Lyman Alpha Driven Outflows Around Star Forming Galaxies

TL;DR

This paper uses Monte-Carlo simulations to show that Lyman Alpha radiation pressure can drive powerful outflows in the early universe's galaxies and intergalactic medium, influencing galaxy evolution.

Contribution

It provides the first detailed calculations demonstrating Lyman Alpha radiation pressure's role in driving outflows across different cosmic epochs.

Findings

Lya radiation pressure can exceed gravity in the neutral IGM around minihalos.

It may drive supersonic winds in the interstellar medium of star-forming galaxies.

Lya radiation pressure could influence galaxy evolution at redshifts below 6.

Abstract

We present accurate Monte-Carlo calculations of Lyman Alpha (hereafter Lya) radiation pressure in a range of models which represent galaxies during various epochs of our Universe. We show that the radiation force that Lya photons exert on hydrogen gas in the neutral intergalactic medium (IGM), that surrounds minihalos that host the first stars, may exceed gravity by orders of magnitude and drive supersonic winds. Lya radiation pressure may also dominate over gravity in the neutral IGM that surrounds the HII regions produced by the first galaxies. However, the radiation force is likely too weak to result in supersonic outflows in this case. Furthermore, we show that Lya radiation pressure may drive outflows in the interstellar medium of star forming galaxies that reach hundreds of km/s. This mechanism could also operate at lower redshifts z<6, and may have already been indirectly detected in the spectral line shape of observed Lya emission lines.