Browsing by Author "Townsend, Junaid"

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    H I intensity mapping with the MIGHTEE Survey: first results of the H I power spectrum
    (Oxford University Press, 2025) Taylor, Russ; Santos, Mario G.; Townsend, Junaid; Taylor, Russ
    We present the first results of the H I intensity mapping power spectrum analysis with the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) survey. We use data covering ∼ 4 square degrees in the COSMOS field using a frequency range of 962.5–1008.42 MHz, equivalent to H I emission in 0.4 < z < 0.48. The data consist of 15 pointings with a total of 94.2 h on-source. We verify the suitability of the MIGHTEE data for H I intensity mapping by testing for residual systematics across frequency, baselines, and pointings. We also vary the window used for H I signal measurements and find no significant improvement using stringent Fourier mode cuts. We compute the H I power spectrum at scales 0.5 Mpc−1 ≾ k ≾ 10 Mpc−1 in autocorrelation as well as cross-correlation between observational scans using power spectrum domain averaging for pointings. We report consistent upper limits of 29.8 mK2 Mpc3 from the 2σ cross-correlation measurements and 25.82 mK2 Mpc3 from autocorrelation at k ∼2 Mpc−1.The low signal-to-noise ratio in this data potentially limits our ability to identify residual systematics, which will be addressed in the future by incorporating more data in the analysis.
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    HI intensity mapping with the MIGHTEE survey: power spectrum estimates
    (Monthly Notices of the Royal Astronomical Society, 2021) Sourabh, Paul; Santos, Mario; Townsend, Junaid
    Intensity mapping (IM) with neutral hydrogen is a promising avenue to probe the large scale structure of the Universe. In this paper, we demonstrate that using the 64-dish MeerKAT radio telescope as a connected interferometer, it is possible to make a statistical detection of HI in the post-reionization Universe. With the MIGHTEE (MeerKAT International GHz Tiered Extragalactic Exploration) survey project ob- serving in the L-band (856 < < 1712 MHz, z < 0:66), we can achieve the required sensitivity to measure the HI IM power spectrum on quasi-linear scales, which will provide an important complementarity to the single-dish IM MeerKAT observations. We present a purpose-built simulation pipeline that emulates the MIGHTEE obser- vations and forecast the constraints that can be achieved on the HI power spectrum at z = 0:27 for k > 0:3 Mpc􀀀1 using the foreground avoidance method. We present the power spectrum estimates with the current simulation on the COSMOS eld that includes contributions from HI, noise and point source models constructed from the observed MIGHTEE data. The results from our visibility based pipeline are in qualitative 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 quasi-linear scales (signal-to-noise ratio > 7 at k = 0:49 Mpc􀀀1) which are instrumental in probing cosmological quantities such as the spectral index of uctuation, constraints on warm dark matter, the quasi-linear redshift space distortions and the measurement of the HI content of the Universe up to z 0:5.