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151. 'Grammatical Sense' As a Factor in Reading Comprehension.

Author: Briggs, F. Allen
Abstract: The function of syntax as a factor in comprehension is described in terms of transformations of basic sentence patterns. Examples of transformations of the basic indirect object sentence are included to show emphasis, questions, negations, and coordinate or subordinate relationships. The term grammeme is defined as the minimum unit of syntactical significance used in communication. It is recommended that these syntactical patterns and the accompaying concepts they convey, along with semantic understanding of morphemes, be taught as part of reading instruction. (CM)
Published: 1968

152. Parametrizing Epoch of Reionization foregrounds: a deep survey of low-frequency point-source spectra with the Murchison Widefield Array

Author: Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Hewitt, Jacqueline N, Neben, Abraham Richard, Tegmark, Max Erik, Offringa, A. R., Trott, C. M., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Jacobs, D. C., Kim, H.-S., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D. A., Morales, M. F., Paul, S., Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sethi, S. K., Shankar, N. U., Subrahmanyan, R., Sullivan, I. S., Thyagarajan, N., Tingay, S. J., Wayth, R. B., Webster, R. L., Wyithe, J. S. B., Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Hewitt, Jacqueline N, Neben, Abraham Richard, Tegmark, Max Erik, Offringa, A. R., Trott, C. M., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Jacobs, D. C., Kim, H.-S., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D. A., Morales, M. F., Paul, S., Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sethi, S. K., Shankar, N. U., Subrahmanyan, R., Sullivan, I. S., Thyagarajan, N., Tingay, S. J., Wayth, R. B., Webster, R. L., and Wyithe, J. S. B.
Abstract: Experiments that pursue detection of signals from the Epoch of Reionization (EoR) are relying on spectral smoothness of source spectra at low frequencies. This article empirically explores the effect of foreground spectra on EoR experiments by measuring high-resolution full-polarization spectra for the 586 brightest unresolved sources in one of the Murchison Widefield Array (MWA) EoR fields using 45 h of observation. A novel peeling scheme is used to subtract 2500 sources from the visibilities with ionospheric and beam corrections, resulting in the deepest, confusion-limited MWA image so far. The resulting spectra are found to be affected by instrumental effects, which limit the constraints that can be set on source-intrinsic spectral structure. The sensitivity and power-spectrum of the spectra are analysed, and it is found that the spectra of residuals are dominated by point spread function sidelobes from nearby undeconvolved sources. We release a catalogue describing the spectral parameters for each measured source.
Published: 2017

153. THE IMPORTANCE OF WIDE-FIELD FOREGROUND REMOVAL FOR 21 cm COSMOLOGY: A DEMONSTRATION WITH EARLY MWA EPOCH OF REIONIZATION OBSERVATIONS

Author: Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Cappallo, Roger J, Corey, Brian E, de Oliveira Costa, Angelica, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Kratzenberg, Eric W, Lonsdale, Colin John, McWhirter, Stephen R., Morgan, Edward H, Rogers, Alan E E, Whitney, Alan R, Pober, J. C., Hazelton, B. J., Beardsley, A. P., Barry, N. A., Martinot, Z. E., Sullivan, I. S., Morales, M. F., Bell, M. E., Bernardi, G., Bhat, N. D. R., Bowman, J. D., Briggs, F., Carroll, P., Deshpande, A. A., Dillon, Joshua S., Emrich, D., Ewall-Wice, A. M., Greenhill, L. J., Hindson, L., Hurley-Walker, N., Jacobs, D. C., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kim, Han-Seek, Kittiwisit, P., Kudryavtseva, N., Lenc, E., Line, J., Loeb, A., Lynch, M. J., McKinley, B., Mitchell, D. A., Neben, A. R., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, Sourabh, Pindor, B., Prabu, T., Procopio, P., Riding, J., Roshi, A., Sethi, Shiv K., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tegmark, M., Thyagarajan, Nithyanandan, Tingay, S. J., Trott, C. M., Waterson, M., Wayth, R. B., Webster, R. L., Williams, A., Williams, C. L., Wyithe, J. S. B., Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Cappallo, Roger J, Corey, Brian E, de Oliveira Costa, Angelica, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Kratzenberg, Eric W, Lonsdale, Colin John, McWhirter, Stephen R., Morgan, Edward H, Rogers, Alan E E, Whitney, Alan R, Pober, J. C., Hazelton, B. J., Beardsley, A. P., Barry, N. A., Martinot, Z. E., Sullivan, I. S., Morales, M. F., Bell, M. E., Bernardi, G., Bhat, N. D. R., Bowman, J. D., Briggs, F., Carroll, P., Deshpande, A. A., Dillon, Joshua S., Emrich, D., Ewall-Wice, A. M., Greenhill, L. J., Hindson, L., Hurley-Walker, N., Jacobs, D. C., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kim, Han-Seek, Kittiwisit, P., Kudryavtseva, N., Lenc, E., Line, J., Loeb, A., Lynch, M. J., McKinley, B., Mitchell, D. A., Neben, A. R., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, Sourabh, Pindor, B., Prabu, T., Procopio, P., Riding, J., Roshi, A., Sethi, Shiv K., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tegmark, M., Thyagarajan, Nithyanandan, Tingay, S. J., Trott, C. M., Waterson, M., Wayth, R. B., Webster, R. L., Williams, A., Williams, C. L., and Wyithe, J. S. B.
Abstract: In this paper we present observations, simulations, and analysis demonstrating the direct connection between the location of foreground emission on the sky and its location in cosmological power spectra from interferometric redshifted 21 cm experiments. We begin with a heuristic formalism for understanding the mapping of sky coordinates into the cylindrically averaged power spectra measurements used by 21 cm experiments, with a focus on the effects of the instrument beam response and the associated sidelobes. We then demonstrate this mapping by analyzing power spectra with both simulated and observed data from the Murchison Widefield Array. We find that removing a foreground model that includes sources in both the main field of view and the first sidelobes reduces the contamination in high k[subscript ∥] modes by several per cent relative to a model that only includes sources in the main field of view, with the completeness of the foreground model setting the principal limitation on the amount of power removed. While small, a percent-level amount of foreground power is in itself more than enough to prevent recovery of any Epoch of Reionization signal from these modes. This result demonstrates that foreground subtraction for redshifted 21 cm experiments is truly a wide-field problem, and algorithms and simulations must extend beyond the instrument's main field of view to potentially recover the full 21 cm power spectrum.
Published: 2017

154. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Author: Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Greenhill, Lincoln J, Hewitt, Jacqueline N, Loeb, A., Neben, Abraham Richard, Tegmark, Max Erik, Morgan, Edward H, Williams, Christopher Leigh, Kapińska, A. D., Staveley-Smith, L., Crocker, R., Meurer, G. R., Bhandari, S., Hurley-Walker, N., Offringa, A. R., Hanish, D. J., Seymour, N., Ekers, R. D., Bell, M. E., Callingham, J. R., Dwarakanath, K. S., For, B.-Q., Gaensler, B. M., Hancock, P. J., Hindson, L., Johnston-Hollitt, M., Lenc, E., McKinley, B., Morgan, J., Procopio, P., Wayth, R. B., Wu, C., Zheng, Q., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Hazelton, B. J., Jacobs, D. J., Kim, H.-S., Kittiwisit, P., Line, J., Mitchell, D. A., Morales, M. F., Paul, S., Pindor, B., Pober, J. C., Riding, J., Sethi, S. K., Shankar, N. Udaya, Subrahmanyan, R., Sullivan, I. S., Thyagarajan, N., Tingay, S. J., Trott, C. M., Webster, R. L., Wyithe, S. B., Cappallo, R. J., Deshpande, A. A., Kaplan, D. L., Lonsdale, C. J., McWhirter, S. R., Oberoi, D., Ord, S. M., Prabu, T., Srivani, K. S., Williams, A., Greenhill, Lincoln J., Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Greenhill, Lincoln J, Hewitt, Jacqueline N, Loeb, A., Neben, Abraham Richard, Tegmark, Max Erik, Morgan, Edward H, Williams, Christopher Leigh, Kapińska, A. D., Staveley-Smith, L., Crocker, R., Meurer, G. R., Bhandari, S., Hurley-Walker, N., Offringa, A. R., Hanish, D. J., Seymour, N., Ekers, R. D., Bell, M. E., Callingham, J. R., Dwarakanath, K. S., For, B.-Q., Gaensler, B. M., Hancock, P. J., Hindson, L., Johnston-Hollitt, M., Lenc, E., McKinley, B., Morgan, J., Procopio, P., Wayth, R. B., Wu, C., Zheng, Q., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Hazelton, B. J., Jacobs, D. J., Kim, H.-S., Kittiwisit, P., Line, J., Mitchell, D. A., Morales, M. F., Paul, S., Pindor, B., Pober, J. C., Riding, J., Sethi, S. K., Shankar, N. Udaya, Subrahmanyan, R., Sullivan, I. S., Thyagarajan, N., Tingay, S. J., Trott, C. M., Webster, R. L., Wyithe, S. B., Cappallo, R. J., Deshpande, A. A., Kaplan, D. L., Lonsdale, C. J., McWhirter, S. R., Oberoi, D., Ord, S. M., Prabu, T., Srivani, K. S., Williams, A., and Greenhill, Lincoln J.
Abstract: We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free–free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154–231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ~8 kpc in the z-direction (from the major axis).
Published: 2017

155. LOW-FREQUENCY OBSERVATIONS OF LINEARLY POLARIZED STRUCTURES IN THE INTERSTELLAR MEDIUM NEAR THE SOUTH GALACTIC POLE

Author: Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Cappallo, Roger J, Corey, Brian E, de Oliveira Costa, Angelica, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Morgan, Edward H, Neben, Abraham Richard, Rogers, Alan E E, Tegmark, Max Erik, Whitney, Alan R, Williams, Christopher Leigh, Lenc, E., Gaensler, B. M., Sun, X. H., Sadler, E. M., Willis, A. G., Barry, N., Beardsley, A. P., Bell, M. E., Bernardi, G., Bowman, J. D., Briggs, F., Callingham, J. R., Carroll, P., Deshpande, A. A., Dwarkanath, K. S., Emrich, D., For, B.-Q., Greenhill, L. J., Hancock, P., Hazelton, B. J., Hindson, L., Hurley-Walker, N., Johnston-Hollitt, M., Jacobs, D. C., Kapińska, A. D., Kaplan, D. L., Kasper, J. C., Kim, H.-S., Kratzenberg, E., Line, J., Loeb, A., Lonsdale, C. J., Lynch, M. J., McKinley, B., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, J., Murphy, T., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, S., Pindor, B., Pober, J. C., Prabu, T., Procopio, P., Riding, J., Roshi, A., Shankar, N. Udaya, Sethi, S. K., Srivani, K. S., Staveley-Smith, L., Subrahmanyan, R., Sullivan, I. S., Thyagarajan, Nithyanandan, Tingay, S. J., Trott, C., Waterson, M., Wayth, R. B., Webster, R. L., Williams, A., Wu, C., Wyithe, J. S. B., Zheng, Q., Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Cappallo, Roger J, Corey, Brian E, de Oliveira Costa, Angelica, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Morgan, Edward H, Neben, Abraham Richard, Rogers, Alan E E, Tegmark, Max Erik, Whitney, Alan R, Williams, Christopher Leigh, Lenc, E., Gaensler, B. M., Sun, X. H., Sadler, E. M., Willis, A. G., Barry, N., Beardsley, A. P., Bell, M. E., Bernardi, G., Bowman, J. D., Briggs, F., Callingham, J. R., Carroll, P., Deshpande, A. A., Dwarkanath, K. S., Emrich, D., For, B.-Q., Greenhill, L. J., Hancock, P., Hazelton, B. J., Hindson, L., Hurley-Walker, N., Johnston-Hollitt, M., Jacobs, D. C., Kapińska, A. D., Kaplan, D. L., Kasper, J. C., Kim, H.-S., Kratzenberg, E., Line, J., Loeb, A., Lonsdale, C. J., Lynch, M. J., McKinley, B., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, J., Murphy, T., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, S., Pindor, B., Pober, J. C., Prabu, T., Procopio, P., Riding, J., Roshi, A., Shankar, N. Udaya, Sethi, S. K., Srivani, K. S., Staveley-Smith, L., Subrahmanyan, R., Sullivan, I. S., Thyagarajan, Nithyanandan, Tingay, S. J., Trott, C., Waterson, M., Wayth, R. B., Webster, R. L., Williams, A., Wu, C., Wyithe, J. S. B., and Zheng, Q.
Published: 2017

156. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Author: Kapińska, AD, Staveley-Smith, L, Crocker, R, Meurer, GR, Bhandari, S, Hurley-Walker, N, Offringa, AR, Hanish, DJ, Seymour, N, Ekers, RD, Bell, ME, Callingham, JR, Dwarakanath, KS, For, BQ, Gaensler, BM, Hancock, PJ, Hindson, L, Johnston-Hollitt, M, Lenc, E, McKinley, B, Morgan, J, Procopio, P, Wayth, RB, Wu, C, Zheng, Q, Barry, N, Beardsley, AP, Bowman, JD, Briggs, F, Carroll, P, Dillon, JS, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Jacobs, DJ, Kim, HS, Kittiwisit, P, Line, J, Loeb, A, Mitchell, DA, Morales, MF, Neben, AR, Paul, S, Pindor, B, Pober, JC, Riding, J, Sethi, SK, Shankar, NU, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Thyagarajan, N, Tingay, SJ, Trott, CM, Webster, RL, Wyithe, SB, Cappallo, RJ, Deshpande, AA, Kaplan, DL, Lonsdale, CJ, McWhirter, SR, Morgan, E, Oberoi, D, Ord, SM, Prabu, T, Srivani, KS, Williams, A, Williams, CL, Kapińska, AD, Staveley-Smith, L, Crocker, R, Meurer, GR, Bhandari, S, Hurley-Walker, N, Offringa, AR, Hanish, DJ, Seymour, N, Ekers, RD, Bell, ME, Callingham, JR, Dwarakanath, KS, For, BQ, Gaensler, BM, Hancock, PJ, Hindson, L, Johnston-Hollitt, M, Lenc, E, McKinley, B, Morgan, J, Procopio, P, Wayth, RB, Wu, C, Zheng, Q, Barry, N, Beardsley, AP, Bowman, JD, Briggs, F, Carroll, P, Dillon, JS, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Jacobs, DJ, Kim, HS, Kittiwisit, P, Line, J, Loeb, A, Mitchell, DA, Morales, MF, Neben, AR, Paul, S, Pindor, B, Pober, JC, Riding, J, Sethi, SK, Shankar, NU, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Thyagarajan, N, Tingay, SJ, Trott, CM, Webster, RL, Wyithe, SB, Cappallo, RJ, Deshpande, AA, Kaplan, DL, Lonsdale, CJ, McWhirter, SR, Morgan, E, Oberoi, D, Ord, SM, Prabu, T, Srivani, KS, Williams, A, and Williams, CL
Abstract: © 2017. The American Astronomical Society. All rights reserved. We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free-free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154-231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z-direction (from the major axis).
Published: 2017

157. Wavelet-based Characterization of Small-scale Solar Emission Features at Low Radio Frequencies

Author: Haystack Observatory, Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Pankratius, Victor, Lonsdale, Colin John, Cappallo, Roger J, Corey, Brian E, Kratzenberg, Eric W, McWhirter, Stephen R., Morgan, Edward H, Williams, Christopher Leigh, Suresh, A., Sharma, R., Oberoi, D., Das, S. B., Timar, B., Bowman, J. D., Briggs, F., Deshpande, A. A., Emrich, D., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Lynch, M. J., Mitchell, D. A., Morales, M. F., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Haystack Observatory, Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Pankratius, Victor, Lonsdale, Colin John, Cappallo, Roger J, Corey, Brian E, Kratzenberg, Eric W, McWhirter, Stephen R., Morgan, Edward H, Williams, Christopher Leigh, Suresh, A., Sharma, R., Oberoi, D., Das, S. B., Timar, B., Bowman, J. D., Briggs, F., Deshpande, A. A., Emrich, D., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Lynch, M. J., Mitchell, D. A., Morales, M. F., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., and Williams, A.
Abstract: Low radio frequency solar observations using the Murchison Widefield Array have recently revealed the presence of numerous weak short-lived narrowband emission features, even during moderately quiet solar conditions. These nonthermal features occur at rates of many thousands per hour in the 30.72 MHz observing bandwidth, and hence necessarily require an automated approach for their detection and characterization. Here, we employ continuous wavelet transform using a mother Ricker wavelet for feature detection from the dynamic spectrum. We establish the efficacy of this approach and present the first statistically robust characterization of the properties of these features. In particular, we examine distributions of their peak flux densities, spectral spans, temporal spans, and peak frequencies. We can reliably detect features weaker than 1 SFU, making them, to the best of our knowledge, the weakest bursts reported in literature. The distribution of their peak flux densities follows a power law with an index of -2.23 in the 12-155 SFU range, implying that they can provide an energetically significant contribution to coronal and chromospheric heating. These features typically last for 1-2 s and possess bandwidths of about 4-5 MHz. Their occurrence rate remains fairly flat in the 140-210 MHz frequency range. At the time resolution of the data, they appear as stationary bursts, exhibiting no perceptible frequency drift. These features also appear to ride on a broadband background continuum, hinting at the likelihood of them being weak type-I bursts.
Published: 2017

158. Measuring phased-array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137 MHz ORBCOMM satellites

Author: Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Neben, Abraham Richard, Hewitt, Jacqueline N, Goeke, Robert F, Lonsdale, Colin John, McWhirter, Stephen R., Williams, Christopher Leigh, Bradley, R. F., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Deshpande, A. A., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Webster, R. L., Williams, A., Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Neben, Abraham Richard, Hewitt, Jacqueline N, Goeke, Robert F, Lonsdale, Colin John, McWhirter, Stephen R., Williams, Christopher Leigh, Bradley, R. F., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Deshpande, A. A., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Webster, R. L., and Williams, A.
Abstract: Detection of the fluctuations in a 21 cm line emission from neutral hydrogen during the Epoch of Reionization in thousand hour integrations poses stringent requirements on calibration and image quality, both of which necessitate accurate primary beam models. The Murchison Widefield Array (MWA) uses phased-array antenna elements which maximize collecting area at the cost of complexity. To quantify their performance, we have developed a novel beam measurement system using the 137 MHz ORBCOMM satellite constellation and a reference dipole antenna. Using power ratio measurements, we measure the in situ beampattern of the MWA antenna tile relative to that of the reference antenna, canceling the variation of satellite flux or polarization with time. We employ angular averaging to mitigate multipath effects (ground scattering) and assess environmental systematics with a null experiment in which the MWA tile is replaced with a second-reference dipole. We achieve beam measurements over 30 dB dynamic range in beam sensitivity over a large field of view (65% of the visible sky), far wider and deeper than drift scans through astronomical sources allow. We verify an analytic model of the MWA tile at this frequency within a few percent statistical scatter within the full width at half maximum. Toward the edges of the main lobe and in the sidelobes, we measure tens of percent systematic deviations. We compare these errors with those expected from known beamforming errors., National Science Foundation (U.S.) (AST-0821321), National Science Foundation (U.S.) (AST-0457585), National Science Foundation (U.S.) (PHY-0835713), National Science Foundation (U.S.) (CAREER-0847753), National Science Foundation (U.S.) (AST-0908884), United States. Air Force Office of Scientific Research (FA9550-0510247)
Published: 2017

159. A high reliability survey of discrete Epoch of Reionization foreground sources in the MWA EoR0 field

Author: Haystack Observatory, Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Cappallo, Roger J, Corey, Brian E, de Oliveira Costa, Angelica, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Kratzenberg, Eric W, Lonsdale, Colin John, McWhirter, Stephen R., Morgan, Edward H, Neben, Abraham Richard, Rogers, Alan E E, Tegmark, Max Erik, Whitney, Alan R, Williams, Christopher Leigh, Carroll, P. A., Line, J., Morales, M. F., Barry, N., Beardsley, A. P., Hazelton, B. J., Jacobs, D. C., Pober, J. C., Sullivan, I. S., Webster, R. L., Bernardi, G., Bowman, J. D., Briggs, F., Emrich, D., Gaensler, B. M., Greenhill, L. J., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kim, HS., Lenc, E., Loeb, A., Lynch, M. J., McKinley, B., Mitchell, D. A., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, S., Pindor, B., Prabu, T., Procopio, P., Riding, J., Roshi, A., Shankar, N. Udaya, Sethi, S. K., Srivani, K. S., Subrahmanyan, R., Thyagarajan, Nithyanandan, Tingay, S. J., Waterson, M., Wayth, R. B., Williams, A., Wu, C., Wyithe, J. S. B., Haystack Observatory, Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Cappallo, Roger J, Corey, Brian E, de Oliveira Costa, Angelica, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Kratzenberg, Eric W, Lonsdale, Colin John, McWhirter, Stephen R., Morgan, Edward H, Neben, Abraham Richard, Rogers, Alan E E, Tegmark, Max Erik, Whitney, Alan R, Williams, Christopher Leigh, Carroll, P. A., Line, J., Morales, M. F., Barry, N., Beardsley, A. P., Hazelton, B. J., Jacobs, D. C., Pober, J. C., Sullivan, I. S., Webster, R. L., Bernardi, G., Bowman, J. D., Briggs, F., Emrich, D., Gaensler, B. M., Greenhill, L. J., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kim, HS., Lenc, E., Loeb, A., Lynch, M. J., McKinley, B., Mitchell, D. A., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, S., Pindor, B., Prabu, T., Procopio, P., Riding, J., Roshi, A., Shankar, N. Udaya, Sethi, S. K., Srivani, K. S., Subrahmanyan, R., Thyagarajan, Nithyanandan, Tingay, S. J., Waterson, M., Wayth, R. B., Williams, A., Wu, C., and Wyithe, J. S. B.
Abstract: Detection of the epoch of reionization H i signal requires a precise understanding of the intervening galaxies and AGN, both for instrumental calibration and foreground removal. We present a catalogue of 7394 extragalactic sources at 182 MHz detected in the RA = 0 field of the Murchison Widefield Array Epoch of Reionization observation programme. Motivated by unprecedented requirements for precision and reliability we develop new methods for source finding and selection. We apply machine learning methods to self-consistently classify the relative reliability of 9490 source candidates. A subset of 7466 are selected based on reliability class and signal-to-noise ratio criteria. These are statistically cross-matched to four other radio surveys using both position and flux density information. We find 7369 sources to have confident matches, including 90 partially resolved sources that split into a total of 192 sub-components. An additional 25 unmatched sources are included as new radio detections. The catalogue sources have a median spectral index of −0.85. Spectral flattening is seen towards lower frequencies with a median of −0.71 predicted at 182 MHz. The astrometric error is 7 arcsec compared to a 2.3 arcmin beam FWHM. The resulting catalogue covers ∼1400 deg² and is complete to approximately 80 mJy within half beam power. This provides the most reliable discrete source sky model available to date in the MWA EoR0 field for precision foreground subtraction., National Science Foundation (U.S.) (AST-0847753), National Science Foundation (U.S.) (AST-1410484), National Science Foundation (U.S.) (AST-1506024)
Published: 2017

160. Wavelet-based Characterization of Small-scale Solar Emission Features at Low Radio Frequencies

Author: Suresh, A., Sharma, R., Oberoi, D., Das, S., Pankratius, V., Timar, B., Lonsdale, C., Bowman, J., Briggs, F., Cappallo, R., Corey, B., Deshpande, A., Emrich, David, Goeke, R., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kratzenberg, E., Lynch, Mervyn, McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Ord, S., Prabu, T., Rogers, A., Roshi, A., Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, Anne, Williams, C., Suresh, A., Sharma, R., Oberoi, D., Das, S., Pankratius, V., Timar, B., Lonsdale, C., Bowman, J., Briggs, F., Cappallo, R., Corey, B., Deshpande, A., Emrich, David, Goeke, R., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kratzenberg, E., Lynch, Mervyn, McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Ord, S., Prabu, T., Rogers, A., Roshi, A., Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, Anne, and Williams, C.
Abstract: Low radio frequency solar observations using the Murchison Widefield Array have recently revealed the presence of numerous weak short-lived narrowband emission features, even during moderately quiet solar conditions. These nonthermal features occur at rates of many thousands per hour in the 30.72 MHz observing bandwidth, and hence necessarily require an automated approach for their detection and characterization. Here, we employ continuous wavelet transform using a mother Ricker wavelet for feature detection from the dynamic spectrum. We establish the efficacy of this approach and present the first statistically robust characterization of the properties of these features. In particular, we examine distributions of their peak flux densities, spectral spans, temporal spans, and peak frequencies. We can reliably detect features weaker than 1 SFU, making them, to the best of our knowledge, the weakest bursts reported in literature. The distribution of their peak flux densities follows a power law with an index of -2.23 in the 12-155 SFU range, implying that they can provide an energetically significant contribution to coronal and chromospheric heating. These features typically last for 1-2 s and possess bandwidths of about 4-5 MHz. Their occurrence rate remains fairly flat in the 140-210 MHz frequency range. At the time resolution of the data, they appear as stationary bursts, exhibiting no perceptible frequency drift. These features also appear to ride on a broadband background continuum, hinting at the likelihood of them being weak type-I bursts.
Published: 2017

161. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Author: Kapinska, A., Staveley-Smith, L., Crocker, R., Meurer, G., Bhandari, S., Hurley-Walker, Natasha, Offringa, A., Hanish, D., Seymour, Nick, Ekers, R., Bell, M., Callingham, J., Dwarakanath, K., For, B., Gaensler, B., Hancock, Paul, Hindson, L., Johnston-Hollitt, M., Lenc, E., McKinley, B., Morgan, John, Procopio, P., Wayth, Randall, Wu, C., Zheng, Q., Barry, N., Beardsley, A., Bowman, J., Briggs, F., Carroll, P., Dillon, J., Ewall-Wice, A., Feng, L., Greenhill, L., Hazelton, B., Hewitt, J., Jacobs, D., Kim, H., Kittiwisit, P., Line, J., Loeb, A., Mitchell, D., Morales, M., Neben, A., Paul, S., Pindor, B., Pober, J., Riding, J., Sethi, S., Shankar, N., Subrahmanyan, R., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, Cathryn, Webster, R., Wyithe, S., Cappallo, R., Deshpande, A., Kaplan, D., Lonsdale, C., McWhirter, S., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Srivani, K., Williams, Andrew, Williams, C., Kapinska, A., Staveley-Smith, L., Crocker, R., Meurer, G., Bhandari, S., Hurley-Walker, Natasha, Offringa, A., Hanish, D., Seymour, Nick, Ekers, R., Bell, M., Callingham, J., Dwarakanath, K., For, B., Gaensler, B., Hancock, Paul, Hindson, L., Johnston-Hollitt, M., Lenc, E., McKinley, B., Morgan, John, Procopio, P., Wayth, Randall, Wu, C., Zheng, Q., Barry, N., Beardsley, A., Bowman, J., Briggs, F., Carroll, P., Dillon, J., Ewall-Wice, A., Feng, L., Greenhill, L., Hazelton, B., Hewitt, J., Jacobs, D., Kim, H., Kittiwisit, P., Line, J., Loeb, A., Mitchell, D., Morales, M., Neben, A., Paul, S., Pindor, B., Pober, J., Riding, J., Sethi, S., Shankar, N., Subrahmanyan, R., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, Cathryn, Webster, R., Wyithe, S., Cappallo, R., Deshpande, A., Kaplan, D., Lonsdale, C., McWhirter, S., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Srivani, K., Williams, Andrew, and Williams, C.
Abstract: We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free-free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154-231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ~8 kpc in the z-direction (from the major axis).
Published: 2017

162. GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey - I. A low-frequency extragalactic catalogue

Author: Hurley-Walker, Natasha, Callingham, J., Hancock, Paul, Franzen, Thomas, Hindson, L., Kapinska, A., Morgan, J., Offringa, A., Wayth, Randall, Wu, C., Zheng, Q., Murphy, T., Bell, M., Dwarakanath, K., For, B., Gaensler, B., Johnston-Hollitt, M., Lenc, E., Procopio, P., Staveley-Smith, L., Ekers, Ronald, Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Greenhill, L., Hazelton, B., Kaplan, D., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Udaya Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Webster, R., Williams, A., Williams, C., Hurley-Walker, Natasha, Callingham, J., Hancock, Paul, Franzen, Thomas, Hindson, L., Kapinska, A., Morgan, J., Offringa, A., Wayth, Randall, Wu, C., Zheng, Q., Murphy, T., Bell, M., Dwarakanath, K., For, B., Gaensler, B., Johnston-Hollitt, M., Lenc, E., Procopio, P., Staveley-Smith, L., Ekers, Ronald, Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Greenhill, L., Hazelton, B., Kaplan, D., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Udaya Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Webster, R., Williams, A., and Williams, C.
Abstract: Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalogue, utilizing the first year of observations. The catalogue covers 24 831 square degrees, over declinations south of +30° and Galactic latitudes outside 10° of the Galactic plane, excluding some areas such as theMagellanic Clouds. It contains 307 455 radio sources with 20 separate flux density measurements across 72-231 MHz, selected from a time- and frequency-integrated image centred at 200 MHz, with a resolution of ˜2 arcmin. Over the catalogued region, we estimate that the catalogue is 90 per cent complete at 170 mJy, and 50 per cent complete at 55 mJy, and large areas are complete at even lower flux density levels. Its reliability is 99.97 per cent above the detection threshold of 5s, which itself is typically 50 mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low-frequency flux density scale of the southern sky to better than 10 per cent. This paper presents details of the flagging, imaging, mosaicking and source extraction/characterization, as well as estimates of the completeness and reliability. All source measurements and images are available online. 1 This is the first in a series of publications describing the GLEAM survey results. © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society
Published: 2017

163. L.M.C. Resolution On Group Practice Loans Fund

Author: Alexander, R., Anniss, D., Blake, H. V., Briggs, F. B., Bryce-Curtis, P. J., Bywater, H. C. I., Caldwell, J. R., Carnegie, G. F. M., Chamberlain-Webber, J. A. A., Christopher, B. W., Collin, J. O., Dart, David E., Dennison, E. J., Dormand, G., Faro, D., Gilkes, M. J., Glenn, R. W., Godwin, D., Gooding, D. J., Gray, P. F., Green, Ralph, Gundersen, G. C., Hall, Michael, Hartley, J. L., Harvey, N. W. A., Hunter, J. D. W., Lodge, R. M., Murdoch, James W., Palmer, C. R., Ruck, Colin, Ryle, F. R., Sibley, E. G., Tulk-Hart, R. B., de C. Veale, W. F., and Wright, J. R.
Published: 1970

164. A large-scale, low-frequency murchison widefield array survey of galactic H II regions between 260 < l < 340

Author: Hindson, L, Johnston-Hollitt, M, Hurley-Walker, N, Callingham, JR, Su, H, Morgan, J, Bell, M, Bernardi, G, Bowman, JD, Briggs, F, Cappallo, RJ, Deshpande, AA, Dwarakanath, KS, For, BQ, Gaensler, BM, Greenhill, LJ, Hancock, P, Hazelton, BJ, Kapinska, AD, Kaplan, DL, Lenc, E, Lonsdale, CJ, Mckinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Oberoi, D, Offringa, A, Ord, SM, Procopio, P, Prabu, T, Udaya Shankar, N, Srivani, KS, Staveley-Smith, L, Subrahmanyan, R, Tingay, SJ, Wayth, RB, Webster, RL, Williams, A, Williams, CL, Wu, C, and Zheng, Q
Subjects: Astronomy & Astrophysics
Abstract: © Astronomical Society of Australia 2016. We have compiled a catalogue of H ii regions detected with the Murchison Widefield Array between 72 and 231 MHz. The multiple frequency bands provided by the Murchison Widefield Array allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in H ii regions. We detect 306 H ii regions between 260◦ < l < 340◦ and report on the positions, sizes, peak, integrated flux density, and spectral indices of these H ii regions. By identifying the point at which H ii regions transition from the optically thin to thick regime, we derive the physical properties including the electron density, ionised gas mass, and ionising photon flux, towards 61 H ii regions. This catalogue of H ii regions represents the most extensive and uniform low frequency survey of H ii regions in the Galaxy to date.
Published: 2016

165. Multi-Instance Multi-Label Class Discovery: A Computational Approach for Assessing Bird Biodiversity

Author: Briggs, F., Fern, X. Z., Raich, R., and Matthew Betts
Subjects: General Medicine
Abstract: We study the problem of analyzing a large volume ofbioacoustic data collected in-situ with the goal of assessingthe biodiversity of bird species at the data collectionsite. We are interested in the class discoveryproblem for this setting. Specifically, given a large collectionof audio recordings containing bird and othersounds, we aim to automatically select a fixed size subsetof the recordings for human expert labeling suchthat the maximum number of species/classes is discovered.We employ a multi-instance multi-label representationto address multiple simultaneously vocalizingbirds with sounds that overlap in time, and proposenew algorithms for species/class discovery using thisrepresentation. In a comparative study, we show that theproposed methods discover more species/classes thancurrent state-of-the-art in a real world datasetof 92,095 ten-second recordings collected in field conditions.
Published: 2016
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166. A Large Scale, Low Frequency Murchison Widefield Array Survey of Galactic HII regions between 260< l

Author: Hindson, L., Johnston-Hollitt, M., Hurley-Walker, N., Callingham, J. R., Su, H., Morgan, J., Bell, M., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Deshpande, A. A., Dwarakanath, K. S., For, B. -Q, Gaensler, B. M., Greenhill, L. J., Hancock, P., Hazelton, B. J., Kapinska, A. D., Kaplan, D. L., Lenc, E., Lonsdale, C. J., Mckinley, B., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Offringa, A., Ord, S. M., Procopio, P., Prabu, T., UdayaShankar, N., Srivani, K. S., Staveley-Smith, L., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Webster, R. L., Williams, A., Williams, C. L., Wu, C., and Zheng, Q.
Subjects: Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences
Abstract: We have compiled a catalogue of HII regions detected with the Murchison Widefield Array (MWA) between 72 and 231MHz. The multiple frequency bands provided by the MWA allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in HII regions. We detect 302 HII regions between 260 < l < 340 and report on the positions, sizes, peak, integrated flux density, and spectral indices of these HII regions. By identifying the point at which HII regions transition from the optically thin to thick regime we derive the physical properties including the electron density, ionised gas mass and ionising photon flux, towards 61 HII regions. This catalogue of HII regions represents the most extensive and uniform low frequency survey of HII regions in the Galaxy to date., 20 pages, 9 figures, 3 tables
Published: 2016
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167. Wavelet-based Characterization of Small-scale Solar Emission Features at Low Radio Frequencies

Author: Suresh, A., primary, Sharma, R., additional, Oberoi, D., additional, Das, S. B., additional, Pankratius, V., additional, Timar, B., additional, Lonsdale, C. J., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2017
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168. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Author: Kapińska, A. D., primary, Staveley-Smith, L., additional, Crocker, R., additional, Meurer, G. R., additional, Bhandari, S., additional, Hurley-Walker, N., additional, Offringa, A. R., additional, Hanish, D. J., additional, Seymour, N., additional, Ekers, R. D., additional, Bell, M. E., additional, Callingham, J. R., additional, Dwarakanath, K. S., additional, For, B.-Q., additional, Gaensler, B. M., additional, Hancock, P. J., additional, Hindson, L., additional, Johnston-Hollitt, M., additional, Lenc, E., additional, McKinley, B., additional, Morgan, J., additional, Procopio, P., additional, Wayth, R. B., additional, Wu, C., additional, Zheng, Q., additional, Barry, N., additional, Beardsley, A. P., additional, Bowman, J. D., additional, Briggs, F., additional, Carroll, P., additional, Dillon, J. S., additional, Ewall-Wice, A., additional, Feng, L., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Jacobs, D. J., additional, Kim, H.-S., additional, Kittiwisit, P., additional, Line, J., additional, Loeb, A., additional, Mitchell, D. A., additional, Morales, M. F., additional, Neben, A. R., additional, Paul, S., additional, Pindor, B., additional, Pober, J. C., additional, Riding, J., additional, Sethi, S. K., additional, Shankar, N. Udaya, additional, Subrahmanyan, R., additional, Sullivan, I. S., additional, Tegmark, M., additional, Thyagarajan, N., additional, Tingay, S. J., additional, Trott, C. M., additional, Webster, R. L., additional, Wyithe, S. B., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Kaplan, D. L., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Srivani, K. S., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2017
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169. A Matched Filter Technique for Slow Radio Transient Detection and First Demonstration with the Murchison Widefield Array

Author: Feng, L., primary, Vaulin, R., additional, Hewitt, J. N., additional, Remillard, R., additional, Kaplan, D. L., additional, Murphy, Tara, additional, Kudryavtseva, N., additional, Hancock, P., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Wayth, R. B., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2017
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170. The Cosmic Dawn and Epoch of Reionisation with SKA

Author: Koopmans, L, Pritchard, J, Mellema, G, Aguirre, J, Ahn, K, Barkana, R, van Bemmel, I, Bernardi, A, Bonaldi, A, Briggs, F, de Bruyn, A G, Chang, T C, Chapman, E, Chen, X, Ciardi, B, Dayal, P, Ferrara, A, Fialkov, A, Fiore, F, Ichiki, K, Iliev, I T, et, al., and Organisation, SKA
Subjects: QB
Abstract: Concerted effort is currently ongoing to open up the Epoch of Reionization (z ∼15-6) for studies with IR and radio telescopes. Whereas IR detections have been made of sources (Lyman-α emitters, quasars and drop-outs) in this redshift regime in relatively small fields of view, no direct detection of neutral hydrogen, via the redshifted 21-cm line, has yet been established. Such a direct detection is expected in the coming years, with ongoing surveys, and could open up the entire universe from z ∼6-200 for astrophysical and cosmological studies, opening not only the Epoch of Reionization, but also its preceding Cosmic Dawn (z ∼30-15) and possibly even the later phases of the Dark Ages (z ∼200-30). All currently ongoing experiments attempt statistical detections of the 21-cm signal during the Epoch of Reionization, with limited signal-to-noise. Direct imaging, except maybe on the largest (degree) scales at lower redshifts, as well as higher redshifts will remain out of reach. The Square Kilometre Array (SKA) will revolutionize the field, allowing direct imaging of neutral hydrogen from scales of arc-minutes to degrees over most of the redshift range z ∼6-28 with SKA1-LOW, and possibly even higher redshifts with the SKA2-LOW. In this SKA will be unique, and in parallel provide enormous potential of synergy with other upcoming facilities (e.g. JWST). In this chapter we summarize the physics of 21-cm emission, the different phases the universe is thought to go through, and the observables that the SKA can probe, referring where needed to detailed chapters in this volume. This is done within the framework of the current SKA1 baseline design and a nominal CD/EoR straw-man survey, consisting of a shallow, medium-deep and deep survey, the latter probing down to ∼1 mK brightness temperature on arc-minute scales at the end of reionization. Possible minor modifications to the design of SKA1 and the upgrade to SKA2 are discussed, in addition to science that could be done already during roll-out when SKA1 still has limited capabilities and/or core collecting area.
Published: 2015

171. DELAY SPECTRUM WITH PHASE-TRACKING ARRAYS: EXTRACTING THE H i POWER SPECTRUM FROM THE EPOCH OF REIONIZATION

Author: Paul, Sourabh, primary, Sethi, Shiv K., additional, Morales, Miguel F., additional, Dwarkanath, K. S., additional, Shankar, N. Udaya, additional, Subrahmanyan, Ravi, additional, Barry, N., additional, Beardsley, A. P., additional, Bowman, Judd D., additional, Briggs, F., additional, Carroll, P., additional, de Oliveira-Costa, A., additional, Dillon, Joshua S., additional, Ewall-Wice, A., additional, Feng, L., additional, Greenhill, L. J., additional, Gaensler, B. M., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Hurley-Walker, N., additional, Jacobs, D. J., additional, Kim, Han-Seek, additional, Kittiwisit, P., additional, Lenc, E., additional, Line, J., additional, Loeb, A., additional, McKinley, B., additional, Mitchell, D. A., additional, Neben, A. R., additional, Offringa, A. R., additional, Pindor, B., additional, Pober, J. C., additional, Procopio, P., additional, Riding, J., additional, Sullivan, I. S., additional, Tegmark, M., additional, Thyagarajan, Nithyanandan, additional, Tingay, S. J., additional, Trott, C. M., additional, Wayth, R. B., additional, Webster, R. L., additional, Wyithe, J. S. B., additional, Cappallo, Roger, additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Srivani, K. S., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2016
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172. FIRST SEASON MWA EOR POWER SPECTRUM RESULTS AT REDSHIFT 7

Author: Beardsley, A. P., primary, Hazelton, B. J., additional, Sullivan, I. S., additional, Carroll, P., additional, Barry, N., additional, Rahimi, M., additional, Pindor, B., additional, Trott, C. M., additional, Line, J., additional, Jacobs, Daniel C., additional, Morales, M. F., additional, Pober, J. C., additional, Bernardi, G., additional, Bowman, Judd D., additional, Busch, M. P., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Oliveira-Costa, A. de, additional, Dillon, Joshua S., additional, Emrich, D., additional, Ewall-Wice, A., additional, Feng, L., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hewitt, J. N., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kim, H. S., additional, Kratzenberg, E., additional, Lenc, E., additional, Loeb, A., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morgan, E., additional, Neben, A. R., additional, Thyagarajan, Nithyanandan, additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S. M., additional, Paul, S., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Sethi, Shiv K., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tegmark, M., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, and Wyithe, J. S. B., additional
Published: 2016
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173. Measuring phased-array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137 MHz ORBCOMM satellites

Author: Bradley, R. F., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Deshpande, A. A., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Webster, R. L., Williams, A., Neben, Abraham Richard, Hewitt, Jacqueline N, Goeke, Robert F, Lonsdale, Colin John, McWhirter, Stephen R., Williams, Christopher Leigh, Haystack Observatory, MIT Kavli Institute for Astrophysics and Space Research, Neben, Abraham Richard, Hewitt, Jacqueline N, Goeke, Robert F, Lonsdale, Colin John, McWhirter, Stephen R., and Williams, Christopher Leigh
Subjects: Astrophysics::Instrumentation and Methods for Astrophysics
Abstract: Detection of the fluctuations in a 21 cm line emission from neutral hydrogen during the Epoch of Reionization in thousand hour integrations poses stringent requirements on calibration and image quality, both of which necessitate accurate primary beam models. The Murchison Widefield Array (MWA) uses phased-array antenna elements which maximize collecting area at the cost of complexity. To quantify their performance, we have developed a novel beam measurement system using the 137 MHz ORBCOMM satellite constellation and a reference dipole antenna. Using power ratio measurements, we measure the in situ beampattern of the MWA antenna tile relative to that of the reference antenna, canceling the variation of satellite flux or polarization with time. We employ angular averaging to mitigate multipath effects (ground scattering) and assess environmental systematics with a null experiment in which the MWA tile is replaced with a second-reference dipole. We achieve beam measurements over 30 dB dynamic range in beam sensitivity over a large field of view (65% of the visible sky), far wider and deeper than drift scans through astronomical sources allow. We verify an analytic model of the MWA tile at this frequency within a few percent statistical scatter within the full width at half maximum. Toward the edges of the main lobe and in the sidelobes, we measure tens of percent systematic deviations. We compare these errors with those expected from known beamforming errors., National Science Foundation (U.S.) (AST-0821321), National Science Foundation (U.S.) (AST-0457585), National Science Foundation (U.S.) (PHY-0835713), National Science Foundation (U.S.) (CAREER-0847753), National Science Foundation (U.S.) (AST-0908884), United States. Air Force Office of Scientific Research (FA9550-0510247)
Published: 2015

174. Local galaxies as damped Lyman-$\alpha$ absorber analogues

Author: Zwaan, M. A., van der Hulst, J. M., Briggs, F. H., Verheijen, M. A. W., Ryan-Weber, E. V., Williams, Peter R., Shu, Cheng-Gang, Menard, Brice, and Astronomy
Subjects: Physics, education.field_of_study, Line-of-sight, Number density, Population, Astronomy, Astronomy and Astrophysics, Quasar, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Galaxy, Redshift, law.invention, Telescope, Space and Planetary Science, law, Emission spectrum, education, Astrophysics::Galaxy Astrophysics
Abstract: We calculate in detail the expected properties of low redshift DLAs under the assumption that they arise in the gaseous disks of galaxies like those in the z≈ 0 population. A sample of 355 nearby galaxies were analysed, for which high quality H I 21-cm emission line maps are available as part of an extensive survey with the westerbork telescope (whisp). We find that expected luminosities, impact parameters between quasars and DLA host galaxies, and metal abundances are in good agreement with the observed properties of DLAs and DLA galaxies. The measured redshift number density of z=0 gas above the DLA limit is dn/dz=0.045± 0.006, which compared to higher z measurements implies that there is no evolution in the co-moving density of DLAs along a line of sight between z˜ 1.5 and z=0, and a decrease of only a factor of two from z˜ 4 to the present time. We conclude that the local galaxy population can explain all properties of low redshift DLAs.
Published: 2005
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175. Low-frequency observations of linearly polarized structures in the interstellar medium near the south galactic pole

Author: Lenc, E., Gaensler, B., Sun, X., Sadler, E., Willis, A., Barry, N., Beardsley, A., Bell, M., Bernardi, G., Bowman, J., Briggs, F., Callingham, J., Cappallo, R., Carroll, P., Corey, B., Oliveira-Costa, A., Deshpande, A., Dillon, J., Dwarkanath, K., Emrich, D., Ewall-Wice, A., Feng, L., For, B., Goeke, R., Greenhill, L., Hancock, P., Hazelton, B., Hewitt, J., Hindson, L., Hurley-Walker, N., Johnston-Hollitt, M., Jacobs, D., Kapinska, A., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Line, J., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Morgan, J., Murphy, T., Neben, A., Oberoi, D., Offringa, A., Ord, S., Paul, S., Pindor, B., Pober, J., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Staveley-Smith, L., Subrahmanyan, R., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, C., Waterson, M., Lenc, E., Gaensler, B., Sun, X., Sadler, E., Willis, A., Barry, N., Beardsley, A., Bell, M., Bernardi, G., Bowman, J., Briggs, F., Callingham, J., Cappallo, R., Carroll, P., Corey, B., Oliveira-Costa, A., Deshpande, A., Dillon, J., Dwarkanath, K., Emrich, D., Ewall-Wice, A., Feng, L., For, B., Goeke, R., Greenhill, L., Hancock, P., Hazelton, B., Hewitt, J., Hindson, L., Hurley-Walker, N., Johnston-Hollitt, M., Jacobs, D., Kapinska, A., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Line, J., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Morgan, J., Murphy, T., Neben, A., Oberoi, D., Offringa, A., Ord, S., Paul, S., Pindor, B., Pober, J., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Staveley-Smith, L., Subrahmanyan, R., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, C., and Waterson, M.
Abstract: We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg2 centered on α = 0hand δ = −27°. The sensitivity available in our deep observations allows an in-band, frequency-dependent analysis of polarized structure for the first time at long wavelengths. Our analysis suggests that the polarized structures are dominated by intrinsic emission but may also have a foreground Faraday screen component. At these wavelengths, the compactness of the MWA baseline distribution provides excellent snapshot sensitivity to large-scale structure. The observations are sensitive to diffuse polarized emission at ~54' resolution with a sensitivity of 5.9 mJy beam−1 and compact polarized sources at ~2farcm4 resolution with a sensitivity of 2.3 mJy beam−1 for a subset (400 deg2) of this field. The sensitivity allows the effect of ionospheric Faraday rotation to be spatially and temporally measured directly from the diffuse polarized background. Our observations reveal large-scale structures (~1°–8° in extent) in linear polarization clearly detectable in ~2 minute snapshots, which would remain undetectable by interferometers with minimum baseline lengths of >110 m at 154 MHz. The brightness temperature of these structures is on average 4 K in polarized intensity, peaking at 11 K. Rotation measure synthesis reveals that the structures have Faraday depths ranging from −2 to 10 rad m−2 with a large fraction peaking at approximately +1 rad m−2. We estimate a distance of 51 ± 20 pc to the polarized emission based on measurements of the in-field pulsar J2330–2005. We detect four extragalactic linearly polarized point sources within the field in our compact source survey. Based on the known polarized source population at 1.4 GHz and non-detections at 154 MHz, we estimate an upper limit on the depolarization ratio of 0.08 from 1.4 GHz to 154 MHz.
Published: 2016

176. Time-domain and spectral properties of pulsars at 154 MHz

Author: Bell, M., Murphy, T., Johnston, S., Kaplan, D., Croft, S., Hancock, P., Callingham, J., Zic, A., Dobie, D., Swiggum, J., Rowlinson, A., Hurley-Walker, N., Offringa, A., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Gaensler, B., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Udaya Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Webster, R., Williams, A., Williams, C., Bell, M., Murphy, T., Johnston, S., Kaplan, D., Croft, S., Hancock, P., Callingham, J., Zic, A., Dobie, D., Swiggum, J., Rowlinson, A., Hurley-Walker, N., Offringa, A., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Gaensler, B., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Udaya Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Webster, R., Williams, A., and Williams, C.
Abstract: We present 154 MHz Murchison Widefield Array imaging observations and variability information for a sample of pulsars. Over the declination range −80° < δ < 10°, we detect 17 known pulsars with mean flux density greater than 0.3 Jy. We explore the variability properties of this sample on time-scales of minutes to years. For three of these pulsars, PSR J0953+0755, PSR J0437−4715, and PSR J0630−2834, we observe interstellar scintillation and variability on time-scales of greater than 2 min. One further pulsar, PSR J0034−0721, showed significant variability, the physical origins of which are difficult to determine. The dynamic spectra for PSR J0953+0755 and PSR J0437−4715 show discrete time and frequency structure consistent with diffractive interstellar scintillation and we present the scintillation bandwidth and time-scales from these observations. The remaining pulsars within our sample were statistically non-variable. We also explore the spectral properties of this sample and find spectral curvature in pulsars PSR J0835−4510, PSR J1752−2806, and PSR J0437−4715.
Published: 2016

177. Delay spectrum with phase-tracking arrays: extracting the H I power spectrum from the epoch of reionization

Author: Paul, Sourabh, Sethi, Shiv K., Morales, Miguel F., Dwarkanath, K. S., Shankar, N. Udaya, Subrahmanyan, Ravi, Barry, N., Beardsley, A. P., Bowman, Judd D., Briggs, F., Carroll, P., de Oliveira-Costa, A., Dillon, Joshua, Ewall-Wice, Aaron, Feng, L., Greenhill, L. J., Gaensler, B. M., Hazelton, B. J., Hewitt, J. N., Hurley-Walker, Natasha, Jacobs, D. J., Kim, Han-Seek, Kittiwisit, P., Lenc, E., Line, J., Loeb, A., McKinley, B., Mitchell, D. A., Neben, A. R., Offringa, Andre, Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sullivan, I. S, Tegmark, M., Thyagarajan, Nithyanandan, Tingay, S. J., Trott, C. M., Wayth, R. B., Webster, R. L., Wyithe, J. S. B., Cappallo, Roger, Johnston-Hollitt, M., Kaplan, D. L., Lonsdale, C. J., McWhirter, S. R., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Srivani, K. S., Williams, A., Williams, C. L., Paul, Sourabh, Sethi, Shiv K., Morales, Miguel F., Dwarkanath, K. S., Shankar, N. Udaya, Subrahmanyan, Ravi, Barry, N., Beardsley, A. P., Bowman, Judd D., Briggs, F., Carroll, P., de Oliveira-Costa, A., Dillon, Joshua, Ewall-Wice, Aaron, Feng, L., Greenhill, L. J., Gaensler, B. M., Hazelton, B. J., Hewitt, J. N., Hurley-Walker, Natasha, Jacobs, D. J., Kim, Han-Seek, Kittiwisit, P., Lenc, E., Line, J., Loeb, A., McKinley, B., Mitchell, D. A., Neben, A. R., Offringa, Andre, Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sullivan, I. S, Tegmark, M., Thyagarajan, Nithyanandan, Tingay, S. J., Trott, C. M., Wayth, R. B., Webster, R. L., Wyithe, J. S. B., Cappallo, Roger, Johnston-Hollitt, M., Kaplan, D. L., Lonsdale, C. J., McWhirter, S. R., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Srivani, K. S., Williams, A., and Williams, C. L.
Abstract: The detection of redshifted 21 cm emission from the epoch of reionization (EoR) is a challenging task owing to strong foregrounds that dominate the signal. In this paper, we propose a general method, based on the delay spectrum approach, to extract H i power spectra that are applicable to tracking observations using an imaging radio interferometer ("Delay Spectrum with Imaging Arrays"). Our method is based on modeling the H i signal taking into account the impact of wide field effects such as the w-term, which are then used as appropriate weights in cross-correlating the measured visibilities. Our method is applicable to any radio interferometer that tracks a phase center and could be utilized for arrays such as the Murchison Widefield Array (MWA), Low Frequency Array (LOFAR), Giant Meterwave Radio Telescope (GMRT), Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), and HERA. In the literature the delay spectrum approach has been implemented for near-redundant baselines using drift scan observations. In this paper we explore the scheme for non-redundant tracking arrays. This is the first application of delay spectrum methodology to such data to extract the H i signal. We analyze 3 hr of MWA tracking data on the EoR1 field. We present both two-dimensional (${k}_{\parallel },{k}_{\perp }$) and one-dimensional (k) power spectra from the analysis. Our results are in agreement with the findings of other pipelines developed to analyze the MWA EoR data.
Published: 2016

178. First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating

Author: Ewall-Wice, Aaron, Dillon, Joshua, Hewitt, J. N., Loeb, A., Mesinger, A., Neben, A. R., Offringa, Andre, Tegmark, M., Barry, N., Beardsley, A. P., Bernardi, G., Bowman, Judd D., Briggs, F., Cappallo, R. J., Carroll, P., Corey, B. E., de Oliveira-Costa, A., Emrich, D., Feng, L., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hurley-Walker, Natasha, Johnston-Hollitt, M., Jacobs, Daniel C., Kaplan, D. L., Kasper, J. C., Kim, H. S., Kratzenberg, E., Lenc, E., Line, J., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Thyagarajan, Nithyanandan, Oberoi, D., Ord, S. M., Paul, S., Pindor, B., Pober, J. C., Prabu, T., Procopio, P., Riding, J., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Sethi, Shiv K., Srivani, K. S., Subrahmanyan, R., Sullivan, I. S., Tingay, S. J., Trott, C. M., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Wu, C., Wyithe, J. S. B., McKinley, B., Ewall-Wice, Aaron, Dillon, Joshua, Hewitt, J. N., Loeb, A., Mesinger, A., Neben, A. R., Offringa, Andre, Tegmark, M., Barry, N., Beardsley, A. P., Bernardi, G., Bowman, Judd D., Briggs, F., Cappallo, R. J., Carroll, P., Corey, B. E., de Oliveira-Costa, A., Emrich, D., Feng, L., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hurley-Walker, Natasha, Johnston-Hollitt, M., Jacobs, Daniel C., Kaplan, D. L., Kasper, J. C., Kim, H. S., Kratzenberg, E., Lenc, E., Line, J., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Thyagarajan, Nithyanandan, Oberoi, D., Ord, S. M., Paul, S., Pindor, B., Pober, J. C., Prabu, T., Procopio, P., Riding, J., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Sethi, Shiv K., Srivani, K. S., Subrahmanyan, R., Sullivan, I. S., Tingay, S. J., Trott, C. M., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Wu, C., Wyithe, J. S. B., and McKinley, B.
Abstract: We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). Three hours of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1-3 hours of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of 10 mK⁴ on comoving scales k ≲ 0.5 h Mpc⁻¹. This represents the first upper limits on the 21 cm power spectrum fluctuations at redshifts 12 ≲ z ≲ 18 but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window.
Published: 2016

179. THE MURCHISON WIDEFIELD ARRAY 21 cm POWER SPECTRUM ANALYSIS METHODOLOGY

Author: Haystack Observatory, Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, de Oliveira Costa, Angelica, Ewall-Wice, Aaron Michael, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Morgan, Edward H, Neben, Abraham Richard, Tegmark, Max Erik, Williams, Christopher Leigh, Jacobs, Daniel C., Hazelton, B. J., Trott, C. M., Pindor, B., Sullivan, I. S., Pober, J. C., Barry, N., Beardsley, A. P., Bernardi, G., Bowman, Judd D., Briggs, F., Cappallo, R. J., Carroll, P., Emrich, D., Gaensler, B. M., Greenhill, L. J., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kim, H. S., Lenc, E., Line, J., Loeb, A., Lynch, M. J., McKinley, B., Mitchell, D.A., Morales, M. F., Thyagarajan, N., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, S., Prabu, T., Procopio, P., Riding, J., Roshi, A., Shankar, N. Udaya, Sethi, Shiv K., Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Wu, C., Wyithe, J. S. B., Corey, B. E., Kratzenberg, E., Lonsdale, C. J., Rogers, A. E. E., Haystack Observatory, Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, de Oliveira Costa, Angelica, Ewall-Wice, Aaron Michael, Feng, Lu, Goeke, Robert F, Hewitt, Jacqueline N, Morgan, Edward H, Neben, Abraham Richard, Tegmark, Max Erik, Williams, Christopher Leigh, Jacobs, Daniel C., Hazelton, B. J., Trott, C. M., Pindor, B., Sullivan, I. S., Pober, J. C., Barry, N., Beardsley, A. P., Bernardi, G., Bowman, Judd D., Briggs, F., Cappallo, R. J., Carroll, P., Emrich, D., Gaensler, B. M., Greenhill, L. J., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kim, H. S., Lenc, E., Line, J., Loeb, A., Lynch, M. J., McKinley, B., Mitchell, D.A., Morales, M. F., Thyagarajan, N., Oberoi, D., Offringa, A. R., Ord, S. M., Paul, S., Prabu, T., Procopio, P., Riding, J., Roshi, A., Shankar, N. Udaya, Sethi, Shiv K., Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Wu, C., Wyithe, J. S. B., Corey, B. E., Kratzenberg, E., Lonsdale, C. J., and Rogers, A. E. E.
Abstract: We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple independent data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction, and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds., National Science Foundation (U.S.) (award AST-1109257), National Science Foundation (U.S.). Astronomy and Astrophysics Postdoctoral Fellowship (award AST 1109257), Australian Research Council (DECRA Award DEI140100316), National Science Foundation (U.S.) (grant AST-1410484), National Science Foundation (U.S.) (grant AST-0821321), National Science Foundation (U.S.) (grant AST-0457585), National Science Foundation (U.S.) (grant PHYS-0835713), National Science Foundation (U.S.) (grant CAREER-0847753), National Science Foundation (U.S.) (grant AST-0908884), Australian Research Council (LIEF grant LE0775621), Australian Research Council (LIEF grant LE0882938), Smithsonian Astrophysical Observatory, Massachusetts Institute of Technology. School of Science, Raman Research Institute, Australian National University, Victoria University of Wellington, New Zealand. Ministry of Economic Development (grant MED-E1799), IBM Research (Shared University Research Grant)
Published: 2016

180. First season MWA EoR power spectrum results at redshift 7

Author: Beardsley, A., Hazelton, B., Sullivan, I., Carroll, P., Barry, N., Rahimi, M., Pindor, B., Trott, Cathryn, Line, J., Jacobs, D., Morales, M., Pober, J., Bernardi, G., Bowman, J., Busch, M., Briggs, F., Cappallo, R., Corey, B., Oliveira-Costa, A., Dillon, J., Emrich, David, Ewall-Wice, A., Feng, L., Gaensler, B., Goeke, R., Greenhill, L., Hewitt, J., Hurley-Walker, Natasha, Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Lenc, E., Loeb, A., Lonsdale, C., Lynch, Mervyn, McKinley, B., McWhirter, S., Mitchell, D., Morgan, E., Neben, A., Thyagarajan, N., Oberoi, D., Offringa, A., Ord, S., Paul, S., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Tegmark, M., Tingay, Steven, Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, Andrew, Williams, C., Wu, C., Wyithe, J., Beardsley, A., Hazelton, B., Sullivan, I., Carroll, P., Barry, N., Rahimi, M., Pindor, B., Trott, Cathryn, Line, J., Jacobs, D., Morales, M., Pober, J., Bernardi, G., Bowman, J., Busch, M., Briggs, F., Cappallo, R., Corey, B., Oliveira-Costa, A., Dillon, J., Emrich, David, Ewall-Wice, A., Feng, L., Gaensler, B., Goeke, R., Greenhill, L., Hewitt, J., Hurley-Walker, Natasha, Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Lenc, E., Loeb, A., Lonsdale, C., Lynch, Mervyn, McKinley, B., McWhirter, S., Mitchell, D., Morgan, E., Neben, A., Thyagarajan, N., Oberoi, D., Offringa, A., Ord, S., Paul, S., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Tegmark, M., Tingay, Steven, Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, Andrew, Williams, C., Wu, C., and Wyithe, J.
Abstract: The Murchison Widefield Array (MWA) has collected hundreds of hours of Epoch of Reionization (EoR) data and now faces the challenge of overcoming foreground and systematic contamination to reduce the data to a cosmological measurement. We introduce several novel analysis techniques, such as cable reflection calibration, hyper-resolution gridding kernels, diffuse foreground model subtraction, and quality control methods. Each change to the analysis pipeline is tested against a two-dimensional power spectrum figure of merit to demonstrate improvement. We incorporate the new techniques into a deep integration of 32 hours of MWA data. This data set is used to place a systematic-limited upper limit on the cosmological power spectrum of ∆2 ≤ 2.7×104 mK2 at k =0.27 h Mpc-1 and z = 7.1, consistent with other published limits, and a modest improvement (factor of 1.4) over previous MWA results. From this deep analysis, we have identified a list of improvements to be made to our EoR data analysis strategies. These improvements will be implemented in the future and detailed in upcoming publications.
Published: 2016

181. The murchison widefield array 21 cm power spectrum analysis methodology

Author: Jacobs, D., Hazelton, B., Trott, C., Dillon, J., Pindor, B., Sullivan, I., Pober, J., Barry, N., Beardsley, A., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Carroll, P., Corey, B., Oliveira-Costa, A., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B., Goeke, R., Greenhill, L., Hewitt, J., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Lenc, E., Line, J., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Neben, A., Thyagarajan, N., Oberoi, D., Offringa, A., Ord, S., Paul, S., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Tegmark, M., Tingay, Steven, Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, A., Williams, C., Wu, C., Wyithe, J., Jacobs, D., Hazelton, B., Trott, C., Dillon, J., Pindor, B., Sullivan, I., Pober, J., Barry, N., Beardsley, A., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Carroll, P., Corey, B., Oliveira-Costa, A., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B., Goeke, R., Greenhill, L., Hewitt, J., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Lenc, E., Line, J., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Neben, A., Thyagarajan, N., Oberoi, D., Offringa, A., Ord, S., Paul, S., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Tegmark, M., Tingay, Steven, Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, A., Williams, C., Wu, C., and Wyithe, J.
Abstract: We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple independent data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction, and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds.
Published: 2016

182. The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses

Author: Franzen, Thomas, Jackson, Carole, Offringa, A., Ekers, Ronald, Wayth, Randall, Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Gaensler, B., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Kaplan, D., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Morgan, J., Oberoi, D., Ord, S., Prabu, T., Seymour, Nick, Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Trott, Cathryn, Webster, R., Williams, Andrew, Williams, C., Franzen, Thomas, Jackson, Carole, Offringa, A., Ekers, Ronald, Wayth, Randall, Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Gaensler, B., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Kaplan, D., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Morgan, J., Oberoi, D., Ord, S., Prabu, T., Seymour, Nick, Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Trott, Cathryn, Webster, R., Williams, Andrew, and Williams, C.
Abstract: © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image has a bandwidth of 30.72 MHz, a field-of-view within the half-power contour of the primary beam of 570 deg2, a resolution of 2.3 arcmin and contains 13 458 sources above 5s. The rms noise in the centre of the image is 4-5 mJy beam-1. The MWA counts are in excellent agreement with counts from other instruments and are the most precise ever derived in the flux density range 30-200 mJy due to the sky area covered. Using the deepest available source count data, we find that the MWA image is affected by sidelobe confusion noise at the ˜3.5 mJy beam-1 level, due to incompletely peeled and out-of-image sources, and classical confusion becomes apparent at ˜1.7 mJy beam-1. This work highlights that (i) further improvements in ionospheric calibration and deconvolution imaging techniques would be required to probe to the classical confusion limit and (ii) the shape of low-frequency source counts, including any flattening towards lower flux densities, must be determined from deeper ˜150 MHz surveys as it cannot be directly inferred from higher frequency data.
Published: 2016

183. CHIPS: The Cosmological H i Power Spectrum Estimator

Author: Trott, Cathryn, Pindor, B., Procopio, P., Wayth, Randall, Mitchell, D., McKinley, B., Tingay, Steven, Barry, N., Beardsley, A., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Carroll, P., Oliveira-Costa, A., Dillon, J., Ewall-Wice, A., Feng, L., Greenhill, L., Hazelton, B., Hewitt, J., Hurley-Walker, Natasha, Johnston-Hollitt, M., Jacobs, D., Kaplan, D., Kim, H., Lenc, E., Line, J., Loeb, A., Lonsdale, C., Morales, M., Morgan, E., Neben, A., Thyagarajan, N., Oberoi, D., Offringa, A., Ord, Stephen, Paul, S., Pober, J., Prabu, T., Riding, J., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Sullivan, I., Tegmark, M., Webster, R., Williams, Andrew, Williams, C., Wu, C., Wyithe, J., Trott, Cathryn, Pindor, B., Procopio, P., Wayth, Randall, Mitchell, D., McKinley, B., Tingay, Steven, Barry, N., Beardsley, A., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Carroll, P., Oliveira-Costa, A., Dillon, J., Ewall-Wice, A., Feng, L., Greenhill, L., Hazelton, B., Hewitt, J., Hurley-Walker, Natasha, Johnston-Hollitt, M., Jacobs, D., Kaplan, D., Kim, H., Lenc, E., Line, J., Loeb, A., Lonsdale, C., Morales, M., Morgan, E., Neben, A., Thyagarajan, N., Oberoi, D., Offringa, A., Ord, Stephen, Paul, S., Pober, J., Prabu, T., Riding, J., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Sullivan, I., Tegmark, M., Webster, R., Williams, Andrew, Williams, C., Wu, C., and Wyithe, J.
Abstract: © 2016. The American Astronomical Society. All rights reserved. Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization (EoR) and estimation of its basic physical parameters are principal scientific aims of many current low-frequency radio telescopes. Here we describe the Cosmological H i Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array, to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximizing the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation ("foreground suppression"). We describe the motivation for the algorithm, implementation, application to real and simulated data, and early outputs. Upon application to a set of 3 hr of data, we set a 2s upper limit on the EoR dimensionless power at Mpc-1 of mK2 in the redshift range z = [6.2-6.6], consistent with previous estimates.
Published: 2016

184. The importance of wide-field foreground removal for 21 cm cosmology: a demonstration with early MWA epoch of reionization observations

Author: Pober, J., Hazelton, B., Beardsley, A., Barry, N., Martinot, Z., Sullivan, I., Morales, M., Bell, M., Bernardi, G., Bhat, N., Bowman, J., Briggs, F., Cappall, R., Carroll, P., Corey, B., de Oliveira-Costar, A., Deshpande, A., Dillon, J., Emrich, D., Ewall-Wice, A., Feng, L., Goeke, R., Greenhill, L., Hewitt, J., Hindson, L., Hurley-Walker, N., Jacobs, D., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kittiwisit, P., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Line, J., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morgan, E., Neben, A., Oberoi, D., Offringa, A., Ord, S., Paul, S., Pindor, B., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Sethi, S., Shankar, N., Srivani, K., Subrahmanyan, R., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, C., Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, A., Williams, C., Wyithe, J., Pober, J., Hazelton, B., Beardsley, A., Barry, N., Martinot, Z., Sullivan, I., Morales, M., Bell, M., Bernardi, G., Bhat, N., Bowman, J., Briggs, F., Cappall, R., Carroll, P., Corey, B., de Oliveira-Costar, A., Deshpande, A., Dillon, J., Emrich, D., Ewall-Wice, A., Feng, L., Goeke, R., Greenhill, L., Hewitt, J., Hindson, L., Hurley-Walker, N., Jacobs, D., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kittiwisit, P., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Line, J., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morgan, E., Neben, A., Oberoi, D., Offringa, A., Ord, S., Paul, S., Pindor, B., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Sethi, S., Shankar, N., Srivani, K., Subrahmanyan, R., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, C., Waterson, M., Wayth, Randall, Webster, R., Whitney, A., Williams, A., Williams, C., and Wyithe, J.
Abstract: In this paper we present observations, simulations, and analysis demonstrating the direct connection between the location of foreground emission on the sky and its location in cosmological power spectra from interferometric redshifted 21 cm experiments. We begin with a heuristic formalism for understanding the mapping of sky coordinates into the cylindrically averaged power spectra measurements used by 21 cm experiments, with a focus on the effects of the instrument beam response and the associated sidelobes. We then demonstrate this mapping by analyzing power spectra with both simulated and observed data from the Murchison Widefield Array. We find that removing a foreground model which includes sources in both the main field-of-view and the first sidelobes reduces the contamination in high k_parallel modes by several percent relative to a model which only includes sources in the main field-of-view, with the completeness of the foreground model setting the principal limitation on the amount of power removed. While small, a percent-level amount of foreground power is in itself more than enough to prevent recovery of any EoR signal from these modes. This result demonstrates that foreground subtraction for redshifted 21 cm experiments is truly a wide-field problem, and algorithms and simulations must extend beyond the main instrument field-of-view to potentially recover the full 21 cm power spectrum.
Published: 2016

185. Parametrizing Epoch of Reionization foregrounds: A deep survey of low-frequency point-source spectra with the Murchison Widefield Array

Author: Offringa, A., Trott, C., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A., Bowman, J., Briggs, F., Carroll, P., Dillon, J., Ewall-Wice, A., Feng, L., Gaensler, B., Greenhill, L., Hazelton, B., Hewitt, J., Jacobs, D., Kim, H., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D., Morales, M., Neben, A., Paul, S., Pindor, B., Pober, J., Procopio, P., Procopio, J., Sethi, S., Shankar, N., Subrahmanyan, R., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Wayth, Randall, Webster, R., Wyithe, J., Offringa, A., Trott, C., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A., Bowman, J., Briggs, F., Carroll, P., Dillon, J., Ewall-Wice, A., Feng, L., Gaensler, B., Greenhill, L., Hazelton, B., Hewitt, J., Jacobs, D., Kim, H., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D., Morales, M., Neben, A., Paul, S., Pindor, B., Pober, J., Procopio, P., Procopio, J., Sethi, S., Shankar, N., Subrahmanyan, R., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Wayth, Randall, Webster, R., and Wyithe, J.
Abstract: © 2016 The Authors. Experiments that pursue detection of signals from the Epoch of Reionization (EoR) are relying on spectral smoothness of source spectra at low frequencies. This article empirically explores the effect of foreground spectra on EoR experiments by measuring high-resolution full-polarization spectra for the 586 brightest unresolved sources in one of the Murchison Widefield Array (MWA) EoR fields using 45 h of observation. A novel peeling scheme is used to subtract 2500 sources from the visibilities with ionospheric and beam corrections, resulting in the deepest, confusion-limited MWA image so far. The resulting spectra are found to be affected by instrumental effects, which limit the constraints that can be set on source-intrinsic spectral structure. The sensitivity and power-spectrum of the spectra are analysed, and it is found that the spectra of residuals are dominated by point spread function sidelobes from nearby undeconvolved sources. We release a catalogue describing the spectral parameters for each measured source.
Published: 2016

186. Beam-forming errors in Murchison Widefield array phased array antennas and their effects on epoch of reionization science

Author: Neben, A., Hewitt, J., Bradley, R., Dillon, J., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Corey, B., Deshpande, A., Goeke, R., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Kaplan, D., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Webster, R., Williams, A., Williams, C., Neben, A., Hewitt, J., Bradley, R., Dillon, J., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Corey, B., Deshpande, A., Goeke, R., Greenhill, L., Hazelton, B., Johnston-Hollitt, M., Kaplan, D., Lonsdale, C., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Shankar, N., Srivani, K., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Webster, R., Williams, A., and Williams, C.
Abstract: Accurate antenna beam models are critical for radio observations aiming to isolate the redshifted 21 cm spectral line emission from the Dark Ages and the Epoch of Reionization (EOR) and unlock the scientific potential of 21 cm cosmology. Past work has focused on characterizing mean antenna beam models using either satellite signals or astronomical sources as calibrators, but antenna-to-antenna variation due to imperfect instrumentation has remained unexplored. We characterize this variation for the Murchison Widefield Array (MWA) through laboratory measurements and simulations, finding typical deviations of the order of ±10%-20% near the edges of the main lobe and in the sidelobes. We consider the ramifications of these results for image- and power spectrum-based science. In particular, we simulate visibilities measured by a 100 m baseline and find that using an otherwise perfect foreground model, unmodeled beam-forming errors severely limit foreground subtraction accuracy within the region of Fourier space contaminated by foreground emission (the "wedge"). This region likely contains much of the cosmological signal, and accessing it will require measurement of per-antenna beam patterns. However, unmodeled beam-forming errors do not contaminate the Fourier space region expected to be free of foreground contamination (the "EOR window"), showing that foreground avoidance remains a viable strategy.
Published: 2016

187. A Large-Scale, Low-Frequency Murchison Widefield Array Survey of Galactic H ii Regions between 260° </<340°

Author: Hindson, L., Johnston-Hollitt, M., Hurley-Walker, Natasha, Callingham, J., Su, H., Morgan, J., Bell, M., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Dwarakanath, K., For, B., Gaensler, B., Greenhill, L., Hancock, P., Hazelton, B., Kapinska, A., Kaplan, D., Lenc, E., Lonsdale, C., Mckinley, B., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Offringa, A., Ord, S., Procopio, P., Prabu, T., Shankar, N., Srivani, K., Staveley-Smith, L., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Webster, R., Williams, A., Williams, C., Wu, C., Zheng, Q., Hindson, L., Johnston-Hollitt, M., Hurley-Walker, Natasha, Callingham, J., Su, H., Morgan, J., Bell, M., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Deshpande, A., Dwarakanath, K., For, B., Gaensler, B., Greenhill, L., Hancock, P., Hazelton, B., Kapinska, A., Kaplan, D., Lenc, E., Lonsdale, C., Mckinley, B., McWhirter, S., Mitchell, D., Morales, M., Morgan, E., Oberoi, D., Offringa, A., Ord, S., Procopio, P., Prabu, T., Shankar, N., Srivani, K., Staveley-Smith, L., Subrahmanyan, R., Tingay, Steven, Wayth, Randall, Webster, R., Williams, A., Williams, C., Wu, C., and Zheng, Q.
Abstract: We have compiled a catalogue of H ii regions detected with the Murchison Widefield Array between 72 and 231 MHz. The multiple frequency bands provided by the Murchison Widefield Array allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in H ii regions. We detect 306 H ii regions between 260°< / < 340° and report on the positions, sizes, peak, integrated flux density, and spectral indices of these H ii regions. By identifying the point at which H ii regions transition from the optically thin to thick regime, we derive the physical properties including the electron density, ionised gas mass, and ionising photon flux, towards 61 H ii regions. This catalogue of H ii regions represents the most extensive and uniform low frequency survey of H ii regions in the Galaxy to date.
Published: 2016

188. Delay spectrum with phase-tracking arrays: extracting the H i power spectrum from the epoch of reionization

Author: Paul, S., Sethi, S., Morales, M., Dwarkanath, K., Shankar, N., Subrahmanyan, R., Barry, N., Beardsley, A., Bowman, J., Briggs, F., Carroll, P., De Oliveira-Costa, A., Dillon, J., Ewall-Wice, A., Feng, L., Greenhill, L., Gaensler, B., Hazelton, B., Hewitt, J., Hurley-Walker, Natasha, Jacobs, D., Kim, H., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., McKinley, B., Mitchell, D., Neben, A., Offringa, A., Pindor, B., Pober, J., Procopio, P., Riding, J., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, Cathryn, Wayth, Randall, Webster, R., Wyithe, J., Cappallo, R., Johnston-Hollitt, M., Kaplan, D., Lonsdale, C., McWhirter, S., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Srivani, K., Williams, A., Williams, C., Paul, S., Sethi, S., Morales, M., Dwarkanath, K., Shankar, N., Subrahmanyan, R., Barry, N., Beardsley, A., Bowman, J., Briggs, F., Carroll, P., De Oliveira-Costa, A., Dillon, J., Ewall-Wice, A., Feng, L., Greenhill, L., Gaensler, B., Hazelton, B., Hewitt, J., Hurley-Walker, Natasha, Jacobs, D., Kim, H., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., McKinley, B., Mitchell, D., Neben, A., Offringa, A., Pindor, B., Pober, J., Procopio, P., Riding, J., Sullivan, I., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, Cathryn, Wayth, Randall, Webster, R., Wyithe, J., Cappallo, R., Johnston-Hollitt, M., Kaplan, D., Lonsdale, C., McWhirter, S., Morgan, E., Oberoi, D., Ord, S., Prabu, T., Srivani, K., Williams, A., and Williams, C.
Abstract: The detection of redshifted 21 cm emission from the epoch of reionization (EoR) is a challenging task owing to strong foregrounds that dominate the signal. In this paper, we propose a general method, based on the delay spectrum approach, to extract H i power spectra that are applicable to tracking observations using an imaging radio interferometer (»Delay Spectrum with Imaging Arrays»). Our method is based on modeling the H i signal taking into account the impact of wide field effects such as the w-term, which are then used as appropriate weights in cross-correlating the measured visibilities. Our method is applicable to any radio interferometer that tracks a phase center and could be utilized for arrays such as the Murchison Widefield Array (MWA), Low Frequency Array (LOFAR), Giant Meterwave Radio Telescope (GMRT), Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), and HERA. In the literature the delay spectrum approach has been implemented for near-redundant baselines using drift scan observations. In this paper we explore the scheme for non-redundant tracking arrays. This is the first application of delay spectrum methodology to such data to extract the H i signal. We analyze 3 hr of MWA tracking data on the EoR1 field. We present both two-dimensional () and one-dimensional (k) power spectra from the analysis. Our results are in agreement with the findings of other pipelines developed to analyze the MWA EoR data.
Published: 2016

189. A high reliability survey of discrete Epoch of Reionization foreground sources in the MWA EoR0 field

Author: Carroll, P., Line, J., Morales, M., Barry, N., Beardsley, A., Hazelton, B., Jacobs, D., Pober, J., Sullivan, I., Webster, R., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Corey, B., de Oliveira-Costa, A., Dillon, J., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B., Goeke, R., Greenhill, L., Hewitt, N., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Lenc, E., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morgan, E., Neben, A., Oberoi, D., Offringa, A., Ord, S., Paul, S., Pindor, B., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, C., Waterson, M., Wayth, Randall, Whitney, A., Williams, A., Williams, C., Wu, C., Wyithe, J., Carroll, P., Line, J., Morales, M., Barry, N., Beardsley, A., Hazelton, B., Jacobs, D., Pober, J., Sullivan, I., Webster, R., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R., Corey, B., de Oliveira-Costa, A., Dillon, J., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B., Goeke, R., Greenhill, L., Hewitt, N., Hurley-Walker, N., Johnston-Hollitt, M., Kaplan, D., Kasper, J., Kim, H., Kratzenberg, E., Lenc, E., Loeb, A., Lonsdale, C., Lynch, M., McKinley, B., McWhirter, S., Mitchell, D., Morgan, E., Neben, A., Oberoi, D., Offringa, A., Ord, S., Paul, S., Pindor, B., Prabu, T., Procopio, P., Riding, J., Rogers, A., Roshi, A., Shankar, N., Sethi, S., Srivani, K., Subrahmanyan, R., Tegmark, M., Thyagarajan, N., Tingay, Steven, Trott, C., Waterson, M., Wayth, Randall, Whitney, A., Williams, A., Williams, C., Wu, C., and Wyithe, J.
Abstract: Detection of the epoch of reionization HI signal requires a precise understanding of the intervening galaxies and AGN, both for instrumental calibration and foreground removal. We present a catalogue of 7394 extragalactic sources at 182 MHz detected in the RA = 0 field of the Murchison Widefield Array Epoch of Reionization observation programme. Motivated by unprecedented requirements for precision and reliability we develop new methods for source finding and selection. We apply machine learning methods to self-consistently classify the relative reliability of 9490 source candidates. A subset of 7466 are selected based on reliability class and signal-to-noise ratio criteria. These are statistically cross-matched to four other radio surveys using both position and flux density information. We find 7369 sources to have confident matches, including 90 partially resolved sources that split into a total of 192 sub-components. An additional 25 unmatched sources are included as new radio detections. The catalogue sources have a median spectral index of -0.85. Spectral flattening is seen towards lower frequencies with a median of -0.71 predicted at 182 MHz. The astrometric error is 7 arcsec compared to a 2.3 arcmin beam FWHM. The resulting catalogue covers ~1400 deg2 and is complete to approximately 80 mJy within half beam power. This provides the most reliable discrete source sky model available to date in the MWA EoR0 field for precision foreground subtraction.
Published: 2016

190. Foreword

Author: Briggs, F
Published: 1997
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191. Magnitude of cognitive dysfunction in adults with type 2 diabetes: a meta-analysis of six cognitive domains and the most frequently reported neuropsychological tests within domains

Author: Palta, P., Schneider, A., Biessels, G.J., Touradji, P., Hill-Briggs, F., Theoretical Biology and Bioinformatics, Sub Theoretical Biology & Bioinformatics, Theoretical Biology and Bioinformatics, and Sub Theoretical Biology & Bioinformatics
Subjects: medicine.medical_specialty, Metabolic disorders, Type 2 diabetes, Neuropsychological Tests, Audiology, Assessment, behavioral disciplines and activities, Article, Chronic disease, Visual memory, Diabetes mellitus, medicine, Humans, Psychiatry, General Neuroscience, Neuropsychology, Cognition, medicine.disease, Cardiovascular disease, Psychiatry and Mental health, Clinical Psychology, Diabetes Mellitus, Type 2, Central nervous system, International (English), Meta-analysis, Neurology (clinical), Verbal memory, Cognition Disorders, Psychology, Endocrine, Stroop effect
Abstract: The objectives were to conduct a meta-analysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards to determine effect sizes (Cohen's d) for cognitive dysfunction in adults with type 2 diabetes, relative to nondiabetic controls, and to obtain effect sizes for the most commonly reported neuropsychological tests within domains. Twenty-four studies, totaling 26,137 patients (n = 3351 with diabetes), met study inclusion criteria. Small to moderate effect sizes were obtained for five of six domains: motor function (3 studies, n = 2374; d = −0.36), executive function (12 studies, n = 1784; d = −0.33), processing speed (16 studies, n = 3076; d = −0.33), verbal memory (15 studies, n = 4,608; d = −0.28), and visual memory (6 studies, n = 1754; d = −0.26). Effect size was smallest for attention/concentration (14 studies, n = 23,143; d = −0.19). The following tests demonstrated the most notable performance decrements in diabetes samples: Grooved Pegboard (dominant hand) (d = −0.60), Rey Auditory Verbal Learning Test (immediate) (d = −0.40), Trails B (d = −0.39), Rey-Osterreith Complex Figure (delayed) (d = −0.38), Trails A (d = −0.34), and Stroop Part I (d = −0.28). This study provides effect sizes to power future epidemiological and clinical diabetes research studies examining cognitive function and to help inform the selection of neuropsychological tests. (JINS, 2014, 20, 1–14)
Published: 2014

192. LOW-FREQUENCY OBSERVATIONS OF LINEARLY POLARIZED STRUCTURES IN THE INTERSTELLAR MEDIUM NEAR THE SOUTH GALACTIC POLE

Author: Lenc, E., primary, Gaensler, B. M., additional, Sun, X. H., additional, Sadler, E. M., additional, Willis, A. G., additional, Barry, N., additional, Beardsley, A. P., additional, Bell, M. E., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Callingham, J. R., additional, Cappallo, R. J., additional, Carroll, P., additional, Corey, B. E., additional, Oliveira-Costa, A. de, additional, Deshpande, A. A., additional, Dillon, J. S., additional, Dwarkanath, K. S., additional, Emrich, D., additional, Ewall-Wice, A., additional, Feng, L., additional, For, B.-Q., additional, Goeke, R., additional, Greenhill, L. J., additional, Hancock, P., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Hindson, L., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, Jacobs, D. C., additional, Kapińska, A. D., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kim, H.-S., additional, Kratzenberg, E., additional, Line, J., additional, Loeb, A., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Morgan, J., additional, Murphy, T., additional, Neben, A. R., additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S. M., additional, Paul, S., additional, Pindor, B., additional, Pober, J. C., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Sethi, S. K., additional, Srivani, K. S., additional, Staveley-Smith, L., additional, Subrahmanyan, R., additional, Sullivan, I. S., additional, Tegmark, M., additional, Thyagarajan, Nithyanandan, additional, Tingay, S. J., additional, Trott, C., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, Wyithe, J. S. B., additional, and Zheng, Q., additional
Published: 2016
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193. GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey – I. A low-frequency extragalactic catalogue

Author: Hurley-Walker, N, primary, Callingham, J R, additional, Hancock, P J, additional, Franzen, T M O, additional, Hindson, L, additional, Kapińska, A D, additional, Morgan, J, additional, Offringa, A R, additional, Wayth, R B, additional, Wu, C, additional, Zheng, Q, additional, Murphy, T, additional, Bell, M E, additional, Dwarakanath, K S, additional, For, B, additional, Gaensler, B M, additional, Johnston-Hollitt, M, additional, Lenc, E, additional, Procopio, P, additional, Staveley-Smith, L, additional, Ekers, R, additional, Bowman, J D, additional, Briggs, F, additional, Cappallo, R J, additional, Deshpande, A A, additional, Greenhill, L, additional, Hazelton, B J, additional, Kaplan, D L, additional, Lonsdale, C J, additional, McWhirter, S R, additional, Mitchell, D A, additional, Morales, M F, additional, Morgan, E, additional, Oberoi, D, additional, Ord, S M, additional, Prabu, T, additional, Shankar, N Udaya, additional, Srivani, K S, additional, Subrahmanyan, R, additional, Tingay, S J, additional, Webster, R L, additional, Williams, A, additional, and Williams, C L, additional
Published: 2016
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194. The radio spectral energy distribution of infrared-faint radio sources

Author: Herzog, A., primary, Norris, R. P., additional, Middelberg, E., additional, Seymour, N., additional, Spitler, L. R., additional, Emonts, B. H. C., additional, Franzen, T. M. O., additional, Hunstead, R., additional, Intema, H. T., additional, Marvil, J., additional, Parker, Q. A., additional, Sirothia, S. K., additional, Hurley-Walker, N., additional, Bell, M., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Callingham, J. R., additional, Deshpande, A. A., additional, Dwarakanath, K. S., additional, For, B.-Q., additional, Greenhill, L. J., additional, Hancock, P., additional, Hazelton, B. J., additional, Hindson, L., additional, Johnston-Hollitt, M., additional, Kapińska, A. D., additional, Kaplan, D. L., additional, Lenc, E., additional, Lonsdale, C. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Morgan, J., additional, Oberoi, D., additional, Offringa, A., additional, Ord, S. M., additional, Prabu, T., additional, Procopio, P., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Staveley-Smith, L., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Wayth, R. B., additional, Webster, R. L., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, Zheng, Q., additional, Bannister, K. W., additional, Chippendale, A. P., additional, Harvey-Smith, L., additional, Heywood, I., additional, Indermuehle, B., additional, Popping, A., additional, Sault, R. J., additional, and Whiting, M. T., additional
Published: 2016
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195. THE MURCHISON WIDEFIELD ARRAY 21 cm POWER SPECTRUM ANALYSIS METHODOLOGY

Author: Jacobs, Daniel C., primary, Hazelton, B. J., additional, Trott, C. M., additional, Dillon, Joshua S., additional, Pindor, B., additional, Sullivan, I. S., additional, Pober, J. C., additional, Barry, N., additional, Beardsley, A. P., additional, Bernardi, G., additional, Bowman, Judd D., additional, Briggs, F., additional, Cappallo, R. J., additional, Carroll, P., additional, Corey, B. E., additional, Oliveira-Costa, A. de, additional, Emrich, D., additional, Ewall-Wice, A., additional, Feng, L., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hewitt, J. N., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kim, HS, additional, Kratzenberg, E., additional, Lenc, E., additional, Line, J., additional, Loeb, A., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Neben, A. R., additional, Thyagarajan, N., additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S. M., additional, Paul, S., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Sethi, Shiv K., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tegmark, M., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, and Wyithe, J. S. B., additional
Published: 2016
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196. A high reliability survey of discrete Epoch of Reionization foreground sources in the MWA EoR0 field

Author: Carroll, P. A., primary, Line, J., additional, Morales, M. F., additional, Barry, N., additional, Beardsley, A. P., additional, Hazelton, B. J., additional, Jacobs, D. C., additional, Pober, J. C., additional, Sullivan, I. S., additional, Webster, R. L., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, de Oliveira-Costa, A., additional, Dillon, J. S., additional, Emrich, D., additional, Ewall-Wice, A., additional, Feng, L., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hewitt, J. N., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kim, HS., additional, Kratzenberg, E., additional, Lenc, E., additional, Loeb, A., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morgan, E., additional, Neben, A. R., additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S. M., additional, Paul, S., additional, Pindor, B., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Sethi, S. K., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tegmark, M., additional, Thyagarajan, Nithyanandan, additional, Tingay, S. J., additional, Trott, C. M., additional, Waterson, M., additional, Wayth, R. B., additional, Whitney, A. R., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, and Wyithe, J. S. B., additional
Published: 2016
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197. Time-domain and spectral properties of pulsars at 154 MHz

Author: Bell, M. E., primary, Murphy, Tara, additional, Johnston, S., additional, Kaplan, D. L., additional, Croft, S., additional, Hancock, P., additional, Callingham, J. R., additional, Zic, A., additional, Dobie, D., additional, Swiggum, J. K., additional, Rowlinson, A., additional, Hurley-Walker, N., additional, Offringa, A. R., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Wayth, R. B., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2016
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198. First limits on the 21 cm power spectrum during the Epoch of X-ray heating

Author: Ewall-Wice, A., primary, Dillon, Joshua S., additional, Hewitt, J. N., additional, Loeb, A., additional, Mesinger, A., additional, Neben, A. R., additional, Offringa, A. R., additional, Tegmark, M., additional, Barry, N., additional, Beardsley, A. P., additional, Bernardi, G., additional, Bowman, Judd D., additional, Briggs, F., additional, Cappallo, R. J., additional, Carroll, P., additional, Corey, B. E., additional, de Oliveira-Costa, A., additional, Emrich, D., additional, Feng, L., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, Jacobs, Daniel C., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kim, HS, additional, Kratzenberg, E., additional, Lenc, E., additional, Line, J., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Thyagarajan, Nithyanandan, additional, Oberoi, D., additional, Ord, S. M., additional, Paul, S., additional, Pindor, B., additional, Pober, J. C., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Sethi, Shiv K., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Sullivan, I. S., additional, Tingay, S. J., additional, Trott, C. M., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, and Wyithe, J. S. B., additional
Published: 2016
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199. The 154 MHz radio sky observed by the Murchison Widefield Array: noise, confusion, and first source count analyses

Author: Franzen, T. M. O., primary, Jackson, C. A., additional, Offringa, A. R., additional, Ekers, R. D., additional, Wayth, R. B., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Morgan, J., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Seymour, N., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Trott, C. M., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2016
Full Text: View/download PDF

200. High-energy sources at low radio frequency: the Murchison Widefield Array view ofFermiblazars

Author: Giroletti, M., primary, Massaro, F., additional, D’Abrusco, R., additional, Lico, R., additional, Burlon, D., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, Morgan, J., additional, Pavlidou, V., additional, Bell, M., additional, Bernardi, G., additional, Bhat, R., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Ewall-Rice, A., additional, Emrich, D., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hindson, L., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Feng, L., additional, Jacobs, D., additional, Kudryavtseva, N., additional, Lenc, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S. M., additional, Pindor, B., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional
Published: 2016
Full Text: View/download PDF

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