The kinematic structure of merger remnants

T. J. Cox, Suvendra N. Dutta, Tiziana Di Matteo, Lars Hernquist, Philip F. Hopking, Brant Robertson, Volker Springel

Research output: Contribution to journalArticlepeer-review

314 Scopus citations

Abstract

We use numerical simulations to study the kinematic structure of remnants formed from mergers of equal-mass disk galaxies. In particular, we show that remnants of dissipational mergers, which include the radiative cooling of gas, star formation, feedback from supernovae, and the growth of supermassive black holes, are smaller, rounder, have, on average, a larger central velocity dispersion, and show significant rotation compared to remnants of dissipationless mergers. The increased rotation speed of dissipational remnants owes its origin to star formation that occurs in the central regions during the galaxy merger. We have further quantified the anisotropy, three-dimensional shape, minor-axis rotation, and isophotal shape of each merger remnant, finding that dissipational remnants are more isotropic, closer to oblate, have the majority of their rotation along their major axis, and are more disky than dissipationless remnants. Individual remnants display a wide variety of kinematic properties. A large fraction of the dissipational remnants are oblate isotropic rotators. Many dissipational remnants, and all of the dissipationless ones, are slowly rotating and anisotropic. The remnants of gas-rich major mergers can well reproduce the observed distribution of projected ellipticities, rotation parameter (V/σ)*, kinematic misalignments, ψ, and isophotal shapes. The dissipationless remnants are a poor match to this data. We also investigate the properties of merger remnants as a function of initial disk gas fraction, orbital angular momentum, and the mass of the progenitor galaxies. Our results support the merger hypothesis for the origin of low-luminosity elliptical galaxies provided that the progenitor disks are sufficiently gas-rich, however our remnants are a poor match to the bright ellipticals that are slowly rotating and uniformly boxy.

Original languageEnglish (US)
Pages (from-to)791-811
Number of pages21
JournalAstrophysical Journal
Volume650
Issue number2 I
DOIs
StatePublished - Oct 20 2006

Keywords

  • Galaxies: elliptical and lenticular, cD
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: interactions
  • Methods: n-body simulations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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