Predicting Lyman-alpha escape fractions with a simple observable: Lyman-alpha in emission as an empirically calibrated star formation rate indicator

Understand

Lyman-alpha (Lya) is intrinsically the brightest line emitted from active galaxies.

• While it originates from many physical processes, for star-forming galaxies the intrinsic Lya luminosity is a direct tracer of the Lyman-continuum (LyC) radiation produced by the most massive O- and early-type B-stars with lifetimes of a few Myrs.
• As such, Lya luminosity should be an excellent instantaneous star formation rate (SFR) indicator.
• However, its resonant nature and susceptibility to dust as a rest-frame UV photon makes Lya very hard to interpret due to the uncertain Lya escape fraction, f$_{esc,Ly\alpha}$.