Detection of the CMB lensing — galaxy bispectrum

Kavli Affiliate: Toshiya Namikawa

| First 5 Authors: Gerrit S. Farren, Blake D. Sherwin, Boris Bolliet, Toshiya Namikawa, Simone Ferraro

| Summary:

We present a first measurement of the galaxy-galaxy-CMB lensing bispectrum.
The signal is detected at $26sigma$ and $22sigma$ significance using two
samples from the unWISE galaxy catalog at mean redshifts $bar{z}=0.6$ and
$1.1$ and lensing reconstructions from Planck PR4. We employ a compressed
bispectrum estimator based on the cross-correlation between the square of the
galaxy overdensity field and CMB lensing reconstructions. We present a series
of consistency tests to ensure the cosmological origin of our signal and rule
out potential foreground contamination. We compare our results to model
predictions from a halo model previously fit to only two-point spectra, finding
reasonable agreement when restricting our analysis to large scales. Such
measurements of the CMB lensing galaxy bispectrum will have several important
cosmological applications, including constraining the uncertain higher-order
bias parameters that currently limit lensing cross-correlation analyses.

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