continuity

A major theme in my talks and research for the last few years is that the Universe we see (ie, an instantaneous picture of our past light cone) is a snapshot of a continuous process in which galaxies are evolving by forming stars, merging, accreting, fading, etc. In principle, if our sample is representative, the entire continuous process ought to be reflected, statistically, in our snapshot. At the very least, the snapshot must be consistent with the continuous process. I imagine, in effect, a kind of continuity equation analysis of the data.

In particular, I think a lot of the trivial ideas thrown into the literature about how galaxies might be evolving are strongly in conflict with this continuity consistency requirement. I worked on that a bit more directly today, by working on my small project (mentioned earlier) on what the galaxy central surface-brightness distribution (ie, the distribution of stellar densities at galaxy centers) has to say about what kinds of processes can be taking place in galaxy evolution.