# Intensity Mapping in the Presence of Foregrounds and Correlated Continuum Emission

## TL;DR

This paper discusses methods for separating line emission from foreground and continuum contamination in intensity mapping surveys, with a focus on cross-correlation techniques and future multi-band survey capabilities.

## Contribution

It introduces a joint estimation approach for correlated continuum emission and foreground cleaning, applied to Planck and BOSS data for high-redshift CII detection.

## Key findings

- Effective separation of line and continuum emission in cross-correlation.
- Challenges of foreground contamination in low-band surveys.
- Potential of multi-band surveys to improve emission separation.

## Abstract

Intensity mapping has attracted significant interest as an approach to measure the properties of the interstellar medium in typical galaxies at high redshift. Intensity mapping measures the statistics of surface brightness as a function of frequency, making it sensitive not only to all line emission of interest but also radiation from all other sources. Significant effort has gone into developing approaches that reject foreground contamination. Additionally, the target galaxies have multiple sources of emission that can complicate the interpretation of the line brightness. We describe the problem of jointly estimating correlated continuum emission and cleaning uncorrelated continuum emission, such as from the Milky Way. We apply these considerations to a cross-correlation of Planck data with BOSS quasars for a determination of CII for 2 < z < 3.2. Intensity mapping surveys with few bands have unique challenges for treating foregrounds and avoiding bias from correlated continuum emission. We show how a future intensity mapping survey with many bands can separate line from continuum emission in cross-correlation.