Small-scale Intensity Mapping: Extended Lyα, Hα, and Continuum Emission as a Probe of Halo Star Formation in High-redshift Galaxies

Abstract

Abstract Lyα halos are observed ubiquitously around star-forming galaxies at high redshift, but their origin is still a matter of debate. We demonstrate that the emission from faint unresolved satellite sources, , clustered around the central galaxies may play a major role in generating spatially extended Lyα, continuum (UV + VIS), and Hα halos. We apply the analytic formalism developed in Mas-Ribas & Dijkstra to model the halos around Lyman Alpha Emitters (LAEs) at z = 3.1, for several different satellite clustering prescriptions. In general, our UV and Lyα surface brightness profiles match the observations well at physical kpc from the centers of LAEs. We discuss how our profiles depend on various model assumptions and how these can be tested and constrained with future Hα observations by the James Webb Space Telescope (JWST). Our analysis shows how spatially extended halos constrain (i) the presence of otherwise undetectable satellite sources, (ii) the integrated, volumetric production rates of Lyα and LyC photons, and (iii) their population-averaged escape fractions. These quantities are all directly relevant for understanding galaxy formation and evolution and, for high enough redshifts, cosmic reionization.