The Cosmic Distance Scale + Galaxy Properties

Freshman Seminar Project

The primary goal of this project is to produce a Hubble diagram and an estimate of the Hubble Constant using diameters of more distant spiral galaxies as compared to the diameters of galaxies whose distances are known from HST measurements of their distances (especially Andromeda, M81, M101 and M33, but others as well).

The secondary goal is to examine some of the properties of galaxies by plotting various interesting properties of galaxies against others. Examples: 1. apparent magnitude versus redshift 2. apparent diameter versus redshift (see above!) 3. absolute size versus absolute luminosity 4. Surface brightness versus absolute luminosity

Input datasets:

  • early.spirals.dat a file containing all the early type spiral galaxies in the first CfA Redshift survey (about 475).
  • dist.dat a file containing good distance measurements (estimates) for nearby galaxies. Some are early type spirals, ignore the rest.
  • You should:

  • 1. look at all these galaxies on the digitized Palomar sky survey --- see utilities directory for how to extract images using 'getimage'
  • 2. measure their apparent diameters -- do this yourself, don't just look them up! (and it might be worth measuring both major and minor axis diameters). Pictures of galaxies can be greated using getimage , a canned routine on CfA computers tat allows you to access the image database of scanned images of the Palomar digital Sky Survey.
  • 3. plot apparent diameter versus redshift (see supermongo or use your own)
  • 4. estimate the absolute diameters for those galaxies that have non-redshift distances

    After that, try plotting up some of the other quantities you see above in this sample.

    Here are the links to the data files:

  • early.spirals.dat
  • dist.dat
  • early spirals tab file