Thursday, May 28, 2009

Initial Progress

Well, the search for info has given some results. It just took a while to track down the requisite papers.
In response to comments: The GOODS covers an area of 10'x16' in each of it's two fields. I think that comes out to about 0.0000007 % of the total sky area...

The magnitude limits on the bands were given to be:
B,V= 28.1+/- 0.3
i = 27.4 +/- 0.3
z = 26.95 +/- 0.35

Wednesday I made my first official plot! RA vs Dec of all of the objects in the survey. It wasn't so great at first; I was having a little trouble with the coding. After our group meeting, Beth took a look and helped me out. Turns out I didn't tell it not to connect all of the points, so the funny look was a ton of lines crisscrossing the plot. This was corrected, and then it looked like it should! It then took me longer than it should have to successfully save the image. The next observation was just the sheer multitude of data. All of the survey objects were included.

Since I'm going to be looking at stars, the next step is to sift through and set aside all of the galaxy objects. I had hopes that this wouldn't be all too complicated, as there was a conveniently labeled column in the catalog that read star-galaxy classification parameter. No such luck. The column appears to be a measure on a continuous scale from 0 to 1, and I have been unsuccessful in finding any documentation explaining it. I have decided to e-mail the "help" address given on the GOODS website, as I did for information about the mysterious 10 unlabeled columns (to which the response was that they had been used by the survey team to check for photometric consistency and overlapping in their tiles, and could be ignored for my purposes).

Another idea proposed at our group meeting that I am looking into is to use a random number generator to pick a sample population to plot. Lastly, it was proposed that I combine the catalogs of four bands together. Since I had not previously considered this, I didn't know how difficult it would be, if the objects listed were consistent, or in order. Sphere matching could be used to help this, and pick out matching objects between the catalogs.

Upon examination, I found that no such worries were needed, that the objects in each catalog matched one another. In fact, the first 16 columns of data are all positional information (RA, dec, assigned section numbers, x and y coordinates assigned to describe positions on the tiles, etc), and these were unvarying between all four bands- as it should be! So, I don't think as much work will be required to match up rows to combine them, and maybe there is a relatively easy was to grab non-repeated columns from three of the catalogs and add them to the first. --> probably a good project for today.

The whole of Thursday was spent researching and reading through more papers on the GOODS and its data.

Goal for Friday: Make a plan on how to combine catalogs and make some headway doing so. Also waiting to hear back from "Help" about classification parameter interpretation in order to move on that.

1 comment:

  1. Nice - These are good and faint magnitude limits. We'll be able to use these data to get a nice sense of what the population of MW stars looks like a faint magnitudes - even if its a teeny weeny stamp of the sky! This will be valuable to inform future studies of MW stars in deep data taken from the ground. I'm looking forward to this.