Lyman-alpha radiation pressure: an analytical exploration

Abstract

We study radiation pressure due to Lyman alpha line photons, obtaining and exploring analytical expressions for the force-multiplier, $M_F(N_H,Z)=F_{\alpha }/(L_{\alpha }/c)$, as a function of gas column density, $N_H$, and metallicity, $Z$, for both dust-free and dusty media, employing a WKB approach for the latter case. Solutions for frequency offset emission to emulate non-static media moving with a bulk velocity $v$, have also been obtained. We find that, in static media, Ly$\alpha$ pressure dominates over both photoionization and dust-mediated UV radiation pressure in a very wide parameter range ($16<\log N_H<23$; $-4<\log [Z/Z_{\odot }]<0$). For example, it overwhelms the other two forces by 10 (300) times in standard (low-$Z$) star-forming clouds. Thus, in agreement with previous studies, we conclude that Ly$\alpha$ pressure plays a dominant role in the initial acceleration of the gas around luminous sources, and must be implemented in galaxy formation, evolution and outflow models and simulations.

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Cited by in corpus (3)

• A systematic study of the escape of LyC and Ly$\alpha$ photons from star-forming, magnetized turbulent clouds
• TODDLERS: A new UV-mm emission library for star-forming regions. 1. Integration with SKIRT and public release
• Impact of Radiation Feedback on the Formation of Globular Cluster Candidates during Cloud-Cloud Collisions