An Accurate Flux Density Scale from 50 MHz to 50 GHz

Abstract

The flux-density scale of Perley & Butler is extended downward to ∼50 MHz by utilizing recent observations with the Karl G. Jansky Very Large Array (VLA) of 20 sources between 220 MHz and 48.1 GHz, and legacy VLA observations at 73.8 MHz. The derived spectral flux densities are placed on an absolute scale by utilizing the Baars et al. values for Cygnus A (3C405) for frequencies below 2 GHz, and the Mars-based polynomials for 3C286, 3C295, and 3C196 from Perley & Butler above 2 GHz. Polynomial expressions are presented for all 20 sources, with accuracy limited by the primary standards to 3%–5% over the entire frequency range. Corrections to the scales proposed by Perley & Butler, and by Scaife & Heald are given.

A High Resolution Survey of the Galactic Plane at 408 MHz

“…They give polynomial fits that define the flux density of a number of sources as a function of frequency. It is difficult to compare our calibration with this work because none of the Perley & Butler (2017) sources are within the CGPS area. The flux densities predicted for 3C 147, 3C 295, and 3C 48 at 408 MHz are within 1.3% of the values used for initial calibration of our data, quoted in Section 3, but that is not really relevant to the problem.…”

“…The flux densities predicted for 3C 147, 3C 295, and 3C 48 at 408 MHz are within 1.3% of the values used for initial calibration of our data, quoted in Section 3, but that is not really relevant to the problem. The best that we can do is to compare the Perley & Butler (2017) scale with the Baars et al (1977) scale on which our calibration is based. Perley & Butler (2017) give ratios of their flux densities to values from Baars et al (1977) at low frequencies; averaged over 10 sources, the Perley & Butler (2017) scale is 0.5% lower than the Baars et al (1977) scale at 328 MHz and 1.3% higher at 1488 MHz.…”

“…The best that we can do is to compare the Perley & Butler (2017) scale with the Baars et al (1977) scale on which our calibration is based. Perley & Butler (2017) give ratios of their flux densities to values from Baars et al (1977) at low frequencies; averaged over 10 sources, the Perley & Butler (2017) scale is 0.5% lower than the Baars et al (1977) scale at 328 MHz and 1.3% higher at 1488 MHz. The agreement is well within the error that we have estimated for our flux densities.…”

“…On the basis of our examination of these two sources of error, we estimate the systematic errors in flux density for the survey to be less than 6%. Perley & Butler (2017) have established a new flux-density scale between 50 MHz and 50 GHz based on VLA measurements. They give polynomial fits that define the flux density of a number of sources as a function of frequency.…”

NGC 741—Mergers and AGN Feedback on a Galaxy-group Scale

“…As there are no calibrated flux density scales well suited for frequencies below 240 MHz (Perley & Butler 2017), we expect only a small difference between these scales (≤ 2%). We do not attempt to correct to a single flux scale.…”