Extragalactic Objects

Vir A = M87

This elliptical galaxy forms the centre of the galaxy cluster in Virgo. It emits X-rays from the black hole in its centre, which is also responsible for the ejection of a radio jet. A drift scan on 1.3 GHz from 31 Dec. 2009 reveals a signal of 0.24 dB above the background. A sharp strong electrical interference occurred at UT 0749. The background before and after the passage of M87 is slighly different.
A flux calibration is not available, but one may reasonably assume that the system temperature was about 50 K. With an assumed zenith temperature of 5 K the antenna temperature of the sky background at the elevation of 39º is T_sky = 5 K /sin(39º) = 7.9 K.
With Y = 10^{0.24 dB/10} = 1.057 and T_CMB = 2.7 K one gets the antenna temperature of M87: T_ant(M87) = (Y-1) * (T_sys + T_CMB + T_sky) = 3.45 K Since the antenna has a sensitivity of about 15 mK/Jy, one computes a radio flux of 230 Jy, in very good agreement with the literature (Kellermann et al. 1969).

Cyg A = 3C405

This radio galaxy has an active nucleus powered by a black hole. From this nucleus two narrow jets of gas are ejected, which collide far outside the galaxy with the ambient intergalactic medium and strong produce radio emission. The drift scan at 1.3 GHz from 31 Dec. 2009 gives a signal of 1.4 dB above the background.
With a system temperature of 50 K and a zenith temperature of 5 K, the antenna temperature of the sky background at elevation 66º is T_sky = 5.5 K.
Y = 10^{1.4 dB/10} = 1.38 yields an antenna temperature: T_ant(CygA) = 22 K
and the radio flux of 1470 Jy, somewhat smaller than 1690 Jy (Vinogradova et al. 1971).

The radio map in the 408 MHz continuum (Haslam et al. 1982) depicts CygA as a bright source. At the same declination 41º one finds other continuum sources in the galactic plane, which come later into the field of view during the drift scan.

Quasar 3C273

A quasar is an active nucleus of a distant galaxy, from which only this bright nucleus is observed. The spectrum shows a non-thermal continuum. The drift scan on 1.3 GHz from 2 Sept. 2014 shows a signal of 0.05dB above the background.
The flux calibration yields a system temperature of 48 K and a zenith temperature of 5 K. With the antenna temperature of the sky background at elevation 31º T_sky = 9.7 K and Y = 10^{0.05 dB/10} = 1.012 one obtains the antenna temperature T_ant(3C273) = 0.72 K
and a radio flux of 48 Jy, in very good agreement with the literatur: 45 Jy (Kellermann et al. 1969).

The Width of the Profiles

The measured profiles are very similar. A drift scan of a point source maps the antenna diagram of the main lobe, which can well be represented by a gaussian function. The full widths at half maximum (FWHM) are:

Object	Declination	FWHM	FWHM (corr.)
Vir A	13	1.92	1.87
Cyg A	41	2.42	1.83
3C273	2	1.33	1.33

The widths which are measured by noting the time needed for the source to pass through the main lobe, need to be corrected for the object's declination, in order to compute the true angular width: FWHM * cos(Dec). From solar measurements the width of the antenna beam (HPBW) is known as 1.8..1.9º.

The table shows that the narrowest profile is found with the quasar 3C273. That it appears to be even narrower than the HPBW, indicates that the matching of the very weak profile by a Gaussian may not have been correct. The widths for M87 and Virgo A agree with the antenna's HPBW, as both are point sources for this antenna.