2D velocity fields of simulated interacting disc galaxies

TL;DR

This study uses simulations to analyze how galaxy interactions distort velocity fields, affecting the interpretation of galaxy dynamics and the reliability of Tully-Fisher measurements at various redshifts.

Contribution

It provides a detailed analysis of velocity field distortions in simulated interacting galaxies across redshifts, highlighting limitations for low-mass systems in current observations.

Findings

Distortions are detectable in large galaxies at intermediate redshifts.

Velocity fields of small galaxies are not significantly distorted at z~0.5 with current resolution.

High-resolution near-infrared spectroscopy is effective for studying high-redshift galaxy dynamics.

Abstract

We investigate distortions in the velocity fields of disc galaxies and their use to reveal the dynamical state of interacting galaxies at different redshift. For that purpose, we model disc galaxies in combined N-body/hydrodynamic simulations. 2D velocity fields of the gas are extracted from these simulations which we place at different redshifts from z=0 to z=1 to investigate resolution effects on the properties of the velocity field. To quantify the structure of the velocity field we also perform a kinemetry analysis. If the galaxy is undisturbed we find that the rotation curve extracted from the 2D field agrees well with long-slit rotation curves. This is not true for interacting systems, as the kinematic axis is not well defined and does in general not coincide with the photometric axis of the system. For large (Milky way type) galaxies we find that distortions are still visible at intermediate redshifts but partly smeared out. Thus a careful analysis of the velocity field is necessary before using it for a Tully-Fisher study. For small galaxies (disc scale length ~2 kpc) even strong distortions are not visible in the velocity field at z~0.5 with currently available angular resolution. Therefore we conclude that current distant Tully-Fisher studies cannot give reliable results for low-mass systems. Additionally to these studies we confirm the power of near-infrared integral field spectrometers in combination with adaptive optics (such as SINFONI) to study velocity fields of galaxies at high redshift (z~2).