A Survey of Merger Remnants II: The Emerging Kinematic and Photometric Correlations

Abstract

This paper is the second in a series exploring the properties of 51 {\it optically} selected, single-nuclei merger remnants. Spectroscopic data have been obtained for a sub-sample of 38 mergers and combined with previously obtained infrared photometry to test whether mergers exhibit the same correlations as elliptical galaxies among parameters such as stellar luminosity and distribution, central stellar velocity dispersion ($σ$$_{\circ}$), and metallicity. Paramount to the study is to test whether mergers lie on the Fundamental Plane. Measurements of $σ$$_{\circ}$ have been made using the Ca triplet absorption line at 8500 Å for all 38 mergers in the sub-sample. Additional measurements of $σ$$_{\circ}$ were made for two of the mergers in the sub-sample using the CO absorption line at 2.29 $\micron$. The results indicate that mergers show a strong correlation among the parameters of the Fundamental Plane but fail to show a strong correlation between $σ$$_{\circ}$ and metallicity (Mg$_{2}$). In contrast to earlier studies, the $σ$$_{\circ}$ of the mergers are consistent with objects which lie somewhere between intermediate-mass and luminous giant elliptical galaxies. However, the discrepancies with earlier studies appears to correlate with whether the Ca triplet or CO absorption lines are used to derive $σ$$_{\circ}$, with the latter almost always producing smaller values. Finally, the photometric and kinematic data are used to demonstrate for the first time that the central phase-space density of mergers are equivalent to elliptical galaxies. This resolves a long-standing criticism of the merger hypothesis.