Wednesday, June 10, 2009

Colorful Couple of Days


Started out making some color-color plots, beginning with B-V vs V-i. When I got that successfully coded, I saw that the several thousand black dots were very hard to interpret.
Plan: a) make it plot different symbols for "stars" and "galaxies" ; and/or b) use randomu to generate a random selection of objects to narrow the sample to plot.
Option a seemed easier, so I started researching through one of the IDL books, and browsing online documentation. Fairly easily I adapted my code to a plot and oplot of the two groups of objects, with different psym numbers, and looked at some cmds and color-color plots. These were unfortunately very hard to read, still, what with the plethora of points. Soon thereafter, Beth also suggested using different colored dots for the two sets, and I spent the rest of the afternoon working out my new code to include loadct and made the stars appear red in my new set of plots.

These new black and red plots were successful in the cmds and B-V vs V-i plots, in both fields, but I have yet to gotten my code worked out for a B-V vs i-z plot.


Beth helped walk us through the code to add in order to get the 'x' plot display device to not let the plots disappear when overlapped by other windows. Hurray!
She also suggested to me, in addition to the randomu reminder, using !p.multi mechanism to display multiple plots side by side. I used this to make a 2x2 display of my B-V vs V-i plots, with the dual color, solid black, just stars, and just galaxies plots.

Looking at these, there is a kind of stream pattern that could be the stars, it's just clouded over by "galaxies", so another thing I want to do is try to isolate those and highlight the pretty stars' path in red. (When Beth sent me Dylan's work on another project from the Spring semester, I looked at some of his color-color diagrams, and though they were in different bands, they had the same kinds of shapes, with this red line and a black cloud of other objects. My goal will be eventually to get plots as nicely set up as some of the ones in his paper.)

After our group meeting, because of a comment by Gail about how close to the "star cutoff" some of my anomalous objects were, I went back to my code and colored some of the dots on my cmd to distinguish the really starry-stars (this time, 0.85-1.0 classification), from the less star-like ones (0.7-0.85). Sadly, this really didn't help shed much light on the issue, as the two groups were still dispersed amongst each other, not indicative of any particular behavior that either possessed uniquely.
Beth then suggested cutting out some of the faintest objects, as the most likely to be misclassified. So, I started out making new plots with magnitude cut-offs of 23, which resulted in very few stars, in comparison. I think tomorrow I will try bumping it back up to 24 or 25 to see where that leads me.

Goal for Friday:
Work out how to isolate the line of stars OR get the B-V vs i-z color-color diagram code to work.

Other things To Do:
-Randomu to narrow sample size
-Think about some ways to use these plots and info to actually separate out the misclassified galaxies (and reconcile the discrepancy between the Besancon model star population prediction and the number I am currently working with)
-Read (for fun!) the Dark Matter Substructure paper forwarded by Beth, which I do find interesting.
-Work on learning how to use the IDL command line outside of the Developement Environment so that I can work on squid instead of eel, because it seems to be slowing down and choking up a bit more and more every day...
-Figure out a better way to try to hang the clock. ;P

1 comment:

  1. re: reconciling the difference in the Besancon predictions and the current GOODS sample of "stars" - well this isn't going to actually happen :) But you will have a *cleaner* sample of stars and we will do our best with it! I'm not sure what to expect when sniffing for stellar structure at such faint magnitudes. Its the next frontier... but as you are already seeing, it will be a tricky business. If you haven't already, it will be worth your while to read all of Dylan's figs and captions carefully. It may give you some ideas.

    Lets meet on Monday to set specific goals for this summer so we don't get away with just having fun playing with the data :) I want to get you an AAS-able result!