However, I have heard nothing about a proposed method for subtracting out the hypothesized non-velocity component, or even a rationale for doing so....
Originally Posted by TomT
As I understand it, late type galaxies, especially ScI's, have a much higher interstellar gas density than early types. This obviously has an effect on galactic rotation rates and thus Tully Fisher estimates. As astro-uk said, it's risky to use TF between different galaxy types. Russell made adjustments to lower this risk. Were his adjustments really adequate? Wouldn't this difference be a simpler explanation than invoking some unknown and unaddressed and unexplained phenomenon?
Everyone is entitled to his own opinion, but not his own facts.