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

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.