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Origin of E+A galaxies: I. Physical properties of E+A's formed from galaxy merging and interaction

K. Bekki·W. J. Couch·Y. Shioya·A. Vazdekis
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Abstract

We investigate the structural, kinematical, and spectrophotometric properties of ``E+A'' galaxies -- those with strong Balmer absorption lines but no significant [OII] emission -- using numerical simulations combined with stellar population synthesis codes. We particularly focus on the two-dimensional (2D) distributions of line-of-sight velocity, velocity dispersion, colors, line index in E+A galaxies formed via the interaction and merging of two gas-rich spirals. Our numerical simulations demonstrate that E+A elliptical galaxies formed by major galaxy merging have positive radial color gradients and negative radial H$δ$ gradients by virtue of their central poststarburst populations. Furthermore, we show that the projected kinematical and spectroscopic properties of the simulated E+A galaxies can be remarkably different for different major merger models. For example, the simulated E+A ellipticals with kinematically decoupled cores clearly show regions of strong H$δ$ absorption which are very flattened, with differences in rotation and velocity dispersion between the old and young stars. E+A ellipticals are highly likely to show more rapid rotation and a smaller central velocity dispersion in young stars than in old ones.We also provide specific predictions on the structural, kinematical, and spectrophotometric properties of young globular cluster systems in E+A's. Based on these results, we discuss the importance of spatially resolved, integral field unit spectroscopy on large (8-10m) ground-based telescopes in confirming the formation of kinematically distinct cores in elliptical galaxies produced via dissipative merging and determining the most probable physical mechanism(s) for E+A formation with disky and spheroidal morphologies.

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K. Bekki, W. J. Couch, Y. Shioya, A. Vazdekis. 2005-03-28. Origin of E+A galaxies: I. Physical properties of E+A's formed from galaxy merging and interaction. https://doi.org/10.1111/j.1365-2966.2005.08932.x

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