Towards Optimal Foreground Mitigation Strategies for Interferometric HI Intensity Mapping in the Low-Redshift Universe. (arXiv:2205.07776v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Z/0/1/0/all/0/1">Zhaoting Chen</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Wolz_L/0/1/0/all/0/1">Laura Wolz</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Battye_R/0/1/0/all/0/1">Richard Battye</a> (1) ((1) Jodrell Bank Centre for Astrophysics)
We conduct the first case study towards developing optimal foreground
mitigation strategies for neutral hydrogen (HI) intensity mapping using radio
interferometers at low redshifts. A pipeline for simulation, foreground
mitigation and power spectrum estimation is built, which can be used for
ongoing and future surveys using MeerKAT and SKAO. It simulates realistic sky
signals to generate visibility data given instrument and observation
specifications, which is subsequently used to perform foreground mitigation and
power spectrum estimation. A quadratic estimator formalism is developed to
estimate the temperature power spectrum in visibility space. Using MeerKAT
telescope specifications for observations in the redshift range z~0.25-0.30
corresponding to the MIGHTEE survey, we present a case study where we compare
different approaches of foreground mitigation. We find that component
separation in visibility space provides a more accurate estimation of HI
clustering comparing to foreground avoidance, with the uncertainties being 30%
smaller. Power spectrum estimation from image is found to be less robust with
larger bias and more information loss when compared to estimation in
visibility. We conclude that for z~0.25-0.30, the MIGHTEE survey will be
capable of measuring the HI power spectrum from k~0.5 Mpc$^{-1}$ to k~10
Mpc$^{-1}$ with high accuracy. We are the first to show that, at low redshift,
component separation in visibility space suppresses foreground contamination at
large line-of-sight scales, allowing measurement of HI power spectrum closer to
the foreground wedge, crucial for data analysis towards future detections.
We conduct the first case study towards developing optimal foreground
mitigation strategies for neutral hydrogen (HI) intensity mapping using radio
interferometers at low redshifts. A pipeline for simulation, foreground
mitigation and power spectrum estimation is built, which can be used for
ongoing and future surveys using MeerKAT and SKAO. It simulates realistic sky
signals to generate visibility data given instrument and observation
specifications, which is subsequently used to perform foreground mitigation and
power spectrum estimation. A quadratic estimator formalism is developed to
estimate the temperature power spectrum in visibility space. Using MeerKAT
telescope specifications for observations in the redshift range z~0.25-0.30
corresponding to the MIGHTEE survey, we present a case study where we compare
different approaches of foreground mitigation. We find that component
separation in visibility space provides a more accurate estimation of HI
clustering comparing to foreground avoidance, with the uncertainties being 30%
smaller. Power spectrum estimation from image is found to be less robust with
larger bias and more information loss when compared to estimation in
visibility. We conclude that for z~0.25-0.30, the MIGHTEE survey will be
capable of measuring the HI power spectrum from k~0.5 Mpc$^{-1}$ to k~10
Mpc$^{-1}$ with high accuracy. We are the first to show that, at low redshift,
component separation in visibility space suppresses foreground contamination at
large line-of-sight scales, allowing measurement of HI power spectrum closer to
the foreground wedge, crucial for data analysis towards future detections.
http://arxiv.org/icons/sfx.gif
