Unveiling the σ-discrepancy. II. Revisiting the Evolution of ULIRGs and the Origin of Quasars

Abstract

We present the first central velocity dispersions (σ_circle) measured from the 0.85 μm Calcium II Triplet (CaT) for eight advanced (i.e., single nuclei) local (z <= 0.15) Ultraluminous Infrared Galaxies (ULIRGs). First, these measurements are used to test the prediction that the "σ-Discrepancy," in which the CaT σ_circle is systematically larger than the σ_circle obtained from the 1.6 or 2.3 μm stellar CO band-heads, extends to ULIRG luminosities. Next, we combine the CaT data with rest-frame I-band photometry obtained from archival Hubble Space Telescope data and the Sloan Digital Sky Survey (SDSS) to derive dynamical properties for the eight ULIRGs. These are then compared to the dynamical properties of 9255 elliptical galaxies from the SDSS within the same redshift volume and of a relatively nearby (z < 0.4) sample of 53 QSO host galaxies. A comparison is also made between the I-band and H-band dynamical properties of the ULIRGs. We find four key results: (1) the σ-Discrepancy extends to ULIRG luminosities; (2) at I-band ULIRGs lie on the fundamental plane in a region consistent with the most massive elliptical galaxies and not low-intermediate mass ellipticals as previously reported in the near-infrared; (3) the I-band M/L of ULIRGs are consistent with an old stellar population, while at H-band ULIRGs appear significantly younger and less massive; and (4) we derive an I-band Kormendy Relation from the SDSS ellipticals and demonstrate that ULIRGs and QSO host galaxies are dynamically similar.