Connecting Galaxy Disk and Extended Halo Gas Kinematics

TL;DR

This study investigates the relationship between galaxy disk and halo gas kinematics, revealing that halo gas velocities are generally not coupled with galaxy rotation, and uses simulations to interpret these observations.

Contribution

It provides new observational evidence that halo gas is often decoupled from galaxy rotation and employs cosmological simulations to understand this dynamic interaction.

Findings

Halo gas velocities are mostly not consistent with galaxy rotation.

Mechanisms other than co-rotation, like inflow and feedback, influence halo gas kinematics.

Simulations support observational results and help interpret halo gas dynamics.

Abstract

We have explored the galaxy disk/extended halo gas kinematic relationship using rotation curves (Keck/ESI) of ten intermediate redshift galaxies which were selected by MgII halo gas absorption observed in quasar spectra. Previous results of six edge-on galaxies, probed along their major axis, suggest that observed halo gas velocities are consistent with extended disk-like halo rotation at galactocentric distances of 25-72 kpc. Using our new sample, we demonstrate that the gas velocities are by and large not consistent with being directly coupled to the galaxy kinematics. Thus, mechanisms other than co-rotation dynamics (i.e., gas inflow, feedback, galaxy-galaxy interactions, etc.) must be invoked to account for the overall observed kinematics of the halo gas. In order to better understand the dynamic interaction of the galaxy/halo/cosmic web environment, we performed similar mock observations of galaxies and gaseous halos in Lambda-CDM cosmological simulations. We discuss an example case of a z=0.92 galaxy with various orientations probing halo gas at a range of positions. The gas dynamics inferred using simulated quasar absorption lines are consistent with observational data.