Mass-to-light distributions for binary spiral galaxies

Surface photometry has yielded mass-to-light distributions for 26 binary spiral galaxies whose rotation curves have been measured with the WSRT. In 12 cases the photometry limits exceed the maximum neutral hydrogen radius. In 10 galaxies M/L is constant with radius, while in the others it increases steadily. The mean total mass-to-light ratio for the individual galaxies is 8.5+-1.1 in the B passband. The minimum mass-to-light ratio required for the galaxy pairs to be bound is 5.6+-1.6. The significance of these results for massive haloes is discussed. (author)