Velocities of warm galactic outflows from synthetic H{\alpha} observations of star-forming galaxies

TL;DR

This study uses high-resolution simulations to analyze Hα emission line profiles in star-forming galaxies at z=2, revealing common blueshifted outflows extending above the disc, with implications for understanding galactic winds.

Contribution

It introduces a method to generate realistic Hα line profiles from simulations, accounting for temperature and dust effects, and compares them with observations to study galactic outflows.

Findings

Blueshifted outflows are prevalent and extend several kpc above galaxy discs.

High-velocity material often remains confined within the disc at small radii.

Hα line profiles can be modeled as a sum of two Gaussians, matching observed features.

Abstract

The velocity structure imprinted in the H{\alpha} emission line profiles contains valuable information about galactic outflows. Using a set of high-resolution zoom-in cosmological simulations of galaxies at z=2, we generate H{\alpha} emission line profiles, taking into account the temperature-dependent H{\alpha} emissivity, as well as dust extinction. The H{\alpha} line can be described as a sum of two gaussians, as typically done with observations. In general, its properties are in good agreement with those observed in local isolated galaxies with similar masses and star formation rates, assuming a spatially constant clumping factor of c=24. Blueshifted outflows are very common in the sample. They extend several kpc above the galaxy discs. They are also spread over the full extent of the discs. However, at small radii, the material with high velocities tends to remain confined within a thick disc, as part of galactic fountains or a turbulent medium, most probably due to the deeper gravitational potential at the galaxy centre.