Several clusters of galaxies, including those observed by Baum (1962), are obvious candidates to begin with. One of these is Cl (0024+1654) which is shown by Zwicky (1959). The southernmost (lowest) galaxy of the three galaxies which form a small isosceles triangle at the center of the cluster was observed with an aperture of 7" diameter. The bandpass below 5800 Å was 80 Å, and above 5800 Å it was 160 Å. The whole spectrum was covered at these bandpasses. Measurements were made with the galaxy first in one aperture, then in the second one, and the results averaged. Five completely separate sets of measurements were made; the last one was not used because of deteriorating seeing conditions. The total observing time was 3 hours. All measurements were reduced to absolute fluxes by standard techniques (Oke 1965) and are based on the absolute calibration of Lyr given by Oke and Schild (1970). The results are shown as dots in Figure 1 where AB = -2.5 logf (ergs s-1 cm-2 Hz-1) -48.60 is plotted against log , where is the observed frequency. The center of the visual passband is marked V. The corresponding visual magnitude is V = 19.9. Standard deviations were calculated by comparing the four individual sets of measures and are shown if greater than 0.10 mag. The accuracy of one point relative to another is probably somewhat higher than shown, since colors are more accurate than magnitude measurements. The observations made below 3900 Å have such large errors that they are not plotted.
Figure 1. Absolute spectral energy distribution for a galaxy in Cl (0024+1654). AB = -2.5 logf (ergs s-1 cm-2 Hz-1) -48.60 and is the observed frequency. Standard-deviation bars are shown if they are larger than 0.10 mag. The redshifted energy distribution for the integrated light from nearby giant elliptical galaxies (Schild and Oke 1971) is shown by the solid line. V marks the center of the V-filter band in the UBV system.
The redshift was determined by superposing the absolute spectral energy distribution of the total light from nearby giant elliptical galaxies (Schild and Oke 1971) and that of the cluster galaxy and shifting one with respect to the other until a fit was obtained. The result is z = 0.38 ± 0.01; no other redshift value is feasible. The "standard galaxy" is shown by the solid line. Several spectral features are marked in Figure 1. There is evidence that the emission line 3727 of [O II] is present, but there is no evidence for emission in H or 5007 of [O III].
A second cluster of particular interest is that around 3C 295. It was decided to observe 3C 295 itself, since something was already known about its spectrum (Minkowski 1960). On the other hand, there was the possibility that the galaxy energy distribution might be quite abnormal. Observations were made in the same was as for Cl (0024+1654). The total observing time was 8 hours. Again an aperture of 7" was used. The results are shown in Figure 2; again standard-deviation bars are shown if greater than 0.10 mag. The corresponding visual magnitude is V = 19.9. Fitting the energy distribution of standard giant elliptical galaxies gave z = 0.46 ± 0.01, in excellent agreement with Minkowski's result of z = 0.462. The [O II] line at 3727 is clearly present. H at an observed wavelength of 9600 Å may be present in emission; it is just to the red of strong absorption bands of water vapor. The [O III] lines 5007 may be present since the flux in the band at log = 14.611 is higher than that for the standard galaxy.
Results are shown in Figure 3 for galaxies 8 + 9 in the Hydra cluster (0855+0321). These galaxies are marked on Plate 1 by Humason et al. (1956). In this object the aperture size and bandpasses were the same as in the previous objects. Total observing time was 4 hours. The visual magnitude is V = 17.3. The value of z from the spectrometer data is 0.20 ± 0.01 in agreement with z = 0.2025 given by Humason et al. (1956).