A new MWA limit on the 21 cm power spectrum at redshifts ∼13–17. Issue 4 (1st June 2021)

• Record Type: Journal Article
• Authors: Yoshiura, S; Pindor, B; Line, J L B; Barry, N; Trott, C M; Beardsley, A; Bowman, J; Byrne, R; Chokshi, A; Hazelton, B J; Hasegawa, K; Howard, E; Greig, B; Jacobs, D; Jordan, C H; Joseph, R; Kolopanis, M; Lynch, C; McKinley, B; Mitchell, D A; Morales, M F; Murray, S G; Pober, J C; Rahimi, M; Takahashi, K; Tingay, S J; Wayth, R B; Webster, R L; Wilensky, M; Wyithe, J S B; Zhang, Z; Zheng, Q;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 505:Issue 4(2021)
• Page Start: 4775
• Page End: 4790
• Publication Date: 2021-06-01
• Subjects: methods: data analysis -- dark ages, reionization, first stars; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1560
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Observations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz have the potential to constrain the distribution of neutral hydrogen in the intergalactic medium at redshift ∼13–17. Using 15 h of MWA data, we analyse systematics in this band such as radio-frequency interference (RFI), ionospheric and wide field effects. By updating the position of point sources, we mitigate the direction-independent calibration error due to ionospheric offsets. Our calibration strategy is optimized for the lowest frequency bands by reducing the number of direction-dependent calibrators and taking into account radio sources within a wider field of view. We remove data polluted by systematics based on the RFI occupancy and ionospheric conditions, finally selecting 5.5 h of the cleanest data. Using these data, we obtain 2σ upper limits on the 21 cm power spectrum in the range of $0.1~ h~{\mathrm{ Mpc}}^{-1}\lessapprox k \lessapprox 1 ~ ~h~{\mathrm{ Mpc}}^{-1}$ and at z = 14.2, 15.2, and 16.5, with the lowest limit being $6.3\times 10^6 ~\rm mK^2$ at $k=0.14 ~h~{\mathrm{ Mpc}}^{-1}$ and at z = 15.2 with a possibility of a few per cent of signal loss due to direction-independent calibration.