The properties of lensed high redshift Lyman-alpha emitters

The circumgalactic medium (CGM) is closely linked to galaxy formation and evolution, but difficult to observe in emission at high redshift. I will present some first results from the Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS), a large sample of >600 lensed Lyman-alpha emitters (LAEs) observed with MUSE and HST towards massive galaxy clusters. Thanks to the strong lensing magnification and associated gain in spatial resolution, we can detect and characterize very faint galaxies, and the resolved properties of line emission from the circumgalactic medium (CGM). With such a statistical sample we can characterize Lyman-alpha haloes as small as 0.5 kpc (correcting for the lensing effect) and measure their intrinsic morphological properties such as extent, ellipticity, as well as the UV morphology and spatial offsets between the UV continuum and the Lyman-alpha emission. LLAMAS provides unique measurements on such properties at this redshift, beyond the reach of non-lensed deep fields, and are therefore crucial for understanding the CGM properties at z>3.