Significant improvements in cosmic flow studies over the last couple of years include, for example: (1) unbiased recovery of cosmological parameters, such as Ωm and σ8 Ωm0.6, via quasi-nonlinear likelihood analyses of galaxy PVs; (2) modeling of non-linear clustering effects in power spectrum analyses from PVs, and implementing tools, based on PCA, for evaluating goodness of fit; and (3) better modeling of biased galaxy formation, in order to single out biasing in the comparison of PVs with redshift surveys and to generate proper mock catalogs for calibrating PV analysis methods.
Future developments rely heavily on growth of the available data bases and on refinements of existing catalogs. The VELMOD technique has enabled improved recalibrations of the Mark III (Willick et al. 1997) and SFI (Branchini et al. 2001) catalogs using external information from IRAS redshift surveys. We are planning an improved recalibration of Mark III using as backbone the homogeneous all-sky Shellflow sample, and merging all existing catalogs of PVs of field galaxies into a new Mark IV catalog.
A number of on-going and newly envisioned surveys (6dF, NFP, SNfactory, Warpfire) are expected to increase the size of existing data bases by a factor 4 within 2005. New wide-field surveys such as SLOAN, 2MASS, and DENIS will also provide most valuable complementary data to help control distance calibration errors.
A noticeable impact to precision flow studies should come from supernovae searches whose potential to build up very large catalogs of peculiar velocities (at the rate of a few hundred detections per year) and small relative error is unparalleled by no other distance indicator. (With Δ d / d(SNIa) ~ 8%, 1 SNIa is worth ~ 6 TF or FP measurements!) If a significant fraction of the new SNIe can be caught at peak light and monitored to measure a light curve (yielding precise distance estimates), current TF/FP data sets will be superseded in less than 5 years. Other ambitious surveys, such as those listed above, will complement accurate SN distances with very large data bases thus enabling remarkably tight flow solutions in the near future. There are good reasons to plan a new workshop on Cosmic Flows in 2005!
S.C. would like to thank Ted von Hippel, Chris Simpson, and the scientific organizing committee for their invitation, and for putting together a superb meeting which was so rich in content and which provided the rare opportunity to interact closely with leading (and lively!) scientists from all branches of astrophysics. The editors are also thanked for their patience while this manuscript was being written.
We remain tremendously saddened by the departure of our friend and colleague Jeff Willick who did so much for the advancement of cosmic flow studies and who touched our lives very deeply.