The Flux Density Measurements

The flux density estimates used in this redetermination of the 1934-638 spectrum are listed in the second column of Table 1. The fitted value from the revised polynomial is shown in column 3 while the difference between this and the previous fit is shown in column 4 (in the sense new-old). The origin of each measurement is given in column 5 with additional notes below the Table. The formal errors in all measurements above 1GHz are $\sim$1% or less and are not shown. The flux values listed are of three types;

Molonglo

The Molonglo Reference Catalogue (MRC) at 408MHz is on the scale of Wyllie (1969) which Baars et al. (1977) conclude is very close to their own. The MOST flux scale at 843MHz is essentially an interpolation between the Wyllie 408MHz scale and the scale of the Parkes Catalogue. See Hunstead (1991) for further details.

ATCA

The values designated as `ATCA' in column 5 of the Table were all made with the AT Compact Array using the calibrator 3C286 as the reference. As this source has structure at the $\sim2$ arcsec level, the total flux was estimated by using only the shortest interferometer spacings or by extrapolating the flux density to zero spacing (eg McConnell & McKay 1994). Where possible (Nov 93, Jun 94) elevation-dependent effects were minimised by observing both sources at similar elevations.

There is good evidence from Bonn (Ott et al. 1993) and the VLA (Perley 1993, priv. comm.) that, in the frequency range 1$\sim$10GHz, 3C286 has not changed by more than $\sim$1% from the spectrum published by Baars et al. (1977). The ATCA flux densities in the Table have all been calculated using the Ott et al. (1993) spectrum for 3C286, which differs by no more than 1$\sim$2% from either the Baars et al. (1977) spectrum or from the spectrum currently used at the VLA.

Single-Dish

The values whose origin are indicated in the Table as `Tidbinbilla' and/or `Parkes' are single dish measurements against the calibration source Hydra A, but with Virgo A also occasionally used. As both these sources have considerable angular extent it was necessary to estimate correction factors based on models of the source structure. These factors amount to as much as 5% for Hydra A and 10% for Virgo A, but are probably accurate to 2-3%. (It is intended to measure these factors more accurately at Parkes in the near future).

Ott et al. (1993) found that both Hydra A and Virgo A have changed significantly from their Baars et al. (1977) values so in each case the revised spectrum of Ott et al. (1993) has been used. It is clear from the Table that the single dish fluxes agree rather well with the ATCA interferometer fluxes, confirming the flux ratio of 3C286 to Hydra A implied in the results of Ott et al. (1993).

Table F.1: Revised Flux Density Estimates for 1934-638. Single-dish measurements at Parkes and Tidbinbilla made by J. Reynolds (JER), L. Staveley-Smith (LSS) and J. Chapman (JC). ATCA measurements in Nov 93 made by A. Tzioumis, in Jun 94 made by D. McConnell & D.J.McKay and in Jul 94 made by S. White.

Frequency	Flux Density	Fitted	Change	Origin
(MHz)	(Jy)	(Jy)
408	6.24	6.14	-1.9%	MRC (Large et al.), 1981
843	13.65	13.89	-3.5%	MOST (Campbell-Wilson & Hunstead 1994)
1380	14.96	14.95	-7.9%	ATCA (Nov 93)
1413	14.87	14.88	-8.1%	Parkes (LSS)
1612	14.47	14.33	-9.3%	Parkes (JC)
1660	14.06	14.18	-9.5%	Parkes (LSS)
1665	14.21	14.16	-9.5%	Tidbinbilla (JER)
2295	11.95	11.85	-11.4%	Tidbinbilla, Parkes (JER)
2378	11.75	11.55	-11.5%	ATCA (Nov 93)
4800	5.81	5.83	-7.9%	ATCA (Nov 93)
4800	5.76	5.83		ATCA (Jun 94)
4835	5.72	5.78	-7.8%	ATCA (Jul 94)
4850	5.74	5.76	-7.8%	Parkes (JER)
8415	2.99	2.94	+8.5%	ATCA (Jul 94)
8420	2.97	2.93	+8.5%	Tidbinbilla, Parkes (JER)
8640	2.81	2.84	+9.8%	ATCA (Nov 93)
8640	2.81	2.84		ATCA (Jun 94)