1. ASTR 402 Observational Astronomy 11 April 2006 Dr. H. Geller

2. The Dome Has Arrived

5. Regarding Remaining Homework Assignment #3 2006:090:20:49:07 107.5 66.2 -26.7 -4.9 1419.75 0.00781250 1 64 6.2 7.6 12.9 25.3 50.7 86.2 137.6 187.2 270.8 266.8 1. Discover and explain what each of the column numbers represent (date, time, intensity, lat, long, etc.). In the first column, define all of the parameters represented. 2. Describe the differences between the different rows. Be specific. 3. Using the intensities from one frequency (specify which one you are using) develop a surface (colorized contour) map of the intensity versus the location (RA, dec) of the center of the beam. You may use either Excel or some other data visualization package.

6. Regarding Remaining Homework Assignment #4 Run the Virtual Radio Interferometer Java applet from this site http://www.jb.man.ac.uk/vri/ http://www.jb.man.ac.uk/vri/ Using defaults, choose the sources –Point, Offset Point, Narrow Double, Wide Double, Wide Gaussian, Narrow Gaussian, Disc, Crux, Radio Galaxy –For each different source describe the source and the FFT for each of the sources For a defined configuration (you define what you like to choose as your configuration of dishes) –Set the hour-angle range to zero (this is what is known as a "cut"). Accumulate cuts at hour angles of 0, +4 and -4. Look at the uv- coverage for 6 antennas and describe how the resultant image looks for a specified point as compared to the radio galaxy source. –Start with the declination set to zero. Describe what happens on an east-west array. Now try moving antennas off the E-W line and look at the new uv-coverage.

7. Review Chapter 10 Concepts Photon-electron interactions –Rayleigh Scattering –Thomson Scattering –Compton Scattering Photon Absorption in the Cosmic Microwave Background Radiation

8. Review Chapter 10 Concepts Photon-atom interactions –Photon absorption –Absorption lines –Emission nebulae –Pair production

9. Review Chapter 10 Concepts Starlight Extinction –Interstellar Medium (ISM) dust grains –Extinction Coefficient –Extragalactic Sources –Color Excess (aka reddening) –Frequency Dependence Dust-hydrogen association

10. Review Chapter 10 Concepts Cross sections –Target cross section –Mean propagation distance Exponential absorption Mean free path Optical depth Extinction coefficient cross section

11. Review Chapter 10 Concepts Photoelectric absorption in the ISM –Photoelectric Effect –Cosmic Abundances By number By mass fraction Propagation Distances in the ISM –Effective cross sections –Survival distances –Astronomical gas calculations

12. Review Chapter 10 Concepts