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[153.05] Kinematics and the Stellar Populations in the Halo of M86

Marcel Bergmann (University of Texas, Austin)

I have obtained very deep long-slit spectroscopy along the semi-major and semi-minor axes of the giant elliptical galaxy M86, using the Low Resolution Spectrometer on the 9.2m Hobby Eberly Telescope. I use these data to measure line of sight velocity dispersions and stellar population parameters out to ~3 r_e, over six times further out than previous integrated light studies for this galaxy. These data overlap and extend beyond the region probed by PNe studies. I will present a kinematic analysis of M86 from the very central regions out to large radii, tracing out kinematic wrinkles which are the signatures of past mergers and dynamical interaction. M86 has a kinematically decoupled core, which rotates about the photometric minor axis. The bulk of the galaxy, however, shows strong rotation about the photometric major axis, along with a declining velocity dispersion as a function of radius.

I measure radial profiles for the age and metallicity of the stellar population using combinations of the H\beta, C4668, Mgb, and absorption line indices. Tying the stellar population parameters to the dynamic history allows an estimation of the importance of new star formation during merger processes. Additionally, since the integrated light data overlaps the regions of the PNe and globular cluster populations, I will be able to compare the kinematics and chemical makeup between the bulk of the stars, the PNe, and globular clusters, to constrain the formation model for the stellar halo and globular cluster system.

This study is part of a larger project to obtain deep spectroscopy for a sample of field and cluster elliptical galaxies, to better understand their kinematic and star formation histories.

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