Using Tidal Tails to Probe Dark Matter Halos

John Dubinski, J. Christopher Mihos[1,2] and Lars Hernquist[3]

Board of Studies in Astronomy and Astrophysics
University of California, Santa Cruz, CA 95064
dubinski@lick.ucsc.edu, hos@lick.ucsc.edu, lars@lick.ucsc.edu

[1]Hubble Fellow
[2]Current Address: Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218
[3]Alfred P. Sloan Foundation Fellow, Presidential Faculty Fellow

[Postscript Copy]
[Dubinski, J, Mihos, C., Hernquist, L. 1996, ApJ, 462, 576 -- ADS Abstract Service Link]

Abstract:

We use simulations of merging galaxies to explore the sensitivity of the morphology of tidal tails to variations of the halo mass distributions in the parent galaxies. Our goal is to constrain the mass of dark halos in well-known merging pairs. We concentrate on prograde encounters between equal mass galaxies which represent the best cases for creating tidal tails, but also look at systems with different relative orientations, orbital energies and mass ratios. As the mass and extent of the dark halo increase in the model galaxies, the resulting tidal tails become shorter and less massive, even under the most favorable conditions for producing these features. Our simulations imply that the observed merging galaxies with long tidal tails ( kpc) such as NGC 4038/39 (the Antennae) and NGC 7252 probably have halo:disk+bulge mass ratios less than 10:1. These results conflict with the favored values of the dark halo mass of the Milky Way derived from satellite kinematics and the timing argument which give a halo:disk+bulge mass ratio of . However, the lower bound of the estimated dark halo mass in the Milky Way (mass ratio ) is still consistent with the inferred tidal tail galaxy masses. Our results also conflict with the expectations of cosmologies such as CDM which predict much more massive and extended dark halos.

Keywords: galaxies:interactions -- galaxies:structure -- dark matter -- cosmology:dark matter

• Introduction
• Numerical Methods
  • Galaxy Models
  • Orbital Parameters
  • Numerical Techniques
• Fiducial Encounters
• Other Encounters
  • Bound Orbits
  • Unequal Mass Ratios
  • Inclined Disks: The Antennae
  • A More General Case: The Milky Way and Andromeda
• Discussion
• About this document ...