Empirical Covariance Modeling for 21 cm Power Spectrum Estimation: A Method Demonstration and New Limits from Early Murchison Widefield Array 128-Tile Data
Abstract
The separation of the faint cosmological background signal from bright astrophysical foregrounds remains one of the most daunting challenges of mapping the high-redshift intergalactic medium with the redshifted 21 cm line of neutral hydrogen. Advances in mapping and modeling of diffuse and point source foregrounds have improved subtraction accuracy, but no subtraction scheme is perfect. Precisely quantifying the errors and error correlations due to missubtracted foregrounds allows for both the rigorous analysis of the 21 cm power spectrum and for the maximal isolation of the "EoR window" from foreground contamination. We present a method to infer the covariance of foreground residuals from the data itself in contrast to previous attempts at a priori modeling. We demonstrate our method by setting limits on the power spectrum using a 3 h integration from the 128-tile Murchison Widefield Array. Observing between 167 and 198 MHz, we find at 95% confidence a best limit of Delta^2(k) < 3.7 x 10^4 mK^2 at comoving scale k = 0.18 hMpc^-1 and at z = 6.8, consistent with existing limits.
Keywords
Cite
@article{arxiv.1506.01026,
title = {Empirical Covariance Modeling for 21 cm Power Spectrum Estimation: A Method Demonstration and New Limits from Early Murchison Widefield Array 128-Tile Data},
author = {Joshua S. Dillon and Abraham R. Neben and Jacqueline N. Hewitt and Max Tegmark and N. Barry and A. P. Beardsley and J. D. Bowman and F. Briggs and P. Carroll and A. de Oliveira-Costa and A. Ewall-Wice and L. Feng and L. J. Greenhill and B. J. Hazelton and L. Hernquist and N. Hurley-Walker and D. C. Jacobs and H. S. Kim and P. Kittiwisit and E. Lenc and J. Line and A. Loeb and B. McKinley and D. A. Mitchell and M. F. Morales and A. R. Offringa and S. Paul and B. Pindor and J. C. Pober and P. Procopio and J. Riding and S. Sethi and N. Udaya Shankar and R. Subrahmanyan and I. Sullivan and Nithyanandan Thyagarajan and S. J. Tingay and C. Trott and R. B. Wayth and R. L. Webster and S. Wyithe and G. Bernardi and R. J. Cappallo and A. A. Deshpande and M. Johnston-Hollitt and D. L. Kaplan and C. J. Lonsdale and S. R. McWhirter and E. Morgan and D. Oberoi and S. M. Ord and T. Prabu and K. S. Srivani and A. Williams and C. L. Williams},
journal= {arXiv preprint arXiv:1506.01026},
year = {2016}
}
Comments
18 pages, 9 figures. Accepted to Phys. Rev. D