Journal
ASTROPHYSICAL JOURNAL
Volume 685, Issue 2, Pages 897-903Publisher
IOP PUBLISHING LTD
DOI: 10.1086/591632
Keywords
galaxies : elliptical and lenticular, cD; galaxies : evolution; galaxies : formation; galaxies : kinematics and dynamics; galaxies : structure; methods : n-body simulations
Categories
Funding
- DFG Sonderforschungsbereich 375
- Origin and Structure of the Universe
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The intrinsic anisotropy delta and flattening epsilon of simulated merger remnants is compared with elliptical galaxies that have been observed by the SAURON collaboration, and that were analyzed using axisymmetric Schwarzschild models. Collisionless binary mergers of stellar disks and disk mergers with an additional isothermal gas component, neglecting star formation, cannot reproduce the observed trend delta = 0.55 epsilon (SAURON relationship). An excellent fit of the SAURON relationship for flattened ellipticals with epsilon >= 0.25 is, however, found for merger simulations of disks with gas fractions >= 20%, including star formation and stellar energy feedback. Massive black hole feedback does not strongly affect this result. Subsequent dry merging of these merger remnants does not generate the slowly rotating SAURON ellipticals, which are characterized by low ellipticities epsilon < 0.25 and low anisotropies. These objects therefore might not have been shaped by a final major merger of either early-type galaxies or disks. We show, however, that stellar spheroids resulting from multiple, hierarchical mergers of star-bursting subunits in a cosmological context are in excellent agreement with the low ellipticities and anisotropies of the slowly rotating SAURON ellipticals and their observed trend of delta with epsilon. The numerical simulations indicate that the SAURON relation might be a result of strong violent relaxation and phase mixing of multiple, kinematically cold stellar subunits, with the angular momentum of the system determining its location on the relation.
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