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

被引：256

作者：

Mertens, F. G. ^{[1
,2
]}

Mevius, M. ^{[3
]}

Koopmans, L. V. E. ^{[1
]}

Offringa, A. R. ^{[3
]}

Mellema, G. ^{[4
]}

Zaroubi, S. ^{[1
,5
,6
]}

Brentjens, M. A. ^{[3
]}

Gan, H. ^{[1
]}

Gehlot, B. K. ^{[7
]}

Pandey, V. N. ^{[3
]}

Sardarabadi, A. M. ^{[1
]}

Vedantham, H. K. ^{[3
]}

Yatawatta, S. ^{[3
]}

Asad, K. M. B. ^{[8
]}

Ciardi, B. ^{[9
]}

Chapman, E. ^{[10
]}

Gazagnes, S. ^{[1
]}

Ghara, R. ^{[4
,5
,6
]}

Ghosh, A. ^{[11
,12
,13
]}

Giri, S. K. ^{[4
]}

Iliev, I. T. ^{[14
]}

Jelic, V ^{[15
]}

Kooistra, R. ^{[16
]}

Mondal, R. ^{[14
]}

Schaye, J. ^{[17
]}

Silva, M. B. ^{[18
]}

机构：

[1] Univ Groningen, Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands

[2] PSL Res Univ, Sorbonne Univ, Observ Paris, CNRS,LERMA, F-75014 Paris, France

[3] Astron, POB 2, NL-7990 AA Dwingeloo, Netherlands

[4] Stockholm Univ, Oskar Klein Ctr, Dept Astron, AlbaNova, SE-10691 Stockholm, Sweden

[5] Open Univ Israel, Dept Nat Sci, 1 Univ Rd,POB 808, IL-4353701 Raanana, Israel

[6] Technion, Dept Phys, IL-32000 Haifa, Israel

[7] Arizona State Univ, Sch Earth & Space Explorat, 781 Terrace Mall, Tempe, AZ 85287 USA

[8] Independent Univ Bangladesh, Plot 16,Block B,Aftabuddin Ahmed Rd, Dhaka 1229, Bangladesh

[9] Max Planck Inst Astrophys, Karl Schwarzschild Str 1, D-85748 Garching, Germany

[10] Imperial Coll London, Blacken Lab, Astrophys Grp, Prince Coruna Rd, London SW7 2AZ, England

[11] Univ Western Cape, Dept Phys, ZA-7535 Cape Town, South Africa

[12] SARAO, 2 Fir St,Black River Pk, ZA-7925 Cape Town, South Africa

[13] Banwarilal Bhalotia Coll, Dept Phys, Asansol 713303, W Bengal, India

[14] Univ Sussex, Astron Ctr, Dept Phys & Astron, Pevensey 2 Bldg, Brighton BN1 9QH, E Sussex, England

[15] Rudjer Boskovic Inst, Bijenicka Cesta 54, Zagreb 10000, Croatia

[16] Univ Tokyo, UTIAS, Kavli IPMU WPI, Kashiwa, Chiba 2778583, Japan

[17] Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands

[18] Univ Oslo, Inst Theoret Astrophys, POB 1029 Blindern, N-0315 Oslo, Norway

来源：

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | 2020年 / 493卷 / 02期

基金：

英国科学技术设施理事会; 瑞典研究理事会;

关键词：

methods: data analysis; techniques: interferometric; dark ages; reionization; first stars; cosmology: observations; POLARIZATION LEAKAGE; HIGH-REDSHIFT; REIONIZATION WINDOWS; 21-CM SIGNAL; COSMIC DAWN; SKY SURVEY; EPOCH; CALIBRATION; SIMULATIONS; IMPACT;

D O I：

10.1093/mnras/staa327

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

A new upper limit on the 21 cm signal power spectrum at a redshift of z approximate to 9.1 is presented, based on 141 h 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-sigma upper limit of Delta(2)(21) < (73)(2) mK(2) at k = 0.075 h cMpc(-1) is found, an improvement by a factor approximate to 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 radiofrequency interference. We discuss future improvements to the signal processing chain that can further reduce or even eliminate these causes of excess power.

引用

页码：1662 / 1685

页数：24

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