Detection of the CMB lensing – galaxy bispectrum
November 7, 2023·
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1 min read
Gerrit S. Farren
Blake D. Sherwin
Boris Bolliet
Toshiya Namikawa
et al.
Abstract
We present a first measurement of the galaxy–galaxy–CMB-lensing bispectrum. The signal is detected at $26\sigma$ and $22\sigma$ 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.
Type
Publication
Submitted to Physical Review Letters
A first detection of the three-point cross-correlation between CMB lensing and galaxies, opening a new non-Gaussian probe of large-scale structure beyond what two-point analyses can access. See the unWISE × ACT DR6 CMB lensing project for context.
Authors
Gerrit S. Farren
(he/him)
Cosmologist & Data Scientist | Mapping the Universe at Scale
Cosmologist working on multi-probe analyses of the largest cosmological datasets. I build large scale analysis pipelines that combine Bayesian inference, distributed/HPC computing, and careful systematics control to turn modern survey data into robust physical insight.