Photoelectric Observations of the Interacting Galaxies VV 117 and VV 123 Related to the Time of Formation of Their Satellites.
New observations, both photoelectric and photographic, of the Vorontsov-Velyaminov interacting galaxies VV 117 and vV 123 are reported. The colors of the elliptical primary galaxies are B - V = 1.03, U - B = 0.53 for VV 117, and B - V = 0.90, U - B = 0.30 for vV 123, which are normal for their types. The absolute magnitudes for the elliptical primaries, corrected for absorption in our own Galaxy, are MB = - 19.9 for VV 117 and MB = - 19.0 for vV 123. Colors of the nuclei of the blue satellite galaxies, measured through a 7-second-of-arc diaphragm and corrected for local reddening, are (B - V)0 = 0.68, (U - B)0 = 0.04 for vV 117 and (B - V)0 = 0.35, (U - B)0 = -0.05 for VV 123. The relation between integrated color and age for galactic clusters in our own Galaxy is displayed in Figure 7. Estimates of ages of galaxies using Figure 7 will always give a lower limit because integrated colors of aggregates of stars where many generations of stars have been formed over the lifetime of the System will generally be bluer than colors of the oldest associated clusters where a single epoch of star formation took place. Data from M33 and the Magellanic Clouds shows that this lower limit may differ by as much as a factor of 5-10 from the true age. The age of the nuclei of the blue satellites of VV 117 and vV 123 is discussed, using the color data. If internal obscuration is absent, then the nuclei of the satellites are probably old. Therefore, with this condition, the hypothesis that the spiral companions are galaxies just condensing from the intergalactic medium in the wake of the elliptical primaries would be untenable.