Multi-tracer intensity mapping: cross-correlations, line noise & decorrelation

Line intensity mapping (LIM) is a rapidly emerging technique for constraining cosmology and galaxy formation using multi-frequency, low angular resolution maps. Many LIM applications crucially rely on cross-correlations of two line maps, or maps with surveys galaxy/CMB lensing. We present consistent halo model to predict all these enable joint analyses, in 3D redshift-space 2D projected extend the conditional luminosity function formalism multi-line case, consistently account correlated scatter between multiple luminosities. This allows us scale-dependent decorrelation key input foreground rejection approaches that estimate auto-spectra from cross-spectra. also enables reveal astrophysical properties interstellar medium inacessible auto-spectra. expose different sources "line noise" LIM, clarify their effects 1-halo shot noise terms. In particular, we show effective number density halos can some cases exceed galaxies, counterintuitively. Using observational simulation input, implement this H$\alpha$, [Oiii], Lyman-$\alpha$, CO [Cii] lines. encourage observers simulators measure correlation coefficients pairs lines whenever possible. Our code publicly available at https://github.com/EmmanuelSchaan/HaloGen/tree/LIM . companion paper, use highlight degeneracies astrophysics compare observables detection surveys.