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http://hdl.handle.net/20.500.12386/26320
Titolo: | The 154 MHz radio sky observed by the Murchison Widefield Array: noise, confusion, and first source count analyses | Autori: | Franzen, T. M. O. Jackson, C. A. Offringa, A. R. Ekers, R. D. Wayth, R. B. BERNARDI, GIANNI Bowman, J. D. Briggs, F. Cappallo, R. J. Deshpande, A. A. Gaensler, B. M. Greenhill, L. J. Hazelton, B. J. Johnston-Hollitt, M. Kaplan, D. L. Lonsdale, C. J. McWhirter, S. R. Mitchell, D. A. Morales, M. F. Morgan, E. Morgan, J. Oberoi, D. Ord, S. M. Prabu, T. Seymour, N. Shankar, N. Udaya Srivani, K. S. Subrahmanyan, R. Tingay, S. J. Trott, C. M. Webster, R. L. Williams, A. Williams, C. L. |
Data pubblicazione: | 2016 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 459 | Fascicolo: | 3 | Da pagina:: | 3314 | Abstract: | 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 deg<SUP>2</SUP>, a resolution of 2.3 arcmin and contains 13 458 sources above 5σ. The rms noise in the centre of the image is 4-5 mJy beam<SUP>-1</SUP>. 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<SUP>-1</SUP> level, due to incompletely peeled and out-of-image sources, and classical confusion becomes apparent at ≈1.7 mJy beam<SUP>-1</SUP>. 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. | URI: | http://hdl.handle.net/20.500.12386/26320 | URL: | https://academic.oup.com/mnras/article/459/3/3314/2595218 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stw823 | Bibcode ADS: | 2016MNRAS.459.3314F | Fulltext: | open |
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