Chengalur-Nordgren Galaxy Pair Sample
Chengalur-Nordgren Galaxy Pair Sample
Galaxies in clusters and pairs have long been used as a means of
determining the ratio of dark matter to luminous material in the
Universe.
While galaxy cluster observations
lead to a knowledge of the dark matter content for the cluster
as a whole, no information is found on the dark matter content of
individual galaxies.
Galaxy pairs, isolated or in small groups,
potentially still possess all of their
original dark matter.
Observations of the relative motion of galaxies in pairs
offer the chance to determine their total mass.This is an ongoing project. The researchers involved are:
Jayaram N. Chengalur - NCRA-TIFR, Post Bag 3, Pune Univ Campus Ganeshkhind, Pune 411 007, India. chengalu@gmrt.ernet.in
Tyler E. Nordgren - USNO-NPOI, PO Box 447, Rural Rte 14, Flagstaff, AZ 86001. nordgren@sextans.lowell.edu
E.E. Salpeter - CRSR, 612 Space Sciences Bldg, Cornell University, Ithaca NY 14853.
Yervant Terzian - NAIC, 512 Space Sciences Bldg, Cornell University, Ithaca NY 14853. terzian@astrosun.tn.cornell.edu
By observing an ensemble of pairs (where one assumes that the orientation of the orbit to the observer is randomly distributed), nominal estimates for an average mass for the pairs in the sample can be determined. Conducting HI observations of late-type spiral galaxy pairs insures the high accuracy of HI velocities.
In previous work one had usually assumed (1) an orbital shape (often circular) and then assumed that (2)
the orbital motion of the
galaxies is due solely to their gravitational attraction.
It is the purpose of this work to ascertain the validity of the first
assumption (which critically affects any derived mass)
and to determine what effect, if any, the degree of isolation has on the second.
To test these assumptions it is necessary to
minimize the biases in the selection of a galaxy pair sample.
Selection Criteria
Tables
Data
Papers
Nordgren Publications Page
nordgren@sextans.lowell.edu