Measuring galaxy potentials using shell kinematics

MR Merrifield*, K Kuijken

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

33 Citations (Scopus)


We show that the kinematics of the shells seen around some elliptical galaxies provide a new, independent means for measuring the gravitational potentials of elliptical galaxies out to large radii. A numerical simulation of a set of shells formed in the merger between an elliptical and a smaller galaxy reveals that the shells have a characteristic observable kinematic structure, with the maximum line-of-sight velocity increasing linearly as one moves inward from a shell edge. A simple analytic calculation shows that this structure provides a direct measure of the gradient of the gravitational potential at the shell radius. In order to extract this information from attainable data, we have also derived a complete distribution of line-of-sight velocities for material within a shell; comparing the observed spectra of a shell to a stellar template convolved with this distribution will enable us to measure the gradient of the potential at this radius. Repeating the analysis for a whole series of nested shells in a galaxy allows the complete form of the gravitational potential as a function of radius to be mapped out. The requisite observations lie within reach of the up-coming generation of large telescopes.

Original languageEnglish
Pages (from-to)1292-1296
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 11-Jul-1998


  • gravitation
  • methods, analytical
  • methods, numerical
  • galaxies, elliptical and lenticular, cD
  • galaxies, kinematics and dynamics

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