Detection of the Galaxy--Galaxy--Temperature Skewed Bispectrum

Abstract

We present the first measurement of the galaxy--galaxy--temperature skewed bispectrum, obtained by cross-correlating the squared, filtered unWISE galaxy overdensity with \textit{Planck} maps at 100, 143, 217, and 353~GHz. The signal is detected with high significance in all four channels. Its frequency dependence reveals contributions from hot gas through the thermal Sunyaev--Zel'dovich (tSZ) effect and from dust through the cosmic infrared background (CIB). With the galaxy occupation fixed, our halo-model fits favor higher integrated pressure and peak star-formation efficiency for the galaxy--temperature cross-spectra than for the skewed bispectrum. Comparisons with component-separated tSZ and CIB maps from the same \textit{Planck} observations indicate that this mismatch is not confined to the frequency-map fits. This difference motivates testing more flexible descriptions of gas pressure, CIB emission, and galaxy occupation. In particular, it could point to a mass dependence of the gas-pressure profile that our model does not fully capture. By giving greater weight to massive halos that host many galaxy pairs, the skewed bispectrum provides a complementary test of these descriptions, using information beyond two-point statistics at a comparable computational cost.