# A partial inventory of observational anisotropies in single-dish line-intensity mapping

## TL;DR

This paper investigates how observational anisotropies, caused by redshift-space distortions and instrumental effects, impact line-intensity mapping, and suggests that measuring the quadrupole can improve parameter constraints.

## Contribution

It explicitly models observational anisotropies in line-intensity mapping, highlighting the importance of quadrupole measurements for better cosmological parameter estimation.

## Key findings

- Instrumental resolution causes unavoidable signal loss.
- Measuring the quadrupole helps break parameter degeneracies.
- Anisotropies significantly affect the observed power spectrum.

## Abstract

Line-intensity mapping, being an imperfect observation of the line-intensity field in a cosmological volume, will be subject to various anisotropies introduced in observation. Existing literature in the context of CO and [C II] line-intensity mapping often predicts only the real-space, spherically averaged line-intensity power spectrum, with some works considering anisotropies while examining projection of interloper emission. We explicitly consider a simplified picture of redshift-space distortions and instrumental effects due to limited resolution, and how these distort an isotropic line-intensity signal in real space and introduce strong apparent anisotropies. The results suggest that while signal loss due to limited instrumental resolution is unavoidable, measuring the quadrupole power spectrum in addition to the monopole would still break parameter degeneracies present in monopole-only constraints, even without a measurement of the full anisotropic power spectrum.