Details

Autor(en) / Beteiligte

• Gehlot, B K
• Mertens, F G
• Koopmans, L V E
• Offringa, A R
• Shulevski, A
• Mevius, M
• Brentjens, M A
• Kuiack, M
• Pandey, V N
• Rowlinson, A
• Sardarabadi, A M
• Vedantham, H K
• Wijers, R A M J
• Yatawatta, S
• Zaroubi, S

Titel

The AARTFAAC Cosmic Explorer: observations of the 21-cm power spectrum in the EDGES absorption trough

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2020-12, Vol.499 (3), p.4158-4173

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2020

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• ABSTRACT The 21-cm absorption feature reported by the EDGES collaboration is several times stronger than that predicted by traditional astrophysical models. If genuine, a deeper absorption may lead to stronger fluctuations on the 21-cm signal on degree scales (up to 1 K in rms), allowing these fluctuations to be detectable in nearly 50 times shorter integration times compared to previous predictions. We commenced the ‘AARTFAAC Cosmic Explorer’ (ACE) program, which employs the AARTFAAC wide-field image, to measure or set limits on the power spectrum of the 21-cm fluctuations in the redshift range z = 17.9–18.6 (Δν = 72.36–75.09 MHz) corresponding to the deep part of the EDGES absorption feature. Here, we present first results from two LST bins: 23.5–23.75 and 23.75–24.00 h, each with 2 h of data, recorded in ‘semi drift-scan’ mode. We demonstrate the application of the new ACE data-processing pipeline (adapted from the LOFAR-EoR pipeline) on the AARTFAAC data. We observe that noise estimates from the channel and time-differenced Stokes V visibilities agree with each other. After 2 h of integration and subtraction of bright foregrounds, we obtain 2σ upper limits on the 21-cm power spectrum of $\Delta _{21}^2 \lt (8139~\textrm {mK})^2$ and $\Delta _{21}^2 \lt (8549~\textrm {mK})^2$ at $k = 0.144~h\, \textrm {cMpc}^{-1}$ for the two LST bins. Incoherently averaging the noise bias-corrected power spectra for the two LST bins yields an upper limit of $\Delta _{21}^2 \lt (7388~\textrm {mK})^2$ at $k = 0.144~h\, \textrm {cMpc}^{-1}$. These are the deepest upper limits thus far at these redshifts.