CONFIRMATION OF WIDE-FIELD SIGNATURES IN REDSHIFTED 21 cm POWER SPECTRA

We confirm our recent prediction of the “pitchfork” foreground signature in power spectra of high-redshift 21 cm measurements where the interferometer is sensitive to large-scale structure on all baselines. This is due to the inherent response of a wide-field instrument and is characterized by enhanced power from foreground emission in Fourier modes adjacent to those considered to be the most sensitive to the cosmological H i signal. In our recent paper, many signatures from the simulation that predicted this feature were validated against Murchison Widefield Array (MWA) data, but this key pitchfork signature was close to the noise level. In this paper, we improve the data sensitivity through the coherent averaging of 12 independent snapshots with identical instrument settings and provide the first confirmation of the prediction with a signal-to-noise ratio > 10 ?> . This wide-field effect can be mitigated by careful antenna designs that suppress sensitivity near the horizon. Simple models for antenna apertures that have been proposed for future instruments such as the Hydrogen Epoch of Reionization Array and the Square Kilometre Array indicate they should suppress foreground leakage from the pitchfork by ∼40 dB relative to the MWA and significantly increase the likelihood of cosmological signal detection in these critical Fourier modes in the three-dimensional power spectrum.

[1]  A. A. Deshpande,et al.  Empirical covariance modeling for 21 cm power spectrum estimation: A method demonstration and new limits from early Murchison Widefield Array 128-tile data , 2015, 1506.01026.

[2]  S. J. Tingay,et al.  Measuring phased‐array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137 MHz ORBCOMM satellites , 2015, 1505.07114.

[3]  E. Lenc,et al.  GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey , 2015, Publications of the Astronomical Society of Australia.

[4]  Max Tegmark,et al.  FOREGROUNDS IN WIDE-FIELD REDSHIFTED 21 cm POWER SPECTRA , 2015, 1502.07596.

[5]  Roger Cappallo,et al.  The Murchison Widefield Array Commissioning Survey: A Low-Frequency Catalogue of 14 110 Compact Radio Sources over 6 100 Square Degrees , 2014, Publications of the Astronomical Society of Australia.

[6]  David R. DeBoer,et al.  WHAT NEXT-GENERATION 21 cm POWER SPECTRUM MEASUREMENTS CAN TEACH US ABOUT THE EPOCH OF REIONIZATION , 2013, 1310.7031.

[7]  Christopher L. Williams,et al.  A STUDY OF FUNDAMENTAL LIMITATIONS TO STATISTICAL DETECTION OF REDSHIFTED H i FROM THE EPOCH OF REIONIZATION , 2013, 1308.0565.

[8]  Jason Manley,et al.  OPENING THE 21 cm EPOCH OF REIONIZATION WINDOW: MEASUREMENTS OF FOREGROUND ISOLATION WITH PAPER , 2013, 1301.7099.

[9]  Alan E. E. Rogers,et al.  Science with the Murchison Widefield Array , 2012, Publications of the Astronomical Society of Australia.

[10]  A. R. Whitney,et al.  The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies , 2012, Publications of the Astronomical Society of Australia.

[11]  D. Kaplan,et al.  The EoR sensitivity of the Murchison Widefield Array , 2012, 1204.3111.

[12]  J. Prasad,et al.  Characterizing foreground for redshifted 21 cm radiation: 150 MHz Giant Metrewave Radio Telescope observations , 2012, 1208.1617.

[13]  Cathryn M. Trott,et al.  THE IMPACT OF POINT-SOURCE SUBTRACTION RESIDUALS ON 21 cm EPOCH OF REIONIZATION ESTIMATION , 2012, 1208.0646.

[14]  David F. Moore,et al.  A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE , 2012, 1204.4749.

[15]  Bryna Hazelton,et al.  FOUR FUNDAMENTAL FOREGROUND POWER SPECTRUM SHAPES FOR 21 cm COSMOLOGY OBSERVATIONS , 2012, 1202.3830.

[16]  James Aguirre,et al.  A SENSITIVITY AND ARRAY-CONFIGURATION STUDY FOR MEASURING THE POWER SPECTRUM OF 21 cm EMISSION FROM REIONIZATION , 2011, 1103.2135.

[17]  M. C. Toribio,et al.  LOFAR: The LOw-Frequency ARray , 2013, 1305.3550.

[18]  Abhirup Datta,et al.  BRIGHT SOURCE SUBTRACTION REQUIREMENTS FOR REDSHIFTED 21 cm MEASUREMENTS , 2010 .

[19]  Mervyn J. Lynch,et al.  THE PRECISION ARRAY FOR PROBING THE EPOCH OF RE-IONIZATION: EIGHT STATION RESULTS , 2009, 0904.2334.

[20]  S. Zaroubi,et al.  Foregrounds for observations of the cosmological 21 cm line - I. First Westerbork measurements of Galactic emission at 150 MHz in a low latitude field , 2009, 0904.0404.

[21]  Matias Zaldarriaga,et al.  An improved method for 21‐cm foreground removal , 2009, 0903.4890.

[22]  Christopher L. Williams,et al.  The Murchison Widefield Array: Design Overview , 2009, Proceedings of the IEEE.

[23]  Judd D. Bowman,et al.  FOREGROUND CONTAMINATION IN INTERFEROMETRIC MEASUREMENTS OF THE REDSHIFTED 21 cm POWER SPECTRUM , 2008, 0807.3956.

[24]  J. Chengalur,et al.  Foregrounds for redshifted 21-cm studies of reionization: Giant Meter Wave Radio Telescope 153-MHz observations , 2008, 0801.2424.

[25]  Andrew J. Benson,et al.  Decontamination of cosmological 21-cm maps , 2007, 0712.0497.

[26]  Max Tegmark,et al.  21 cm Tomography with Foregrounds , 2006 .

[27]  S. Furlanetto,et al.  Cosmology at low frequencies: The 21 cm transition and the high-redshift Universe , 2006, astro-ph/0608032.

[28]  J. Hewitt,et al.  Improving Foreground Subtraction in Statistical Observations of 21 cm Emission from the Epoch of Reionization , 2005, astro-ph/0510027.

[29]  Judd D. Bowman,et al.  The Sensitivity of First-Generation Epoch of Reionization Observatories and Their Potential for Differentiating Theoretical Power Spectra , 2005, astro-ph/0507357.

[30]  Matias Zaldarriaga,et al.  Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization , 2005, astro-ph/0512263.

[31]  L. Knox,et al.  Multifrequency Analysis of 21 Centimeter Fluctuations from the Era of Reionization , 2004, astro-ph/0408515.

[32]  S. Furlanetto,et al.  21 cm tomography of the high-redshift universe with the Square Kilometer Array , 2004, astro-ph/0409205.

[33]  T. D. Matteo,et al.  The 21-cm emission from the reionization epoch: extended and point source foregrounds , 2004, astro-ph/0402322.

[34]  M. Zaldarriaga,et al.  21 Centimeter Fluctuations from Cosmic Gas at High Redshifts , 2003, astro-ph/0311514.

[35]  Miguel F. Morales,et al.  Toward Epoch of Reionization Measurements with Wide-Field Radio Observations , 2003 .

[36]  P. Shapiro,et al.  On the Direct Detectability of the Cosmic Dark Ages: 21 Centimeter Emission from Minihalos , 2002, astro-ph/0202410.

[37]  IoA,et al.  Radio Foregrounds for the 21 Centimeter Tomography of the Neutral Intergalactic Medium at High Redshifts , 2001, astro-ph/0109241.

[38]  M. Rees,et al.  Radio Signatures of H I at High Redshift: Mapping the End of the “Dark Ages” , 1999, astro-ph/9903139.

[39]  M. Rees,et al.  21 Centimeter Tomography of the Intergalactic Medium at High Redshift , 1996, astro-ph/9608010.

[40]  Martin J. Rees,et al.  The 21-cm line at high redshift: a diagnostic for the origin of large scale structure , 1990 .

[41]  F. Zernike.  The concept of degree of coherence and its application to optical problems , 1938 .

[42]  P. H. Cittert,et al.  Die Wahrscheinliche Schwingungsverteilung in Einer von Einer Lichtquelle Direkt Oder Mittels Einer Linse Beleuchteten Ebene , 1934 .