A geometric census of giants in the Local Universe: Bayesian inference of a sparse Paretian population

Metro Toronto Convention Centre 

The radio sky reveals that black hole jets carry electrons and magnetic fields far into the intergalactic medium. In exceptional cases, these outflows give individual galaxies an Mpc-scale sphere of influence. Such giant outflows, or simply giants, embody the most extreme known way in which galaxies affect the Cosmic Web. Despite this, the triggers of giant growth remain unknown. Here we use the LOFAR Two-metre Sky Survey (LoTSS) to measure giant growth's central geometric quantity: total length. We first formulate a statistical framework that is both rigorous and practical, and then search the LoTSS for giants, discovering 2060 previously unknown specimina. Spectacular findings include the longest giant overall, the longest hosted by a spiral galaxy, and 13 giants that appear larger in the sky than the Moon. By combining theory and data, we infer that giant lengths are Pareto distributed with tail index -3.5 ± 0.5. We also deduce the comoving number density of giants and their volume-filling fraction, both for the first time. We conclude that giants are truly rare: at any moment in time, most clusters and filaments — the building blocks of the Cosmic Web — do not harbour giants.