报告题目：The electron pressure profile from SZ cluster stacks: mass and redshift dependence

　　报 告 人：Dr. Denis Tramonte

　　报告人简介：Dr. Denis Tramonte obtained his PhD from the Canary Islands Institute of Astrophysics (IAC, Spain) in 2017. He later joined the University of KwaZulu-Natal (UKZN, South Africa) as a Claude Leon Postdoctoral fellow. Since January 2021 he is a PIFI Postdoctoral fellow at the Purple Mountain Observatory (PMO) working in the SKA Cosmology group led by Prof. Yin-Zhe Ma. His main research topic is the observational study of the large scale structure in the Universe, with particular focus on the cosmic web nodes and filaments, using existing observations of both neutral baryons (via the HI 21-cm line) and ionised baryons (via the Sunyaev-Zel'dovich effect) in combination with object tracers of the cosmic web (cluster catalogues and galaxy catalogues obtained from observations at different wavelengths). In parallel, he is working on the study of the Galactic emission in both intensity and polarisation in the framework of CMB foreground science, specifically using data from the QUIJOTE experiment (Tenerife, Spain).

　　摘 要：In this talk I will present my work related to the study of the electron pressure profile in the intra-cluster medium (ICM) of galaxy clusters. Being the largest virialised structures observable in our Universe, galaxy clusters encode a wealth of information on the processes of structure formation and galaxy evolution. The quantity most directly related to theory, i.e. the cluster mass, is not directly observable; cluster masses are obtained by defining some observable "mass proxies" which can be converted into the mass via suitable scaling relations. As the ICM is ionised, mass proxies have been defined from observations of both X-ray emission and (more recently) the Sunyaev-Zel'dovich (SZ) effect. Previous studies based on a limited number of resolved clusters agreed in describing the radial electron pressure profile in clusters via a universal parametrisation which factorises out the mass and redshift dependence. In our work we test this prediction on a large population (~37,000) of galaxy clusters obtained by merging pre-existing cluster catalogues. We stack the clusters on maps of the SZ Compton-y parameter obtained from both the Planck satellite and the Atacama Cosmology Telescope (ACT), and extract an effective radial Compton-y profile. The latter can be predicted theoretically with a halo model which is parametrised in terms of the universal pressure profile; we then employ MCMC methods to obtain independent estimates on the intervening parameters. The large statistics available for our cluster sample allows us to split the sample into separate mass and redshift bins, thus enabling us to test possible deviations from universality in the pressure profile parametrisation. The results contribute to improve our understanding of the ionised medium in galaxy clusters, and of the associated mass proxies.

　　时 间：2021年11月5日星期五12:00

　　地 点：紫台3-402

欢迎大家参加！