UV & Lyα halos of Lyα emitters across environments at z = 2.84

speaker: Satoshi Kikuta

Abstract :

We present UV & Lyα radial surface brightness (SB) profiles of Lyα emitters (LAEs) at z = 2.84 detected with the Hyper Suprime-Cam (HSC) on the Subaru Telescope. The depth of our data, together with the wide field coverage including a protocluster, enable us to study the dependence of Lyα halos
(LAHs) on various galaxy properties, including Mpc-scale environments. UV and Lyα images of 3490 LAEs are extracted, and stacking the images yields SB sensitivity of ~1e-20 erg/s/cm^2/arcsec^2 in Lyα. Fitting of the two-component exponential function gives the scalelengths of 1.56 and 10.4 pkpc.
Dividing the sample according to their photometric properties, we find that while the dependence of halo scalelength on environment outside of the protocluster core is not clear, LAEs in the central regions of protoclusters have very large LAHs and may be related to diffuse Lyα emission from abundant cool
gas permeating the forming protocluster core irradiated by active members including a hyperluminous QSO. For the first time, we identify “UV halos” around bright LAEs which are probably due to a few lower-mass satellite galaxies. Through comparison with recent numerical simulations, we conclude
that, while scattered Lyα photons from the host galaxies are the dominant contributor to LAHs, star formation in satellites evidently contributes significantly to LAHs, and that fluorescent Lyα emission may be boosted within protocluster cores at cosmic noon and/or near bright QSOs.