The Tracking Tapered Gridded Estimator (TTGE) for the power spectrum from drift scan observations

TL;DR

The paper introduces the Tracking Tapered Gridded Estimator (TTGE), a new method for estimating the power spectrum from drift scan radio interferometric data, effectively reducing foreground contamination and validated through simulations.

Contribution

The paper presents the TTGE, a novel estimator that directly derives the power spectrum from drift scan visibilities, improving foreground mitigation and combining multiple tracking centers for better SNR.

Findings

TTGE recovers the input power spectrum within 20% accuracy.

Validated with simulations at 154 MHz MWA data.

Effective in reducing foreground contamination.

Abstract

Intensity mapping with the redshifted 21-cm line is an emerging tool in cosmology. Drift scan observations, where the antennas are fixed to the ground and the telescope's pointing center (PC) changes continuously on the sky due to earth's rotation, provide broad sky coverage and sustained instrumental stability needed for 21-cm intensity mapping. Here we present the Tracking Tapered Grided Estimator (TTGE) to quantify the power spectrum of the sky signal estimated directly from the visibilities measured in drift scan radio interferometric observations. The TTGE uses the data from the different PC to estimate the power spectrum of the signal from a small angular region located around a fixed tracking center (TC). The size of this angular region is decided by a suitably chosen tapering window function which serves to reduce the foreground contamination from bright sources located at large angles from the TC. It is possible to cover the angular footprint of the drift scan observations using multiple TC, and combine the estimated power spectra to increase the signal to noise ratio. Here we have validated the TTGE using simulations of $154 \, {\rm MHz}$ MWA drift scan observations. We show that the TTGE can recover the input model angular power spectrum $C_{\ell}$ within $20 \%$ accuracy over the $\ell$ range $40 < \ell < 700$.