Neutral hydrogen intensity mapping on small scales using MeerKAT

>Magister Scientiae - MScIn the post-reionisation universe, intensity mapping (IM) with the 21 cm line of neutral hydrogen (HI) provides a potential means of probing the large-scale structure of the universe. With such a probe, a wide variety of interesting phenomena such as the Baryon Acoustic Oscillations (BAO) and Redshift Space Distortions (RSD) can be studied. The MeerKAT telescope has the potential to make full use of this technique, especially in the single-dish mode, which will probe the scales relevant to BAO and RSD. A useful complementary of this is HI IM with MeerKAT in interferometer-mode, which will enable the extraction of cosmological information on semi-linear and small scales. In this study, full end-to-end simulations of interferometric observations with MeerKAT for HI IM were developed. With this, the power spectrum extraction was analysed using the foreground avoidance technique. This took into account the foreground wedge from point source contamination extracted from real MIGHTEE COSMOS data, as well as RFI flagging. The errors on the power spectrum estimator were then calculated through a Monte Carlo process using 1000s of realisations of both the thermal noise and HI signal. In doing so, precision constraints on the HI power spectrum are found at z = 0:27 on scales 0:4 < k < 10 Mpc-1 for mock visibility data sets which contain the HI signal contaminated by noise, mimicking the MIGHTEE COSMOS field for total observation times & 20 hours. These results illustrate the potential of doing precision cosmology with MeerKAT’s MIGHTEE survey and interferometer-mode HI IM

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 $z\sim 0.5$.Comment: 12 pages, 8 figures, Submitted to MNRAS, comments welcom

H I 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. 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 H I in the post-reionization Universe. With the MIGHTEE (MeerKAT International GHz Tiered Extragalactic Exploration) survey project observing in the L-band (856 MHz 0.3 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 H I, 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 H I with the full MIGHTEE survey on quasi-linear scales (signal-to-noise ratio >7 at k = 0.49 Mpc−1⁠) that 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 H I content of the Universe up to z ∼ 0.5

Hydrogen Intensity and Real-Time Analysis Experiment: 256-element array status and overview

International audienceThe Hydrogen Intensity and Real-time Analysis Experiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element array to be deployed at the South African Radio Astronomy Observatory Square Kilometer Array site in South Africa. Each of the 6 m, f  /  0.23 dishes will be instrumented with dual-polarization feeds operating over a frequency range of 400 to 800 MHz. Through intensity mapping of the 21 cm emission line of neutral hydrogen, HIRAX will provide a cosmological survey of the distribution of large-scale structure over the redshift range of 0.775  <  z  <  2.55 over ∼15,000 square degrees of the southern sky. The statistical power of such a survey is sufficient to produce ∼7  %   constraints on the dark energy equation of state parameter when combined with measurements from the Planck satellite. Additionally, HIRAX will provide a highly competitive platform for radio transient and HI absorber science while enabling a multitude of cross-correlation studies. We describe the science goals of the experiment, overview of the design and status of the subcomponents of the telescope system, and describe the expected performance of the initial 256-element array as well as the planned future expansion to the final, 1024-element array