SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS

Patra, Nipanjana and Subrahmanyan, Ravi and Sethi, Shiv and Shankar, Udaya N and Raghunathan, A (2015) SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS. In: ASTROPHYSICAL JOURNAL, 801 (2).

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Abstract

SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration, and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150 MHz all-sky map of Landecker and Wielebinski: subtracting an offset of 21.4 K and scaling by a factor of 1.05 will reduce the overall offset error to 8 K (from 50 K) and scale error to 0.8% (from 5%). The SARAS measurement of the temperature spectral index is in the range -2.3 to -2.45 in the 110-175MHz band and indicates that the region toward the Galactic bulge has a relatively flatter index.

Item Type:	Journal Article
Publication:	ASTROPHYSICAL JOURNAL
Publisher:	IOP PUBLISHING LTD
Additional Information:	Copy right for this article belongs to the IOP PUBLISHING LTD, TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
Keywords:	cosmic background radiation; methods: observational; radio continuum: ISM
Department/Centre:	Division of Physical & Mathematical Sciences > Joint Astronomy Programme
Date Deposited:	24 Apr 2015 05:40
Last Modified:	24 Apr 2015 05:40
URI:	http://eprints.iisc.ac.in/id/eprint/51373

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