Upper limits on the 21 cm Epoch of Reionization power spectrum from one night with LOFAR

Patil, A H, Iliev, I T and et al, (2017) Upper limits on the 21 cm Epoch of Reionization power spectrum from one night with LOFAR. Astrophysical Journal, 838 (1). a65. ISSN 0004-637X

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Abstract

We present the first limits on the Epoch of Reionization 21 cm H I power spectra, in the redshift range z = 7.9–10.6, using the Low-Frequency Array (LOFAR) High-Band Antenna (HBA). In total, 13.0 hr of data were used from observations centered on the North Celestial Pole. After subtraction of the sky model and the noise bias, we detect a non-zero I 56 13 mK D2 =  2 ( ) (1-σ) excess variance and a best 2-σ upper limit of 21 79.6 mK D2 < 2 ( ) at k = 0.053 h cMpc−1 in the range z = 9.6–10.6. The excess variance decreases when optimizing the smoothness of the direction- and frequency dependent gain calibration, and with increasing the completeness of the sky model. It is likely caused by (i) residual side-lobe noise on calibration baselines, (ii) leverage due to nonlinear effects, (iii) noise and ionosphere-induced gain errors, or a combination thereof. Further analyses of the excess variance will be discussed in forthcoming publications.

Item Type: Article
Keywords: dark ages, reionization, first stars
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Astronomy Centre
Subjects: Q Science > QB Astronomy > QB0460 Astrophysics
Q Science > QB Astronomy > QB0468 Non-optical methods of astronomy
Depositing User: Ilian Iliev
Date Deposited: 22 Jun 2017 07:53
Last Modified: 22 Jun 2017 07:56
URI: http://sro.sussex.ac.uk/id/eprint/68780

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