ALL-SKY INTERFEROMETRY WITH SPHERICAL HARMONIC TRANSIT TELESCOPES

By J. Shaw, K. Sigurdson, Ue-Li Pen, A. Stebbins, M. Sitwell. 2013

144 citations recorded by the source corpus.

In this paper, we describe the spherical harmonic transit telescope through the use of a novel formalism for the analysis of transit radio telescopes. This all-sky approach bypasses the curved-sky complications of traditional interferometry and so is particularly well-suited to the analysis of wide-field radio interferometers. It enables compact and computationally efficient representations of the data and its statistics, which allow new ways of approaching important problems like map-making and foreground removal. In particular, we show how it enables the use of the Karhunen-Loève transform as a highly effective foreground filter, suppressing realistic foreground residuals for our fiducial example by at least a factor 20 below the 21 cm signal, even in highly contaminated regions of the sky. This is despite the presence of the mode-mixing inherent in real-world instruments with frequency-dependent beams. We show, using Fisher forecasting, that foreground cleaning has little effect on power spectrum constraints compared to hypothetical foreground-free measurements. Beyond providing a natural real-world data analysis framework for 21 cm telescopes now under construction and future experiments, this formalism allows accurate power spectrum forecasts to be made that include the interplay of design constraints and realistic experimental systematics with 21st century 21 cm science.

Subfields: Aerospace Engineering, Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9cbe315f476caa96761d5a3e35a0626264366b8d

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Citations in the corpus

An improved source-subtracted and destriped 408 MHz all-sky map (2014, methodology): “…template of synchrotron emission would be particularly useful for preparing for upcoming 21 cm experiments, e.g. SKA and HI intensity mapping experiments, in particular to allow the study of foreground cleaning techniques for such projects (see e.g. Wolz et al. 2014; Shaw et al. 2014).”
New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7 (2013, background): “Such filters would essentially correspond to a one-dimensional implementation of the inverse primary beam uv-gridding discussed in Morales & Matejek (2009), and have many features in common with m-mode synthesis described in Shaw et al. (2014).”
Canadian Hydrogen Intensity Mapping Experiment (CHIME) pathfinder (2014, methodology): “Using the m-mode formalism, the two-dimensional matter power spectrum can be reconstructed in the presence of foregrounds.(15,16) As expected we lose sensitivity to the largest scale fluctuations in the line-of-sight direction, but still retain significant sensitivity to the peaks of the BAO.”