Measurement of the Full Shape of the Thermal Sunyaev-Zeldovich Power Spectrum from South Pole Telescope and {\it Herschel}-SPIRE Observations

Abstract

We present a measurement of the full shape of the power spectrum of the thermal Sunyaev-Zeldovich (tSZ) effect down to arcminute scales using cosmic microwave background (CMB) data from the South Pole Telescope (SPT) over roughly 100 ${\rm deg}^{2}$ field. The analysis incorporates data from the 2019/20 seasons of the SPT-3G survey in bands centered at 95, 150, and 220 GHz; from the full SPTpol dataset at 150 GHz; and from {\it Herschel}-SPIRE survey in bands centered at 600 and 857 GHz. We combine data from all the above bands using linear combination (LC) techniques to produce a tSZ or Compton-$y$ map. We modify the LC weights to produce multiple versions of the Compton-$y$ map, including minimum-variance (MV) and foreground-minimized (-min) maps. We measure the auto- and cross-spectra of a subset of these maps in the range $\ell \in [500, 5000]$. While this power spectrum includes contributions from signals other than tSZ, we present numerous checks to show that the most challenging foreground signal, the cosmic infrared background (CIB) is much lower than the desired tSZ signal in the scales of interest in this work. The final tSZ power spectrum is measured at $9.3\sigma$ with both the MV and CIB-min maps. Our results are consistent with those reported in other CMB surveys across the literature. Using the difference in the tSZ power spectrum from MV and CIB-min maps, we reconstruct the scale-dependent tSZ-CIB cross-correlation $\rho_{\ell}^{\rm tSZ \times CIB}$, finding $3.1\sigma$ evidence for a nonzero correlation coefficient that is positive on large scales and approaches zero for $\ell > 2500$. This result represents the deepest tSZ maps ever produced and provides new constraints that can help refine astrophysical feedback mechanisms and models of the intracluster medium.