CMB lensing and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Ly</mml:mi><mml:mi>α</mml:mi></mml:math> forest cross bispectrum from DESI’s first-year quasar sample

Abstract

The squeezed cross-bispectrum ${B}_{\ensuremath{\kappa},\mathrm{Ly}\ensuremath{\alpha}}$ between the gravitational lensing in the cosmic microwave background and the 1D $\mathrm{Ly}\ensuremath{\alpha}$ forest power spectrum can constrain bias parameters and break degeneracies between ${\ensuremath{\sigma}}_{8}$ and other cosmological parameters. We detect ${B}_{\ensuremath{\kappa},\mathrm{Ly}\ensuremath{\alpha}}$ with $4.8\ensuremath{\sigma}$ significance at an effective redshift ${z}_{\mathrm{eff}}=2.4$ using Planck PR3 lensing map and over 280,000 quasar spectra from the Dark Energy Spectroscopic Instrument's first-year data. We test our measurement against metal contamination and foregrounds such as Galactic extinction and clusters of galaxies by deprojecting the thermal Sunyaev-Zeldovich effect. We compare our results to a tree-level perturbation theory calculation and find reasonable agreement between the model and measurement.