DO SPIRALS AND ELLIPTICALS TRACE THE SAME VELOCITY-FIELD

We test the hypothesis that the velocity field derived from Tully-Fish er measurements of spiral galaxies, and the one derived independently from D(n)-sigma measurements of ellipticals and S0s, are noisy version s of the same underlying velocity field. The radial velocity fields ar e derived using tensor Gaussian smoothing of radius 1200 km s-1. They are compared at grid points near which the sampling by both types of g alaxies is adequate. This requirement defines a volume of congruent-to (50 h-1 Mpc)3, containing approximately 10 independent subvolumes, mo stly limited by the available ellipticals. The two fields are compared using a correlation statistic, whose distribution is determined via M onte Carlo simulations. We find that the data is consistent with the h ypothesis, at the 10% level. We demonstrate that the failure to reject the correlation is not just a result of the errors being big by using the same method to rule out complete independence between the fields at the 99.8% level. The zero points of the two distance indicators are matched by maximizing the correlation between the two velocity fields . There is a marginal hint that the ellipticals tend to stream slower than the spirals by congruent-to 8%. The correlation reinforced here i s consistent with the common working hypotheses that (1) the derived l arge-scale velocity field is real, (2) it has a gravitational origin, and (3) the large-scale velocities of spirals and ellipticals are hard ly biased relative to each other. On the other hand, it does not rule out any alternative to gravity where objects of all types obtain simil ar large-scale velocities.