavelengths, some of these AGN host relativistic jets that span up to hundreds of times the size of the host galaxy. These AGN, otherwise known as radio galaxies, are key contributors to the quenching of star formation in massive galaxies – though the mechanisms driving the accretion and feedback processes of these objects are still poorly understood and defined.
Observations show a dichotomy in the accretion efficiencies of radio galaxies which is thought to be the result of different fuelling mechanisms. With this hypothesis we present results from the SIMBA suite of cosmological simulations that is unique in that it employs a two-mode sub-resolution prescription for black hole accretion, namely, gravitational torque limited accretion from cold gas, and Bondi accretion from hot gas and accounts for the feedback from active galactic nuclei physically corresponding to observations. We identify a population of radio galaxies in SIMBA and separate them into populations of high and low excitation radio galaxies (HERGs and LERGs), study their global properties, and show that SIMBA provides a state-of-the-art cosmological context for understanding radio galaxies in the era of the Square Kilometer Array.

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