Resolving on 100 pc scales the UV-continuum in Lyman-α emitters between redshift 2 and 3 with gravitational lensing

Abstract

We present a study of 17 LAEs at redshift 2 < z < 3 gravitationally lensed by massive early-type galaxies (ETGs) at a mean redshift of approximately 0.5. Using a fully Bayesian grid-based technique, we model the gravitational lens mass distributions with elliptical power-law profiles and reconstruct the ultraviolet (UV)-continuum surface-brightness distributions of the background sources using pixellated source models. We find that the deflectors are close to, but not consistent with isothermal models in almost all cases, at the 2σ level. We take advantage of the lensing magnification (typically μ 20) to characterize the physical and morphological properties of these LAE galaxies. From reconstructing the ultraviolet continuum emission, we find that the star formation rates range from 0.3 to 8.5 M yr−1 and that the galaxies are typically composed of several compact and diffuse components, separated by 0.4–4 kpc. Moreover, they have peak star formation rate intensities that range from 2.1 to 54.1 M yr−1 kpc−2. These galaxies tend to be extended with major axis ranging from 0.2 to 1.8 kpc (median 561 pc), and with a median ellipticity of 0.49. This morphology is consistent with disc-like structures of star formation for more than half of the sample. However, for at least two sources, we also find off-axis components that may be associated with mergers. Resolved kinematical information will be needed to confirm the disc-like nature and possible merger scenario for the LAEs in the sample.