The ubVr photometric system

Basic Reference

Sandage A., Visvanathan N. 1978, ApJ 223, 707


Multicolor and multiaperture photometry in a new u,b,V,r system, standard V26 magnitudes, new types, and velocities are listed for 405 E, S0, SB0, S0/a (and a few Sa) galaxies. Corrections for the effects of color and magnitude variations with aperture are derived. Average colors reduced to theta/D(0)=0.5, and standard V26 magnitudes reduced to theta/D(0)=2.5, are also given for each galaxy.

The existence of color gradient across the face of many galaxies is seen in our data. Colors are generally redder toward the nucleus. The gradients show a strong wavelenght dependence, similar to the C-M effect itself. The mean gradients are the same for E and S0 galaxies separately and show no depedence on absolute magnitude in the range -20 < Mv < -24.

Differentiation of the color-aperture effect gives an average variation of delta (u - V)=0.15 mag in the surface color over the interval 0.1 < theta/D(0) < 1.0. This variation can be explained by an outward decrease in mean metal abundance in the disks and halos by a factor of ~2 over the stated diameter interval.

The mean Galactic reddening obtained from the data smaller by a factor of 2 in b-V, V-r, and u-V than values based on galaxy counts, but is consistent with other recent determination from colors of high-latitude stars and globular clusters.

The C-M effects is shown to be the same for field E and S0 galaxies as cluster and group members. Hence the effect may be universal and, further, present data provide no evidence for differences in the stellar content of early-type galaxies that depend on their environment.


Access to the data and references

Asiago Database on Photometric System (ADPS)

Indices and Parameters

V, b-V, V-r, u-V


u1 and u2 are added to form a single u value at 3550 Å


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Last update: 21 May 1996