From jhkpci@cis.rit.edu Wed Jan 31 13:07:16 2007 Date: Wed, 31 Jan 2007 10:57:31 -0500 (EST) From: Joel H. Kastner To: "cpg3287@rit.edu" , "krg0775@rit.edu" , "acl7695@rit.edu" , "rmp7773@rit.edu" , "cxw8453@rit.edu" Cc: Joel Kastner Subject: assignment 6 This assignment is (intentionally) more open-ended than the previous assignments. During class time, we can chat about how to proceed. I've placed 3 more images in the 'Chandra' directory accessible from the class website. The images are: V1647OriAll120ks_03_10.fits -- only X-rays in the energy range 0.3-1.0 keV V1647OriAll120ks_10_25.fits -- only X-rays in the energy range 1.0-2.5 keV V1647OriAll120ks_25_80.fits -- only X-rays in the energy range 2.5-8.0 keV These three energy ranges roughly correspond to photon (X-ray) wavelengths of 1.2-4.0 nm ("soft"), 0.4-1.2 nm ("medium"), and 0.1-0.4 nm ("hard"). ** The assignment: use these new images to determine and compare the "X-ray colors" of the sources in the V1647 Ori field. Compare with each other, and with the 2MASS colors for the same objects. ** So, think about how to define a "color" (hint: for the 2MASS images, we used magnitude differences, which are differences of logarithms, which are RATIOS). Then use your definition to measure the X-ray colors of the same sources you've previously identified in the V1647 Ori field. Then find a good way to show the range of "colors" for the objects. Which object is "reddest" (softest) in X-rays? Which is "bluest" (hardest)? Finally, compare these X-ray colors to the 2MASS (near-infrared) colors of the same objects. It will undoubtedly help to visualize the three images both individually and as a merged RGB image. You can use ds9 or aladin for these visualizations. Be sure to include calculations for the error bars (uncertainties) in your measurements of X-ray counts; think about how these uncertainties "propogate" to uncertainties in X-ray "colors". Good luck! -Joel