Thermal SZ effect in the CGM

The thermal Sunyaev-Zeldovich (SZ) Effect is the distortion in the cosmic microwave background (CMB) spectrum due to the inverse-Compton scattering of the CMB photons with the ionized intervening medium. The thermal SZ (tSZ) Effect is characterized by Compton-y, a measure of thermal pressure/thermal energy of hot halos, e.g., intracluster medium (ICM), intragroup medium (IGrM), and circumgalactic medium (CGM). To detect the weak tSZ signal from the CGM, one requires high angular resolution CMB data, and to stack on many (~100,000) galaxies together.

We cross-correlate the galaxy catalog of WISExDESI with the Compton-y map from Atacama Cosmology TelescopexPlanck to study the stacked tSZ signal in the CGM in light of the star formation. The dependence of thermal energy (or its upper limit) on halo mass is different for star-forming and quiescent galaxies. (Das, Truong, Chiang & Mathur, 2025 (in press)

We cross-correlate the galaxy catalog of WISExSuperCosmos with the Compton-y map from Atacama Cosmology Telescope x Planck for galaxies that are not [AGN, radio-bright, or in galaxy clusters] to measure the stacked tSZ signal in the CGM of our galaxies. The dependence of thermal energy and baryon fraction on mass is stronger than expected and is not monotonic. It implies that different types of galactic outflows/feedback are at play that we have yet to theoretically understand. (Das, Chiang & Mathur, 2023, ApJ, 951, 125)

We are now studying the redshift evolution of the tSZ effect. Stay tuned...

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