A Versatile Family of Galactic Wind Models

TL;DR

This paper introduces a flexible galactic wind model incorporating various physical effects, demonstrating how radiative losses influence wind solutions and aligning model predictions with observed X-ray luminosity and star formation rate relationships.

Contribution

It presents a new versatile model of galactic outflows that includes radiative losses and extended mass distributions, improving upon previous models like Chevalier & Clegg (1985).

Findings

Radiative losses cause high-temperature winds in highly mass-loaded outflows.

Low mass-loaded winds can be driven at low temperatures near the cooling curve peak.

The model reproduces the observed linear relation between X-ray luminosity and SFR.

Abstract

We present a versatile family of model galactic outflows including non-uniform mass and energy source distributions, a gravitational potential from an extended mass source, and radiative losses. The model easily produces steady-state wind solutions for a range of mass-loading factors, energy-loading factors, galaxy mass and galaxy radius. We find that, with radiative losses included, highly mass-loaded winds must be driven at high central temperatures, whereas low mass-loaded winds can be driven at low temperatures just above the peak of the cooling curve, meaning radiative losses can drastically affect the wind solution even for low mass-loading factors. By including radiative losses, we are able to show that subsonic flows can be ignored as a possible mechanism for expelling mass and energy from a galaxy compared to the more efficient transonic solutions. Specifically, the transonic solutions with low mass-loading and high energy-loading are the most efficient. Our model also produces low-temperature, high-velocity winds that could explain the prevalence of low-temperature material in observed outflows. Finally, we show that our model, unlike the well-known Chevalier & Clegg (1985) model, can reproduce the observed linear relationship between wind X-ray luminosity and star formation rate (SFR) over a large range of SFR from $1-1000$ M$_{\odot}$/yr assuming the wind mass-loading factor is higher for low-mass, and hence, low-SFR galaxies. We also constrain the allowed mass-loading factors that can fit the observed X-ray luminosity vs. SFR trend, further suggesting an inverse relationship between mass-loading and SFR as explored in advanced numerical simulations.