INTERPRETING NEW DATA ON LARGE-SCALE BULK FLOWS

摘要

We study the implications of a recent estimate of the bulk flow of a sample of galaxies containing Type Ia supernovae (SN Ia's) by Riess, Press, & Kirshner. We find that their results are quite consistent with power spectra from several currently popular models of structure formation, but that the sample is as yet too sparse to put significant constraints on the power spectrum. We compare this new result with that of Lauer & Postman, with which there is apparent disagreement. We find that for the power spectra we consider, the difference in window functions between the two samples used for the measurements results in a low level of expected correlation between the estimated bulk flows. We calculate a χ~2 for the two measurements taken together and find that their lack of agreement tends to disfavor spectra with excessive power on large scales, but not at a level sufficient to rule them out. A sample consisting of other SN Ia's found in the Asiago catalog is used to study how the sensitivity of the method used by Riess, Press, & Kirshner will improve with increasing sample size. We conclude that the Local Group motion should be able to be determined with a sample of ～100 SN Ia light-curve shapes.