# Impact of $1/f$ noise on cosmological parameter constraints for SKA intensity mapping

## TL;DR

This study assesses how $1/f$ noise affects cosmological parameter constraints in SKA intensity mapping, showing that noise degrades precision but can be mitigated with optimized scan strategies.

## Contribution

It provides a quantitative forecast of $1/f$ noise impact on SKA cosmology constraints using a Fisher matrix approach and explores mitigation strategies.

## Key findings

- $1/f$ noise degrades parameter constraints by ~20-50%.
- Higher redshift and smaller scales are more affected by $1/f$ noise.
- Optimal scan strategies can reduce the impact of $1/f$ noise.

## Abstract

We investigate the impact of $1/f$ noise on cosmology for an intensity mapping survey with SKA1-MID Band\,1 and Band\,2. We use a Fisher matrix approach to forecast constraints on cosmological parameters under the influence of $1/f$ noise, adopting a semi-empirical model from an earlier work, which results from the residual $1/f$ noise spectrum after applying a component separation algorithm to remove smooth spectral components. Without $1/f$ noise, the projected constraints are $4\%$ on $w_0$, $1\%$ on $h$, $2\%$ on $b_{\rm HI}$ using Band\,1+\emph{Planck}, and $3\%$ on $w_0$, $0.5\%$ on $h$, $2\%$ on $b_{\rm HI}$ using Band\,2+\emph{Planck}. A representative baseline $1/f$ noise degrades these constraints by a factor of $\sim1.5$ for Band\,1+\emph{Planck}, and $\sim1.2$ for Band\,2+\emph{Planck}. On the power spectrum measurement, higher redshift and smaller scales are more affected by $1/f$ noise, with minimal contamination comes from $z\lesssim1$ and $\ell\lesssim100$. Subject to the specific scan strategy of the adopted $1/f$ noise model, one prefers a correlated in frequency with minimised spectral slope, a low knee frequency, and a large telescope slew speed in order to reduce its impact.