Affiliation: University of Oxford

Contribution: Poster

Title: The most luminous Lyman-break galaxies with degree-scale imaging

Abstract: The unparalleled near-infrared (NIR) capabilities of JWST have revolutionised high-redshift astronomy by finding an abundance of luminous (L ~ L*) Lyman-break galaxies (LBGs) at z>8. However, degree-scale imaging is vital to probe ultra-luminous (L >> L*) sources due to their low surface density. A challenge that faces such ground-based photometric searches for high-redshift galaxies is contamination by cool Galactic dwarf stars. I will present results using the deepest degree-scale imaging surveys prior to Euclid, such as HSC-SSP, VIDEO and UltraVISTA. We show that NIR imaging is vital for the removal of dwarf contaminants. We find an excess of bright sources at z>6 in the rest-frame UV luminosity function, signalling a lack of mass quenching and/or dust obscuration at early cosmic time in star-forming galaxies. Since ground-based imaging is seeing-dominated, ground-selected LBGs also present an unbiased sampling of the morphology and size distributions of luminous sources when viewed through the lens of JWST. Using the PRIMER survey to measure sizes of z=3-5 sources with NIRCam, we find that bright LBGs remain relatively compact with typical sizes of Re=0.7-0.9 kpc. Both parametric and non-parametric size fitting are used to compare like-for-like with simulations such as FLARES, which predict centrally concentrated star formation at high-redshift. We find good agreement with these simulations, providing tentative evidence for this result. I will also present early results from Euclid; by combining data from ground-based observatories, the overlapping photometric filters provide rich constraining power on the nature of dropout sources at z>6.

This contribution can be found in the Poster Hall.