Thursday, June 3, 2010

Paper Outline

I met with Beth earlier today to discuss the outline of my paper. Here it is:

1. Intro
2. Observations and Data Reduction
--star selection
3. Results
-Age, metallicity, distance
-Absolute Magnitude
-Structural Properties (incl surface brightness)
((mass seg))
4. Implications of tidal features
-Assuming circular orbit --> instantaneous tidal radius
-assuming GC M/L (= a few) --> instantaneous tidal radius
-assuming Wolf et al. mass --> tidal radius
-assuming tidal radius = visible size --> M/L
-assuming 10:1 orbit and currently at apocenter --> tidal radius
5. Conclusions
6. Discussion

I've decided to take a break on the completeness stuff to get moving on the paper. Today and tomorrow I'll work on the first two sections. Then I'll get back to the completeness thing so that I can calculate the magnitude uncertainties. From there I'll work on determining the distance using fiducials and isochrones. When I've decided on a distance I'll use it to inform me about Wil1's age and metallicity. Then I'll go back to the structural properties to finalize them given the results of the completeness testing and also to calculate the Wil1 surface brightness. After that we've got to get back to working on the simulated galaxy to fix problems with the morphology of the simulation.

After all that gets done I'll just have the final calculations for section 4 and interpreting all the data for the conclusions and discussion section. No big deal. (If time permits, we'll then check out the possibility of mass segregation, at least in a preliminary sense.)

Completeness woes

I've been working on the artificial star testing this week and having trouble calculating the completeness. Last Thursday I ran Allframe for the first time on the fake frames. Then on Friday I completed the post-Allframe analysis and dug into calculating the completeness but I was getting crazy values that were nowhere near what they should have been.

After digging through on Monday and Tuesday I had fixed a few bugs. But it wasn't until yesterday that I realized a conversion error between pixel values and ra and dec. The coordinates in the reference frame were correct, but all other frames appeared to have some distortion in the placement of artificial stars. In fact, many of the stars were offset by 2", and so that explains why I wasn't finding them within 0.5" of where I thought I had input them.

Unfortunately, even when I increased the match length to 2.5", I still wasn't matching all of the stars as I had expected if that was the only problem. I chose to re-run Allframe using the fix, but I don't think that will completely solve the problem. One of the things I do in the process of matching Allframe is match between all of the frames to make sure i have at least 2 detections of each star. It is possible that I was losing stars in this step because the inserted stars weren't necessarily coincident between frames (though they were meant to be), however it looked to me as though all frames other than the reference were using the same ra and dec values for the artificial stars. So there should have been only a very few stars lost, namely those appearing on only the reference frame. Still, this problem needed to be fixed and it's very possible that additional errors were introduced when the transformation between frames was calculated using DAOmaster.

I've corrected several bugs in my calculation of the completeness including how I was selecting stars. Today, I'll finish analyzing the latest Allframe run and incorporate that to my completeness calculation to see if I'm matching things any better. I also plan to meet with Beth to discuss an outline for the paper. Then I'll jump into writing the intro.