The Sunyaev-Zel'dovich Effect as a Probe of the Thermodynamics of Extragalactic Systems
Crichton, Devin Thomas
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The thermal Sunyaev-Zel’dovich effect is a spectral distortion of the Cosmic Microwave Background that enables the study of the thermal state of ionized gasin extragalactic systems. The magnitude of this effect is proportional to the electron pressure distribution, and its integrated signal directly relates to the thermal energy of ionized gas. Additionally, as it does not suffer from cosmic surface brightness dimming, it enables observations out to arbitrarily high redshift. In this thesis, I present three studies which utilize this effect. In the first, I demonstrate a strong detection of the the average Sunyaev-Zel’dovich signal from radio selected galaxies, based on a statistical study of these systems. While these objects are thought to host powerful, accreting black holes whose associated jets could provide significant energetic input into the ionized halo gas, the results are consistent with expectations from purely gravitational heating. Conversely, in the second study, using a similar statistical analysis of optically selected radio-quiet quasars, I show evidence for a Sunyaev-Zel’dovich signal that is difficult to explain from purely gravitational arguments. The modeling favors a scenario in which much of the thermal energy originates from a coupling of the bolometric output of the luminous quasar emission to the ionized host halo, with an efficiency of ∼15%. Finally, in the third study, I evaluate the constraints on the radial distribution of the electron pressure in massive, Sunyaev-Zel’dovich selected galaxy clusters. Here I extract constraints on the average self-similar pressure profiles of these systems finding no strong evidence for evolution in their shape. However, an increase in intrinsic scatter around these best fit profiles, from ∼45% to 70–90% from z ∼0.37 to 0.67, is observed. This increase in intrinsic scatter has not previously been detected and indicates that non-gravitational processes could have an enhanced influence on these systems in earlier epochs of cosmic history.