Investigating Galaxy Evolution and Active Galactic Nucleus Feedback with the Sunyaev-Zel'dovich Effect
Résumé
Galaxy formation is a complex process with aspects that are still very uncertain. A mechanism that has been used in simulations to successfully resolve several of these outstanding issues is active galactic nucleus (AGN) feedback, where a large amount of energy is driven outwards through a galaxy and the surrounding region by a central supermassive black hole. A promising method for directly measuring this energy is by looking at small increases in the energy of the cosmic microwave background (CMB) photons as they pass through hot gas, known as the thermal Sunyaev-Zel'dovich (tSZ) effect. I will present work done to measure the tSZ effect around a large number of 0.5 < z < 1.5 elliptical galaxies using the South Pole Telescope (SPT), Atacama Cosmology Telescope (ACT), and Planck telescope, finding signals at 1-sigma to 3-sigma confindence levels depending on the dataset and redshift range. The results are mixed, including hints at non-gravitational energy possibly due to AGN feedback. Then I will present work done to analyze these results further by comparing them to matching simulated measurements, both including and not including AGN feedback, from the large-scale Horizon-AGN and Horizon-NoAGN cosmological simulations. In these comparisons, the SPT results, which tend to have lower-mass galaxies (<5x10^11 M_Sun), favor the Horizon-AGN results at about a 1-sigma level, while the ACT results, which tend to have higher-mass galaxies (>5x10^11 M_Sun), favor the Horizon-NoAGN results at more than a 6-sigma level. These results indicate that AGN feedback may be milder than often predicted, and they also highlight the promising nature of tSZ effect measurements and the need for further work using better data and more varied simulations.