SAZERAC 2021 | 5B | Rebecca Bowler

The diversity of dust geometries in UV-bright z ~ 7 galaxies Rebecca Bowler Oxford To understand the impact of obscured star-formation at high-redshift requires knowledge of the spatial distribution of the dust with respect to the stars. The majority of z greater than 6 galaxies known to-date however, appear very compact (r1/2 less than 1kpc) precluding such analysis with current data. In the study we obtained deep, high-resolution ALMA observations for a sample of the brightest and most star-forming galaxies known at z ~ 7. These galaxies show highly extended clumpy/merger-driven morphologies in the rest-frame UV on scales of ~ 5kpc. We find a diversity of dust geometries in these galaxies, including both compact emission appears offset relative to the unobscured component, and extended dust emission that is co-spatial with the rest-UV light. We extracted resolved rest-frame UV colours for the sources, demonstrating a clear gradient to redder colours where we directly detect the dust. Our results show for the first time the complexity and diversity of dust emission when viewed with resolved rest-UV and IR data. We present a resolved IRX-beta relation at z = 7 for the sources, and discuss the utility of the commonly used relation when applied to resolved vs. unresolved galaxy photometry. Our results further support the predictions of cosmological galaxy formation models that dust plays a significant role in shaping the observed luminosity functions even as early as z ~ 7.