The Tracking Tapered Gridded Estimator for the 21-cm power spectrum from MWA drift scan observations I: Validation and preliminary results

Abstract

Drift scan observations provide the broad sky coverage and instrumental stability needed to measure the Epoch of Reionization (EoR) 21-cm signal. In such observations, the telescope's pointing center (PC) moves continuously on the sky. The Tracking Tapered Gridded Estimator (TTGE) combines observations from different PC to estimate $P(k_{\perp },k_{\parallel })$ the 21-cm power spectrum, centered on a tracking center (TC) which remains fixed on the sky. The tapering further restricts the sky response to a small angular region around TC, thereby mitigating wide-field foregrounds. Here we consider $154.2\mathrm{MHz}$ ($z=8.2$) Murchison Widefield Array (MWA) drift scan observations. The periodic pattern of flagged channels, present in MWA data, is known to introduce artefacts which pose a challenge for estimating $P(k_{\perp },k_{\parallel })$. We demonstrate that the TTGE is able to recover $P(k_{\perp },k_{\parallel })$ without any artefacts, and estimate $P(k)$ within $5\%$ accuracy over a large $k$-range. We also present preliminary results for a single PC, combining 9 nights of observation $(17\min$ total). We find that $P(k_{\perp },k_{\parallel })$ exhibits streaks at a fixed interval of $k_{\parallel }=0.29{\mathrm{Mpc}}^{-1}$, which matches $\Delta {\nu }_{\mathrm{per}}=1.28\mathrm{MHz}$ that is the period of the flagged channels. The streaks are not as pronounced at larger $k_{\parallel }$, and in some cases they do not appear to extend across the entire $k_{\perp }$ range. The rectangular region $0.05\le k_{\perp }\le 0.16\mathrm{Mp}{\mathrm{c}}^{-1}$ and $0.9\le k_{\parallel }\le 4.6\mathrm{Mp}{\mathrm{c}}^{-1}$ is found to be relatively free of foreground contamination and artefacts, and we have used this to place the $2\sigma$ upper limit ${\Delta }^2(k)<(1.85\times 10^4{)}^2\mathrm{m}{\mathrm{K}}^2$ on the EoR 21-cm mean squared brightness temperature fluctuations at $k=1{\mathrm{Mpc}}^{-1}$.

15 pages, 11 figures, accepted for publication in PASA

References in corpus (19)

• On using visibility correlations to probe the HI distribution from the dark ages to the present epoch I: Formalism and the expected signal
• Spectral Index of the Diffuse Radio Background Measured From 100 to 200 MHz
• Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations
• Characterizing Foreground for redshifted 21-cm radiation: 150 MHz GMRT observations
• The multi-frequency angular power spectrum of the epoch of reionization 21 cm signal
• Visibility based angular power spectrum estimation in low frequency radio interferometric observations
• Towards simulating and quantifying the light-cone EoR 21-cm signal
• GMRT observation towards detecting the Post-reionization 21-cm signal
• New EoR Power Spectrum Limits From MWA Phase II Using the Delay Spectrum Method and Novel Systematic Rejection
• The angular power spectrum measurement of the Galactic synchrotron emission in two fields of the TGSS survey
• A Tapered Gridded Estimator (TGE) for the Multi-Frequency Angular Power Spectrum (MAPS) and the Cosmological HI 21-cm Power Spectrum
• Statistical recovery of 21cm visibilities and their power spectra with Gaussian constrained realisations and Gibbs sampling
• Extracting the 21 cm EoR signal using MWA drift scan data
• Towards 21-cm Intensity Mapping at $z=2.28$ with uGMRT using the Tapered Gridded Estimator I: Foreground Avoidance
• Towards $21$-cm intensity mapping at $z=2.28$ with uGMRT using the tapered gridded estimator III: Foreground removal
• Line Expansion Opacity in Relativistically Expanding Media
• Towards $21$-cm intensity mapping at $z=2.28$ with uGMRT using the tapered gridded estimator -- IV. Wideband analysis
• The auto and cross angular power spectrum of the Cas A supernova remnant in radio and X-ray
• The Tracking Tapered Gridded Estimator (TTGE) for the power spectrum from drift scan observations

Cited by in corpus (3)

• Prospects for Observing High-redshift Radio-loud Quasars in the SKA Era: Paving the Way for 21-cm Forest Observations
• The Evolving Power Spectrum for the light cone Epoch of Reionization (EoR) 21-cm signal
• Bayes-SCF: A Bayesian filter to mitigate foreground leakage in the 21-cm power spectrum