Scaling Relations of Starburst-Driven Galactic Winds

TL;DR

This study uses 3D simulations to analyze how starburst-driven galactic wind velocities relate to star formation rates and gas temperatures, revealing complex scaling behaviors and underestimations in observed velocities.

Contribution

It introduces a detailed analysis of wind velocity scaling relations from simulations, highlighting the dependence on temperature regimes and the impact on observational estimates.

Findings

Strong correlation between wind velocity and SFR until flattening point.

Neutral gas velocities are significantly lower than hot gas velocities.

Absorption lines of neutral gas underestimate hot gas outflow energetics.

Abstract

Using synthetic absorption lines generated from 3D hydro-dynamical simulations we explore how the velocity of a starburst-driven galactic wind correlates with the star formation rate (SFR) and SFR density. We find strong correlations until the scaling relations flatten abruptly at a point set by the mass loading of the starburst. Below this point the scaling relation depends on the temperature regime being probed by the absorption line, not on the mass loading. The exact scaling relation depends on whether the maximum or mean velocity of the absorption line is used. We find that the outflow velocity of neutral gas is four to five times lower than the average velocity of the hottest gas, with the difference in velocity between the neutral and ionized gas increasing with gas ionization. Thus, absorption lines of neutral or low ionized gas will underestimate the outflow velocity of hot gas, severely underestimating outflow energetics.