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.; Bruyn, A. G. de; Brentjens, M. A.; Zaroubi, Saleem; Asad, K. M. B.; Hatef, M.; Jelić, Vibor; Mevius, M.; Offringa, A. R.; Pandey, V. N.; Vedantham, H. K.; Abdalla, F. B.; Brouw, W. N.; Chapman, Emma; Ciardi, B.; Gehlot, B. K.; Ghosh, A.; Harker, G.; Iliev, Ilian T.; Kakiichi, Koki; Majumdar, Suman; Mellema, Garrelt; Silva, M.B.; Schaye, Joop; Vrbanec, Damir; Wijnholds, Stefan J.

doi:10.3847/1538-4357/aa63e7

Cited by 284 publications

(381 citation statements)

References 90 publications

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“…The LOFAR EoR KSP targets mainly two deep fields: the NCP and the field surrounding the bright compact radio source 3C 196 (de Bruyn & LOFAR EoR Key Science Project Team 2012). Here we present results on the NCP field for which we already published an upper limit on the 21cm signal based on 13 hours of data (Patil et al 2017). The NCP can be observed every night of the year, making it an excellent EoR window.…”

Section: Lofar-hba Observationsmentioning

confidence: 99%

“…The intensity scale of our sky model is set by NVSS J011732+892848 (RA 01h 17m 33s, Dec 89°28' 49" in J2000) (see Fig. 2), a flat spectrum source with an intrinsic 12 Shapelets form an orthonormal basis in which a source of arbitrary shape can be described by a limited number of coefficients with sufficient accuracy (Yatawatta 2011). flux of 8.1 Jy with 5% accuracy (Patil et al 2017). The flux and spectrum of this source were obtained following a calibration against 3C295 in the range 120 − 160 MHz (Patil et al 2017).…”

Section: The Ncp Sky Modelmentioning

confidence: 99%

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Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

Mertens

Mevius

Koopmans

et al. 2020

Monthly Notices of the Royal Astronomical Society

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278

263

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A new upper limit on the 21-cm signal power spectrum at a redshift of z ≈ 9.1 is presented, based on 141 hours of data obtained with the Low-Frequency Array (LOFAR). The analysis includes significant improvements in spectrally-smooth gain-calibration, Gaussian Process Regression (GPR) foreground mitigation and optimally-weighted power spectrum inference. Previously seen 'excess power' due to spectral structure in the gain solutions has markedly reduced but some excess power still remains with a spectral correlation distinct from thermal noise. This excess has a spectral coherence scale of 0.25 − 0.45 MHz and is partially correlated between nights, especially in the foreground wedge region. The correlation is stronger between nights covering similar local sidereal times. A best 2-σ upper limit of ∆ 2 21 < (73) 2 mK 2 at k = 0.075 h cMpc −1 is found, an improvement by a factor ≈ 8 in power compared to the previously reported upper limit. The remaining excess power could be due to residual foreground emission from sources or diffuse emission far away from the phase centre, polarization leakage, chromatic calibration errors, ionosphere, or low-level radio-frequency interference. We discuss future improvements to the signal processing chain that can further reduce or even eliminate these causes of excess power.

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Section: Lofar-hba Observationsmentioning

confidence: 99%

Section: The Ncp Sky Modelmentioning

confidence: 99%

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

Mertens

Mevius

Koopmans

et al. 2020

Monthly Notices of the Royal Astronomical Society

Self Cite

278

263

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“…In theory, the solution to this problem would be to measure the beams then iterate through a "self-calibration to sky model" loop that includes direction dependent gains for all antennas (Bhatnagar et al, 2008;Smirnov & Tasse, 2015). In practice, such a process remains at the limit of computational abilities (Patil et al, 2017).…”

Section: Radio Sciencementioning

confidence: 99%

H I 21‐cm Cosmology and the Bispectrum: Closure Diagnostics in Massively Redundant Interferometric Arrays

Carilli¹,

Nikolic²,

Thyagarajan³

et al. 2018

Radio Science

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New, massively redundant low‐frequency arrays allow for a novel investigation of closure relations in interferometry. We employ commissioning data from the Hydrogen Epoch of Reionization Array to investigate closure quantities in this densely packed grid array of 14‐m antennas operating at 100 to 200 MHz. We investigate techniques that utilize closure phase spectra for redundant triads to estimate departures from redundancy for redundant baseline visibilities. We find a median absolute deviation from redundancy in closure phase across the observed frequency range of about 4.5°. This value translates into a nonredundancy per visibility phase of about 2.6°, using prototype electronics. The median absolute deviations from redundancy decrease with longer baselines. We show that closure phase spectra can be used to identify ill‐behaved antennas in the array, independent of calibration. We investigate the temporal behavior of closure spectra. The Allan variance increases after a 1‐min stride time, due to passage of the sky through the primary beam of the transit telescope. However, the closure spectra repeat to well within the noise per measurement at corresponding local sidereal times from day to day. In future papers in this series we will develop the technique of using closure phase spectra in the search for the H I 21‐cm signal from cosmic reionization.

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“…Note that the PAPER collaboration initially reported a strong upper bound (Beardsley et al 2016) which was later revised to a weaker upper bound (Cheng et al 2018;Kolopanis et al 2019). The first LOFAR upper limit on the power spectrum of the signal obtained from one night observation was (79.6) 2 mK 2 at k = 0.053 h Mpc −1 and a redshift between 9.6 and 10.6 (Patil et al 2017). Recently, upper limits were provided for even higher redshifts.…”

Section: Introductionmentioning

confidence: 99%

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

Ghara

Giri

Mellema

et al. 2020

Monthly Notices of the Royal Astronomical Society

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106

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We derive constraints on the thermal and ionization states of the intergalactic medium (IGM) at redshift ≈ 9.1 using new upper limits on the 21-cm power spectrum measured by the LO-FAR radio-telescope and a prior on the ionized fraction at that redshift estimated from recent cosmic microwave background (CMB) observations. We have used results from the reionization simulation code GRIZZLY and a Bayesian inference framework to constrain the parameters which describe the physical state of the IGM. We find that, if the gas heating remains negligible, an IGM with ionized fraction 0.13 and a distribution of the ionized regions with a characteristic size 8 h −1 comoving megaparsec (Mpc) and a full width at the half maximum (FWHM) 16 h −1 Mpc is ruled out. For an IGM with a uniform spin temperature T S 3 K, no constraints on the ionized component can be computed. If the large-scale fluctuations of the signal are driven by spin temperature fluctuations, an IGM with a volume fraction 0.34 of heated regions with a temperature larger than CMB, average gas temperature 7-160 K and a distribution of the heated regions with characteristic size 3.5-70 h −1 Mpc and FWHM of 110 h −1 Mpc is ruled out. These constraints are within the 95 per cent credible intervals. With more stringent future upper limits from LOFAR at multiple redshifts, the constraints will become tighter and will exclude an increasingly large region of the parameter space.

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

Cited by 284 publications

References 90 publications

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

H I 21‐cm Cosmology and the Bispectrum: Closure Diagnostics in Massively Redundant Interferometric Arrays

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

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