A Funny Thing Happened on the Way to Convergence: The Cosmic Velocity Field
Hume Feldman



Modeling the cosmic velocity field, and especially estimating its lowest order moment, the bulk flow, has been a popular pursuit among aficionados in the cosmological community for three decades now. Other than estimating the magnitude and direction of the flow, one of the main difficulties has been defining the scale of flow detected. There is a nearly universal agreement as to the direction of the flow, however, there are some disagreements regarding the magnitude and scale of the flow. We developed and applied the Minimal Variance (MV) formalism to optimize and clearly define the scale of a particular analysis, using the width of the survey window function as a proxy for scale. Comparing the MV ideal window function to any analysis window function gives an unbiased estimate of the survey characteristic depth (or scale) and thus provides a method to directly compare various results. I will discuss the history of the field, as well as its current state, and compare various recent analyses to show that the disagreements are not as significant as they appear.