ASTR 402 Observational Astronomy

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ASTR 402Observational Astronomy

• 11 April 2006
• Dr. H. Geller

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The Dome Has Arrived
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Regarding Remaining Homework Assignment 3
2006090204907 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.
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Regarding Remaining Homework Assignment 4

• Run the Virtual Radio Interferometer Java applet
  from this site 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.

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Review Chapter 10 Concepts

• Photon-electron interactions
• Rayleigh Scattering
• Thomson Scattering
• Compton Scattering
• Photon Absorption in the Cosmic Microwave
  Background Radiation

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Review Chapter 10 Concepts

• Photon-atom interactions
• Photon absorption
• Absorption lines
• Emission nebulae
• Pair production

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Review Chapter 10 Concepts

• Starlight Extinction
• Interstellar Medium (ISM) dust grains
• Extinction Coefficient
• Extragalactic Sources
• Color Excess (aka reddening)
• Frequency Dependence
• Dust-hydrogen association

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Review Chapter 10 Concepts

• Cross sections
• Target cross section
• Mean propagation distance
• Exponential absorption
• Mean free path
• Optical depth
• Extinction coefficient cross section

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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

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Review Chapter 10 Concepts
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Review Chapter 10 Concepts
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Review Chapter 10 Concepts