Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array
Structure imprinted in foreground extragalactic point sources by ionospheric refraction has the potential to contaminate Epoch of Reionization (EoR) power spectra of the 21 cm emission line of neutral hydrogen. The alteration of the spatial and spectral structure of foreground measurements due to to...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
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American Astronomical Society
2019
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| Online Access: | https://hdl.handle.net/1721.1/121434 |
| _version_ | 1826213267334234112 |
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| author | Trott, Cathryn M. Jordan, C. H. Murray, S. G. Pindor, B. Mitchell, D. A. Wayth, R. B. Line, J. McKinley, B. Beardsley, A. Bowman, J. Briggs, F. Hazelton, B. J. Hewitt, Jacqueline N Jacobs, D. Morales, M. F. Pober, J. C. Sethi, S. Shankar, U. Subrahmanyan, R. Tegmark, M. Tingay, S. J. Webster, R. L. Wyithe, J. S. B. |
| author2 | MIT Kavli Institute for Astrophysics and Space Research |
| author_facet | MIT Kavli Institute for Astrophysics and Space Research Trott, Cathryn M. Jordan, C. H. Murray, S. G. Pindor, B. Mitchell, D. A. Wayth, R. B. Line, J. McKinley, B. Beardsley, A. Bowman, J. Briggs, F. Hazelton, B. J. Hewitt, Jacqueline N Jacobs, D. Morales, M. F. Pober, J. C. Sethi, S. Shankar, U. Subrahmanyan, R. Tegmark, M. Tingay, S. J. Webster, R. L. Wyithe, J. S. B. |
| author_sort | Trott, Cathryn M. |
| collection | MIT |
| description | Structure imprinted in foreground extragalactic point sources by ionospheric refraction has the potential to contaminate Epoch of Reionization (EoR) power spectra of the 21 cm emission line of neutral hydrogen. The alteration of the spatial and spectral structure of foreground measurements due to total electron content gradients in the ionosphere creates a departure from the expected sky signal. We present a general framework for understanding the signatures of ionospheric behavior in the 2D neutral hydrogen power spectrum measured by a low-frequency radio interferometer. Two primary classes of ionospheric behavior are considered, corresponding to dominant modes observed in Murchison Widefield Array (MWA) EoR data, namely, anisotropic structured wave behavior and isotropic turbulence. Analytic predictions for power spectrum bias due to this contamination are computed and compared with simulations. We then apply the ionospheric metric described in Jordan et al. to study the impact of ionospheric structure on MWA data, by dividing MWA EoR data sets into classes with good and poor ionospheric conditions, using sets of matched 30-minute observations from 2014 September. The results are compared with the analytic and simulated predictions, demonstrating the observed bias in the power spectrum when the ionosphere is active (displays coherent structures or isotropic turbulence). The analysis demonstrates that unless ionospheric activity can be quantified and corrected, active data should not be included in EoR analysis in order to avoid systematic biases in cosmological power spectra. When data are corrected with a model formed from the calibration information, bias reduces below the expected 21 cm signal level. Data are considered "quiet" when the median measured source position offsets are less than 10farcs–15farcs |
| first_indexed | 2024-09-23T15:46:21Z |
| format | Article |
| id | mit-1721.1/121434 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T15:46:21Z |
| publishDate | 2019 |
| publisher | American Astronomical Society |
| record_format | dspace |
| spelling | mit-1721.1/1214342022-09-29T16:03:10Z Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array Trott, Cathryn M. Jordan, C. H. Murray, S. G. Pindor, B. Mitchell, D. A. Wayth, R. B. Line, J. McKinley, B. Beardsley, A. Bowman, J. Briggs, F. Hazelton, B. J. Hewitt, Jacqueline N Jacobs, D. Morales, M. F. Pober, J. C. Sethi, S. Shankar, U. Subrahmanyan, R. Tegmark, M. Tingay, S. J. Webster, R. L. Wyithe, J. S. B. MIT Kavli Institute for Astrophysics and Space Research Structure imprinted in foreground extragalactic point sources by ionospheric refraction has the potential to contaminate Epoch of Reionization (EoR) power spectra of the 21 cm emission line of neutral hydrogen. The alteration of the spatial and spectral structure of foreground measurements due to total electron content gradients in the ionosphere creates a departure from the expected sky signal. We present a general framework for understanding the signatures of ionospheric behavior in the 2D neutral hydrogen power spectrum measured by a low-frequency radio interferometer. Two primary classes of ionospheric behavior are considered, corresponding to dominant modes observed in Murchison Widefield Array (MWA) EoR data, namely, anisotropic structured wave behavior and isotropic turbulence. Analytic predictions for power spectrum bias due to this contamination are computed and compared with simulations. We then apply the ionospheric metric described in Jordan et al. to study the impact of ionospheric structure on MWA data, by dividing MWA EoR data sets into classes with good and poor ionospheric conditions, using sets of matched 30-minute observations from 2014 September. The results are compared with the analytic and simulated predictions, demonstrating the observed bias in the power spectrum when the ionosphere is active (displays coherent structures or isotropic turbulence). The analysis demonstrates that unless ionospheric activity can be quantified and corrected, active data should not be included in EoR analysis in order to avoid systematic biases in cosmological power spectra. When data are corrected with a model formed from the calibration information, bias reduces below the expected 21 cm signal level. Data are considered "quiet" when the median measured source position offsets are less than 10farcs–15farcs 2019-06-27T18:04:53Z 2019-06-27T18:04:53Z 2018-10 2018-09 2019-03-26T17:03:46Z Article http://purl.org/eprint/type/JournalArticle 1538-4357 https://hdl.handle.net/1721.1/121434 Trott, Cathryn M. et al. “Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array.” The Astrophysical Journal 867, 1 (October 2018): 15 http://dx.doi.org/10.3847/1538-4357/AAE314 Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Astronomical Society The Astrophysical Journal |
| spellingShingle | Trott, Cathryn M. Jordan, C. H. Murray, S. G. Pindor, B. Mitchell, D. A. Wayth, R. B. Line, J. McKinley, B. Beardsley, A. Bowman, J. Briggs, F. Hazelton, B. J. Hewitt, Jacqueline N Jacobs, D. Morales, M. F. Pober, J. C. Sethi, S. Shankar, U. Subrahmanyan, R. Tegmark, M. Tingay, S. J. Webster, R. L. Wyithe, J. S. B. Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array |
| title | Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array |
| title_full | Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array |
| title_fullStr | Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array |
| title_full_unstemmed | Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array |
| title_short | Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array |
| title_sort | assessment of ionospheric activity tolerances for epoch of reionization science with the murchison widefield array |
| url | https://hdl.handle.net/1721.1/121434 |
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