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 seventeen 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 powerlaw profiles and reconstruct the 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 characterise the physical and morphological properties of these LAE galaxies. From reconstructing the ultra-violet 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 to 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 disk-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 disk-like nature and possible merger scenario for the LAEs in the sample.

Observations of the Lyman-α Universe

“…Of course, the morphology of LAEs may not be a simple disk, but a disk-like shape with sub-structures on < 1 pkpc scales that are poorly understood. Clumpy structures are identified in various high-z galaxies including some LAEs (Shibuya et al 2016;Cornachione et al 2018;Ritondale et al 2019). Further studies are needed to test the viewing angle effect of the Lyα escape.…”

SHARP – VI. Evidence for CO (1–0) molecular gas extended on kpc-scales in AGN star-forming galaxies at high redshift

“…In order to obtain the source plane surface brightness distribution of both targets for the optical and NIR data, we use the pixellated source reconstruction technique developed by Vegetti & Koopmans (2009) and further improved by Ritondale et al (2019) and Rizzo et al (2018). This code models the lens potential, the surface brightness distribution of the foreground lensing galaxy and the surface brightness distribution of the background source simultaneously in a fully Bayesian framework.…”

Dark matter haloes of massive elliptical galaxies at z ∼ 0.2 are well described by the Navarro–Frenk–White profile

“…The interplay between baryon and dark matter in galaxy formation is also highlighted by the so-called 'bulge-halo conspiracy' (Treu et al 2006;Humphrey & Buote 2010;Cappellari 2016). This conspiracy refers to the nearly isothermal profiles of the total matter distribution with small scatter (∼0.1-0.2) observed within half of the half-light radii to 100 half-light radii of elliptical galaxies (e.g., from strong and weak lensing : Treu & Koopmans 2004;Gavazzi et al 2007;Auger et al 2010b;Ritondale et al 2019; from stellar dynamics: Thomas et al 2007;Tortora et al 2014;Bellstedt et al 2018). As neither of the baryonic and dark matter distributions follows a power law, fine tuning between these two distributions is required to produce the isothermal distribution for the total mass.…”