How can I get data from other wavelengths to compare with infrared data from Spitzer?
Scientists examine images taken at different wavelengths because different elements and compounds absorb and release light at different wavelengths.
In order to interpret the Spitzer data, we often need to include data from other wavelengths. Lots of data are available online. In any case, it's worth knowing how to do this so that you can find it yourself for any region.
Some good places to start are the following; note that these are real, professional astronomy resources, so they may not have a place where they define terms, etc...
- If you want images in other wavelengths, there are many different ways to do it. A very common one is Skyview at Goddard (http://skyview.gsfc.nasa.gov/). Just save the images as FITS format (jpeg or gif is NOT good enough) and load them into your FITS viewer. Skyview can let you get pretty large images. To do accurate photometry, though, you should use Google to find the original archive for the survey you want, and go get the original images from the original survey.
- A good place to look for additional images is WISE, which is an all-sky survey at wavelengths similar to Spitzer. It's not as sensitive as Spitzer, and it's lower spatial resolution, but it is all-sky. As of Spring 2011, 57% of the sky has been released. Access the archive directly here, and see a step-by-step WISE archive tutorial from Berkeley here.
- IRSA has a TON of different archives, for both images and catalogs. You can search IRSA in any of a variety of ways, including the search option on that main front page. You can also search individual archive holdings by clicking on the specific archive holding in the lower left of the page (on the colored sidebar).
- Gator, at IRSA (http://irsa.ipac.caltech.edu/applications/Gator/). Provides access to 2MASS, IRAS, and other stuff (including actually it appears the optical data also ostensibly retrievable from elsewhere). Try using this to get 2MASS and optical photometry.
- The SHA can also help you get catalogs from other wavelengths. You can save these catalogs to disk from the SHA.
WARNING: don't cavalierly ask the SHA to overlay all of the 2MASS sources in a large region. There are a LOT of 2MASS sources even in a small region, and if you make what might seem like a simple request, you might grind your computer to a halt.
- Note that Gator or other similar web search forms may be superior to the SHA for the very advanced user because Gator gives users more flexibility about the columns that are returned by the search.
- Another place to get optical magnitudes is the USNO (http://www.nofs.navy.mil/data/FchPix/). Make sure to retrieve tables, not images. (There are other resources on the web for images, but this is the only place I know of for the photometry).
Questions to think about and things to try with data at other wavelengths
- Pick a wavelength besides Spitzer's and examine images of your favorite region in that wavelength. How are the features in this wavelength different than they are in Spitzer? Why?
- Can you find images of your favorite region in wavelengths similar to Spitzer's? How are those images different from or similar to Spitzer's?
- Bonus question: can you find already-extracted Spitzer data from other star-forming regions (in Gator or elsewhere)?
Come up with your own answers and then discuss data from other wavelengths.