Through the Veil: Lyα Illuminates the Host Galaxies of Little Red Dots

Little Red Dots (LRDs) are enigmatic, compact red sources ubiquitous in JWST deep fields whose physical nature remains elusive. As one of the most sensitive tracers of neutral hydrogen in galaxy environments, Ly$\alpha$ is uniquely positioned to probe the gaseous structures proposed to explain LRDs' unusual properties. We present a systematic study of Ly$\alpha$ emission in LRDs, using a sample of 110 spectroscopically confirmed LRDs at $z \geq 4$ from the A. de Graaff et al. (2025) catalog, all with NIRSpec/PRISM coverage of the Ly$\alpha$ line. We detect Ly$\alpha$ at signal-to-noise S/N $\geq$ 3 in 32 LRDs, finding Ly$\alpha$ luminosities and the distribution of rest-frame equivalent widths consistent with normal star-forming galaxies at comparable redshifts. Yet the Ly$\alpha$/H$\alpha$ ratios fall systematically below those of star-forming galaxies, and the Ly$\alpha$ luminosity tracks [O III] luminosity more closely than [O III] equivalent width, together suggesting that Ly$\alpha$ is primarily associated with the host-scale component rather than the compact component responsible for the broad Balmer lines and red continuum. For 13 LRDs at $z \gtrsim 5.5$, we construct continuum-subtracted Ly$\alpha$ maps using broadband imaging from HST/ACS or JWST/NIRCam, revealing spatially extended, asymmetric, and often offset emission relative to the rest-optical light, consistent with resonant scattering through clumpy, anisotropic gas commonly observed in high-redshift Ly$\alpha$ emitters. These results support a two-component picture in which the compact rest-optical source is embedded within a more extended host-galaxy environment whose interstellar and circumgalactic gas shapes Ly$\alpha$ escape and spatial redistribution. Ly$\alpha$ opens a new window into the relation between the compact red component, the host galaxy, and the surrounding gas in LRDs.