ASTR 328/438 - Groupwork #3

Cosmic Flows

We are going to study the motion of galaiex in the universe. This involves two conceptual steps: finding peculiar velocities for clusters of galaxies, and then, once a sample is cluster peculiar velocities is built up, solving for the motion. So we'll do this in steps.

First, get a feel for finding peculiar velocities by the following exercises:
 OK, now you have some data. Obviously two data points isn't enough.

So here are two more datasets:
 Add your FP-derived cluster peculiar velocity to the SMAC catalog, and your TF-derived cluster peculiar velocity to the Dale catalog. Note: if your cluster already is in the SMAC and/or Dale catalogs, don't add it. But comment on the difference between your value and that in the SMAC/Dale catalogs.

There are two possibilities of things to do with this data. Pick one:
A.  Measure the bulk motion of these sets of distant clusters through the universe. B. Measure the motion of the local group with respect to the distant clusters.
To do this, use the tabulated peculiar velocities with respect to the CMB. You'll need to correct the peculiar velocities of your two clusters to the CMB reference frame, and you can do this easily using the NED velocity calculator (or by doing the spherical trig yourself!). Then compare the motion you solve for to the bulk motion measurements in the literature.
 To do this, convert the peculiar velocities from the CMB reference frame to the LG reference frame (again using the NED velocity calculator). Once you've done that, compare the motion you get to known motion of the LG (i.e., to the Virgo infall and CMB motions), found in the literature.

Either way, for each of the two datasets, solve for the motion (speed and direction) using this handout from Mihalas and Binney to show you the way.

Standard groupwork rules apply: write it up in ApJ format with the usual sections properly formatted, and statement of work distrubution and any code should also be attached...