The escape of Lyman photons from a young starburst:: the case of Haro 11

Lyman alpha (Ly alpha) is one of the dominant tools used to probe the star-forming galaxy population at high redshift (z). However, astrophysical interpretations of data drawn from Ly alpha alone hinge on the Ly alpha escape fraction which, due to the complex radiative transport, may vary greatly. Here, we map the Ly alpha emission from the local luminous blue compact galaxy Haro 11, a known emitter of Ly alpha and the only known candidate for low-z Lyman continuum emission. To aid in the interpretation, we perform a detailed ultraviolet and optical multiwavelength analysis and model the stellar population, dust distribution, ionizing photon budget, and star-cluster population. We use archival X-ray observations to further constrain properties of the starburst and estimate the neutral hydrogen column density. The Ly alpha morphology is found to be largely symmetric around a single young star-forming knot and is strongly decoupled from other wavelengths. From general surface photometry, only very slight correlation is found between Ly alpha and H alpha, E(B - V), and the age of the stellar population. Only around the central Ly alpha bright cluster do we find the Ly alpha/H alpha ratio at values predicted by the recombination theory. The total Ly alpha escape fraction is found to be just 3 per cent. We compute that similar to 90 per cent of the Ly alpha photons that escape do so after undergoing multiple resonance scattering events, masking their point of origin. This leads to a largely symmetric distribution and, by increasing the distance that photons must travel to escape, decreases the escape probability significantly. While dust must ultimately be responsible for the destruction of Ly alpha, it plays a little role in governing the observed morphology, which is regulated more by interstellar medium kinematics and geometry. We find tentative evidence for local Ly alpha equivalent width in the immediate vicinity of star clusters being a function of cluster age, consistent with hydrodynamic studies. We estimate the intrinsic production of ionizing photons and put further constraints of similar to 9 per cent on the escaping fraction of photons at 900 angstrom.