The Structure and Evolution of Interacting Binary Galaxies

Astronomy, Galaxies, Mergers, Galaxy Evolution, Colliding Galaxies, Numerical Simulations, Merging Galaxies

Borne, Kirk Daniel ; Gunn, James E.

University:California Institute of Technology

Department:Physics, Mathematics and Astronomy

关键词: Astronomy, Galaxies, Mergers, Galaxy Evolution, Colliding Galaxies, Numerical Simulations, Merging Galaxies;   

Others  :  https://thesis.library.caltech.edu/3390/3/Borne_kd_1983.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

A numerical code has been constructed for the study of the evolution of interacting binary galaxies. This "multiple three-body" algorithm (MTBA) essentially involves N concurrent three-body integrations; it is the sum of the interactions of the perturber with each of the N particles comprising the primary "galaxy" that determines the binary orbital evolution. MTBA incorporates a violent relaxation phase that allows the particles to redistribute themselves in the gravitational field of the perturber prior to the full binary orbital evolution calculation. This redistribution is important for systems with an initially strong tidal potential; their predicted merger times are 50-100% larger than previously estimated. Tabulated merger times for both circular and elliptical orbits demonstrate that typical close binary galaxies will merge in about twice their initial binary orbital periods, roughly 10⁹ years. This timescale depends strongly on the binary separation, weakly on its mass ratio, and less on initial galaxy rotation than has heretofore been suggested.

A specific interacting binary simulation is described in detail in the first paper. Surface brightness maps, structural parameters, and rotation properties are described at various times during the evolution, followed by a discussion of the properties of the merger remnant. Many of the results reported here are consistent with those obtained from the larger, more expensive N-body simulations.

For the second paper, MTBA is altered so that each "galaxy" is represented by a configuration of test particles. Simulated tidal interactions between these "galaxies" are matched to the measured properties of real binaries in an effort to determine the physical state of each observed pair. The catalog of isolated galaxy pairs prepared by Karachentsev has been culled for its E-E constituents. CCD pictures and long-slit spectroscopic observations have been obtained at KPNO for the most photometrically distorted of these systems. Such pairs very likely represent strongly interacting, physically associated, binary elliptical galaxies. Radial variations of rotation velocity and velocity dispersion are extracted from the spectroscopic data for each of the two galaxies in a given pair. The combined spectroscopic and photometric data for that binary can be reproduced by an appropriate projection of a particular numerical simulation of the system. Some constraints can be placed on the masses of the galaxies, their internal dynamical configurations, and the properties of their relative orbit, including the three-dimensional orientation of the pair. Detailed results are presented for two pairs, K99 and K564. NGC 1587, the brighter component of K99, has the highest rotation rate known for an E2 galaxy, with a value v_rot/σ = 0.6.