Forecasting the cross correlation of Terahertz Intensity Mapper [CII] line intensity maps with Euclid galaxies

TL;DR

This paper forecasts that the cross-correlation between Terahertz Intensity Mapper [CII] line intensity maps and Euclid galaxies will be detectable with high confidence, enabling constraints on cosmic [CII] intensity and galaxy contributions.

Contribution

It introduces a forecast for detecting the [CII]-galaxy cross-power spectrum using TIM and Euclid data, highlighting the potential to study cosmic [CII] emission history.

Findings

Cross-power spectrum detectable at >7σ confidence.

Poisson component detectable at >3σ in multiple bins.

Constraints on mean [CII] intensity over cosmic history.

Abstract

We forecast that the Terahertz Intensity Mapper (TIM) cross-correlated with Euclid's Fornax deep field (EDF-F), TIM$\times$EDF-F, will detect the [CII]-galaxy cross-power spectrum at a median redshift of 1.1 with $\gtrsim 7 \sigma$ confidence. The Poisson component of the cross-power spectrum at $0.1 \leq k \leq 10$ hMpc$^{-1}$ (i.e. cross-shot noise) will be detected at $\gtrsim 3 \sigma$ in 4 bins spanning $0.5 < z< 1.7$. This measurement will constrain the mean [CII] specific intensity over half of cosmic history and assess the degree to which Euclid-selected galaxies account for the [CII] intensity observed by TIM. We find that TIM can detect the cross-power spectrum across a wide range of [CII] intensity models.