Simulating multiple merger pathways to the central kinematics of early-type galaxies
Abstract
Two-dimensional integral field surveys such as ATLAS3D are producing rich observational data sets yielding insights into galaxy formation. These new kinematic observations have highlighted the need to understand the evolutionary mechanisms leading to a spectrum of fast rotators and slow rotators in early-type galaxies. We address the formation of slow and fast rotators through a series of controlled, comprehensive hydrodynamical simulations, sampling idealized galaxy merger scenarios constructed from model spiral galaxies. Idealized and controlled simulations of this sort complement the more `realistic' cosmological simulations by isolating and analysing the effects of specific parameters, as we do in this paper. We recreate minor and major binary mergers, binary merger trees with multiple progenitors, and multiple sequential mergers. Within each of these categories of formation history, we correlate progenitor gas fraction, mass ratio, orbital pericentre, orbital ellipticity, and spin with remnant kinematic properties. We create kinematic profiles of these 95 simulations comparable to ATLAS3D data. By constructing remnant profiles of the projected specific angular momentum (λ _R= < R|V|rangle / < R √{V^2+σ ^2}rangle), triaxiality, and measuring the incidences of kinematic twists and kinematically decoupled cores, we distinguish between varying formation scenarios. We find that binary mergers nearly always form fast rotators. Slow rotators can be formed from zero initial angular momentum configurations and gas-poor mergers, but are not as round as the ATLAS3D galaxies. Remnants of binary merger trees are triaxial slow rotators. Sequential mergers form round slow rotators that most resemble the ATLAS3D rotators.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2014
- DOI:
- 10.1093/mnras/stu1444
- arXiv:
- arXiv:1407.4812
- Bibcode:
- 2014MNRAS.444.1475M
- Keywords:
-
- galaxies: evolution;
- galaxies: formation;
- galaxies: interactions;
- galaxies: kinematics and dynamics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- MNRAS, in press, 12 pages, 15 figures