A broadband flux scale for low frequency radio telescopes

TL;DR

This paper develops broadband spectral models for six bright radio sources between 30-300 MHz, providing a calibration reference for low frequency radio telescopes like LOFAR.

Contribution

It introduces parameterized polynomial spectral models for six radio sources, calibrated across a broad frequency range, to aid low frequency radio astronomy.

Findings

Spectral models achieve low percentage error across 30-300 MHz.

Bayesian evidence used to determine optimal polynomial order.

Maximum likelihood parameters provided with error estimates.

Abstract

We present parameterized broadband spectral models valid at frequencies between 30-300 MHz for six bright radio sources selected from the 3C survey, spread in Right Ascension from 0-24 hours. For each source, data from the literature are compiled and tied to a common flux density scale. These data are then used to parameterize an analytic polynomial spectral calibration model. The optimal polynomial order in each case is determined using the ratio of the Bayesian evidence for the candidate models. Maximum likelihood parameter values for each model are presented, with associated errors, and the percentage error in each model as a function of frequency is derived. These spectral models are intended as an initial reference for science from the new generation of low frequency telescopes now coming on line, with particular emphasis on the Low Frequency Array (LOFAR).