Lyman-alpha in a fog

In “From Mirrors to Windows: Lyman-alpha Radiative Transfer in a Very Clumpy Medium” (ApJL, 833 (2), L26, 5 pp., 2016), and “Resonant line transfer in a fog: Using Lyman-alpha to probe tiny structures in atomic gas” we describe the impact of very clumpy medium on Lyman-α (Lyα) radiative transfer.

We found that depending on the number of clumps along the line-of-sight (fc), Lyα photons escape via random-walk, single-flight or excursion. Below are three animations from our radiative transfer simulation visualising each escape mechanism – can you guess which panel belongs to which mechanism?

As a small help the color coding shows the current frequency of the photon (in units of Doppler widths from line center), and the text below shows also the total number of scattering events, and the distance travelled. Each escape path will lead to a different Lyα spectrum which in turn can tell us about the structure of the ISM, and CGM.