Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR

Patil, A. H.; Yatawatta, S.; Koopmans, L. V. E.; de Bruyn, A. G.; Brentjens, M. A.; Zaroubi, S.; Asad, K. M. B.; Hatef, M.; Jelić, Vibor; Mevius, M.; Offringa, A. R.; Pandey, V. N.; Vedantham, H.; Abdalla, F. B.; Brouw, W. N.; Chapman, E.; Ciardi, B.; Gehlot, B. K.; Ghosh, A.; Harker, G.; Iliev, I. T.; Kakiichi, K.; Majumdar, S.; Mellema, G.; Silva, M. B.; Schaye, J.; Vrbanec, D.; Wijnholds, S. J. (2017) Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR. Astrophysical Journal, 838 (1). pp. 65-81. 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 {;{;{;Δ };};};{;{;I};};2={;(56+/- 13{;mK};)};2 (1-σ) excess variance and a best 2-σ upper limit of {;{;{;Δ };};};212< {;(79.6{;mK};)};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
Uncontrolled Keywords:	dark ages; reionization; first stars
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Divisions:	Division of Experimental Physics
Depositing User:	Vibor Jelić
Date Deposited:	24 Apr 2017 13:04
URI:	http://fulir.irb.hr/id/eprint/3461
DOI:	10.3847/1538-4357/aa63e7

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