Tuesday, June 1, 2010


Today was a bit of a disappointment. I spent the morning going through the Catelan paper on Horizontal Branch stars looking for something about specific frequencies, but all I could find were a few metallicity-morphology relations. After looking through some of the references, I decided to just to an abstract search on ADS for "specific frequency of horizontal branch stars" and "specific frequency of RR Lyrae stars." From the latter search I found a promising paper: "RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys," which has some good information on metallicity and classification that helped my understanding. Unfortunately, it contextualizes its results by pointing out the debate and differing results on this subject, so it's not a settled issue. Also, I'm not sure what definition of specific frequency is being used in the paper, as the number they give is 5.6, which is not what I was expecting. So, that bears some investigation.

Also, I made a nice plot of uncertainty in proper motion (in km/s) versus distance(in pc) from some listed LSST uncertainties (in mas/year). This should be a simple unit conversion problem, but for some reason both axes run from large negative numbers to 0 instead of from 0 up. It seems like the problem occurs where I initialize my vector of distances, because the only thing I to to them is multiply by positive factors but they turn out negative. That'll give me something to futz with tonight, at least.

*update, it turns out I was doing scientific notation wrong in IDL, which was confusing it. I'd also forgotten to convert from mas to radians, which explained why the errors I was getting were so high. Now things look somewhat more reasonable.

1 comment:

  1. Lets meet up first thing after pizza party tomorrow discuss your figure. If you still bugs, we'll squash them. If you don't, then we'll discuss the figure and how we might merge it with what we (will soon) know about horizontal branch stars, RGB stars, and/or main sequence turnoff stars.

    While banging your head against chasing down observational papers - start doing geometry to "observe" the sim from a Solar observer. If you aren't already, its worth writing up notes on your horizontal branch (and other stellar types) research plus references... that way you won't have to chase it down later.