The Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS)

Abstract

Aims. We present the Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS) selected from MUSE and HST observations of 17 lensing clusters. The sample consists of 603 continuum-faint (-23<M UV <-14) lensed Lyman-α emitters (producing 959 images) with secure spectroscopic redshifts between 2.9 and 6.7. Combining the power of cluster magnification with 3D spectroscopic observations, we are able to reveal the resolved morphological properties of 268 Lyman-α emitters. Methods. We use a forward modelling approach to model both Lyman-α and rest-frame UV continuum emission profiles in the source plane and measure spatial extent, ellipticity and spatial offsets between UV and Lyman-α emission. Results. We find a significant correlation between UV continuum and Lyman-α spatial extent. Our characterization of the Lyman-α haloes indicates that the halo size is linked to the physical properties of the host galaxy (SFR, Lyman-α equivalent width and Lyman-α line FWHM). We find that 48% of Lyman-α haloes are best-fitted by an elliptical emission distribution with a median axis ratio of q = 0.48. We observe that 60% of galaxies detected both in UV and Lyman-α emission show a significant spatial offset (∆ Lyα−UV ). We measure a median offset of ∆ Lyα−UV = 0.58 ± 0.14 kpc for the entire sample. By comparing the spatial offset values with the size of the UV component, we show that 40% of the offsets could be due to star-forming sub-structures in the UV component, while the larger offsets (60%) are more likely due to larger distance processes such as scattering effects inside the circumgalactic medium or emission from faint satellites or merging galaxies. Comparisons with a zoom-in radiative hydrodynamics simulation of a typical Lyman-α emitting galaxy show a very good agreement with LLAMAS galaxies and indicate that bright star-formation clumps and satellite galaxies could produce a similar spatial offsets distribution.

Scrutiny of a very young, metal-poor star-forming Lyα emitter at z ≈ 3.7

“…One possible solution to solve this puzzle is through the study of strongly lensed LAEs (e.g. Swinbank et al 2007 ;Karman et al 2015 ;Caminha et al 2016 ;Patr ício et al 2016 ;Vanzella et al 2016Vanzella et al , 2020Smit et al 2017 ;Claeyssens et al 2019Claeyssens et al , 2022Chen et al 2021 ;Iani et al 2021 ). In fact, both lensing effects of magnification and stretching can allow to reach faint fluxes and small scales in short observing time, even though robust lensing models have to be developed in order to correctly interpret and compare the results.…”

The miniJPAS Survey: Detection of the double-core Lyα morphology for two high-redshift QSOs

“…Erb et al (2019) explained the offset by a significant variation of the neutral hydrogen column density across the object. Chen et al (2021) identified 2 Lyα nebulae spatially offset from the associated star-forming regions, suggesting large spatial fluctuations in the gas properties (see also Claeyssens et al 2022). Borisova et al (2016) found no evidence for "bipolar ionization cone illumination" patterns in their study of Lyα nebulae around quasars, except for one quasar (see their Section.…”

Dissecting the interstellar medium of a z = 6.3 galaxy

“…A similar consideration can be applied to the centroid/peak difference between the Lyman-α and the UV galaxy emission, supposing that the UV light is traced by the afterglow position. Indeed Claeyssens et al (2022) report a centroid/peak difference of several kiloparsecs. However, the velocity shift is extremely high if the Lyman-α emission comes from the same galaxy producing the absorption lines (even supposing a shift between the absorption line and the systemic redshift of the galaxy).…”