HI intensity mapping with the MIGHTEE survey: power spectrum estimates

Intensity mapping (IM) with neutral hydrogen is a promising avenue to probe the large scale structure of the Universe. With MeerKAT single-dish measurements, we are constrained to scales $>1$ degree, and this will allow us to set important constraints on the Baryon acoustic oscillations and redshift space distortions. However, with MeerKAT's interferometric observation, we can also probe relevant cosmological scales. In this paper, we establish that we can make a statistical detection of HI with one of MeerKAT's existing large survey projects (MIGHTEE) on semi-linear scales, which will provide a useful complementarity to the single-dish IM. We present a purpose-built simulation pipeline that emulates the MIGHTEE observations and forecast the constraints that can be achieved on the HI power spectrum at $z = 0.27$ for $k > 0.3$ $\rm{Mpc}^{-1}$ using the foreground avoidance method. We present the power spectrum estimates with the current simulation on the COSMOS field that includes contributions from HI, noise and point source models from the data itself. The results from our \textit{visibility} based pipeline are in good agreement to the already available MIGHTEE data. This paper demonstrates that MeerKAT can achieve very high sensitivity to detect HI with the full MIGHTEE survey on semi-linear scales (signal-to-noise ratio $> 7$ at $k=0.49$ $\rm{Mpc}^{-1}$) which are instrumental in probing cosmological quantities such as the spectral index of fluctuation, constraints on warm dark matter, the quasi-linear redshift space distortions and the measurement of the HI content of the Universe up to $z\sim 0.5$.