Speaker: Wayne Hayes, School of Information and Computer Science, University of California at Irvine
Title: Is the Universe Spinning?
The current "Standard Model" of cosmology assumes, for the sake of simplicity, that at large enough scales the universe as a whole is both homogeneous (looks the same everywhere) and isotropic (has no preferred direction). The latter assumption implies, if correct, that the universe
as a whole contains no net angular momentum. In other words, it is assumed that although individual objects in the universe may spin along various axes, the sum total of all this angular momentum is zero. Although this is a reasonable assumption, it is a crucial one which, if incorrect, would likely cause significant complications to the Standard Model.
One way to test this assumption is to look at spiral galaxies. They are the largest objects in the universe for which angular momentum can be observed relatively easily. If the universe is isotropic, then the sum total of the observed angular momentum of all spiral galaxies should sum to approximately zero, with an allowed deviation from zero consistent with a three dimensional random walk of N steps, where N is the number of observed galaxies. (We do not expect exactly zero because we can not see all the spiral galaxies in the universe.)
The Sloan Digital Sky Survey is a digital image of about 1/4 of the entire sky, and it contains images of about 1 million galaxies. We have recently invented the first algorithm that can automatically "parse" images of spiral galaxies and extract structural information. Among other things, we can extract the winding direction and approximate orientation of each spiral galaxy, allowing us to estimate the angular momentum of each galaxy.
I will describe the ongoing work of the above project, as well as our preliminary results. Among the biggest hurdles we had to surmount was the fact that although the Sloan Survey has extracted which objects in the sky are galaxies, until recently no algorithm existed to separate spiral galaxies from elliptical and irregular galaxies. The first half of this talk will describe how we separate them using our structural image analysis, and the second half of the talk will discuss our preliminary results measuring the total angular momentum of the observed universe.
This is joint work with Darren Davis and Matthew Kelly, both of UC Irvine.