SEMINAR 2026
Mapping the Cosmic Web with Hot Gas: Multi-Wavelength Cross-Correlations with the Thermal Sunyaev-Zel’dovich Effect
| Speaker | Dr Ayodeji Ibitoye, Guangdong Technion – Israel Institute of Technology, Shantou, China |
| Date/Time | Wednesday, 25 Nov, 11am |
| Location | S11-02-07 Conference Room |
| Host | A/Prof Phil Chan / Dr Abel Yang |
Abstract
The thermal Sunyaev-Zel’dovich (tSZ) effect traces the pressure of hot ionised gas, which complements what galaxies and gravitational lensing reveal about the cosmic web. Cross-correlating the tSZ field with other tracers of large-scale structure therefore tests cosmological models and the physics of baryons at the same time. In this talk I review a programme of such measurements based on Planck and ACT Compton-y maps.
The first part covers cross-correlations with WISE infrared galaxies, detected at 21.8σ, and with the integrated Sachs-Wolfe (ISW) effect, detected at 3.6σ. I show how the ISW-tSZ signal constrains quintessence dark-energy models with thawing, tracker and scaling-freezing dynamics. I then discuss forecasts for HI intensity mapping with FAST and for Stage-IV/V surveys, including the calibration of the hydrostatic mass bias and its link to the σ8 tension.
The second part presents recent measurements that extend the approach to new tracers. Radio galaxies from the LOFAR Two-metre Sky Survey (LoTSS DR2) are cross-correlated with the Compton-y map at 11σ, giving an effective galaxy bias of about 2.1 at the sample median redshift and an effective hydrostatic mass calibration of 
. Tomographic cosmic shear from DECaLS DR8 is cross-correlated with the Compton-y maps at 15.0σ with Planck and 12.4σ with ACT, giving 
and 0.756 ± 0.033 respectively, with a thermal pressure amplitude consistent with the fiducial profile. I highlight the main systematics, including contamination by the cosmic infrared background and the degeneracy between pressure calibration and cosmology.
I close with future directions, including 21-cm tests of interacting dark-sector models with MeerKAT and the QiTai Telescope, and opportunities for collaboration.
Biography
I am currently a Research Fellow at the Guangdong Technion – Israel Institute of Technology, Shantou, China. Prior to that, I was an ANSO Fellow (postdoctoral scholar) at the National Astronomical Observatories, Chinese Academy of Sciences, Beijing. I earned a PhD in Cosmology from the University of KwaZulu-Natal, South Africa, in May 2021. I earned an MSc in Theoretical Physics (with Distinction) from the University of Ibadan, Nigeria, and a BSc (First Class) in Physics from Obafemi Awolowo University, Nigeria.
My research interest focuses on the cosmological exploitation of different large-scale structure observables, and also on 21 cm cosmology, to gain a better insight into the formation and evolution of cosmic structure in the Universe.
