The Atlas3D project - V. The CO Tully-Fisher relation of early-type galaxies

TL;DR

This study demonstrates that CO molecules are effective tracers for the kinematic analysis of early-type galaxies, establishing a CO Tully-Fisher relation consistent with stellar kinematics and comparable to spiral galaxies, with potential for high-redshift applications.

Contribution

First demonstration of the CO Tully-Fisher relation in early-type galaxies using both single-dish and interferometric data, showing its robustness and consistency with stellar kinematics.

Findings

CO molecules are excellent kinematic tracers in high-mass galaxies.

The CO Tully-Fisher relation in early-type galaxies is offset from spirals by about 1 magnitude.

The intrinsic scatter of the relation is approximately 0.4 magnitudes.

Abstract

We demonstrate here using both single-dish and interferometric observations that CO molecules are an excellent kinematic tracer, even in high-mass galaxies, allowing us to investigate for the first time the CO Tully-Fisher relation of early-type galaxies. We compare the Tully-Fisher relations produced using both single-dish and interferometric data and various inclination estimation methods, and evaluate the use of the velocity profile shape as a criterion for selecting galaxies in which the molecular gas extends beyond the peak of the rotation curve. We show that the gradient and zero-point of the best-fit relations are robust, independent of the velocity measure and inclination used, and agree with those of relations derived using stellar kinematics. We also show that the early-type CO Tully-Fisher (CO-TF) relation is offset from the CO-TF of spirals by 0.98 \pm 0.22 magnitude at Ks-band, in line with other results. The intrinsic scatter of the relation is found to be \approx 0.4 magnitudes, similar to the level found in the spiral galaxy population. Next generation facilities such as the Large Millimeter Telescope (LMT) and the Atacama Large Millimeter/Sub-millimeter Array (ALMA) should allow this technique to be used in higher-redshift systems, providing a simple new tool to trace the mass-to-light ratio evolution of the most massive galaxies over cosmic time.