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Determining Thermodynamic Properties of Cluster Gas Using Herschel-SPIRE

Presentation #512.06 in the session “Galaxy Clusters Observations”.

Published onJan 11, 2021
Determining Thermodynamic Properties of Cluster Gas Using Herschel-SPIRE

Galaxy clusters sit within one of the largest gravitational potential wells in the universe,creating environmental conditions not seen in other systems. Ongoing galaxy mergers, active galactic nuclei feedback, shock heating and other high-energy thermodynamic processes are common. Studying the thermal history of such systems sheds a light onto the evolution of the cluster gas and the processes that created it. One method to observe the temperature of the gas is through the Relativistic Sunyaev-Zeldovich Effect (rSZ), which is the relativistic boosting of Cosmic Microwave Background photons off of the hot intra-cluster gas via Inverse-Compton Scattering. The amplitude of this distortion is a direct measurement of the gas temperature, and is independent of the cluster redshift. This makes it an ideal counterpart to cluster X-ray measurements, which thus far outnumber significant detections of rSZ. It is also less sensitive to the density of the gas, making measurements of diffuse extended emission more viable. Despite these advantages, the rSZ spectrum is significantly impacted by far infrared dust emission, and requires careful characterization by alternate observations. The Planck satellite has made both robust detections of rSZ towards every cluster in our sample, as well as creating an all-sky dust map, but suffered from a large beam size. By combining low resolution Planck maps with more resolved Herschel -SPIRE data, the contaminating dust emission can be modelled independently of the SZ spectrum, providing a marked reduction in uncertainties of the measured gas temperature. This also allows the SPIRE temperature data to be compared with other data sets such as those of Chandra and XMM-Newton, which is the eventual goal of this project. I will be discussing the development of an analysis pipeline that will measure this effect in over 40 clusters using archival Herschel -SPIRE data.


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