2025/01/13 by Keunho Kim, Kim, Keunho, Anahita Alavi +17
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.48550/arxiv.2501.07548
openalex publication_date 2025/01/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The mechanisms of Lyα photon escape are key to understanding galaxy evolution and cosmic reionization, yet remain poorly understood. We investigate the UV-continuum sizes of 23 Lyα emitters (LAEs) at Cosmic Noon (1.7 < z < 3.3), extending previous size analyses to include fainter galaxies (M\rm UV ≃ -14) using gravitational lensing. Our results show that these LAEs are unusually small for their luminosity, with a mean effective radius (r\rm eff) of 170 ± 140 pc. They follow a distinct size-luminosity relation, with an intercept at M\rm UV = -21 approximately three times smaller than typical star-forming galaxies (SFGs) at similar redshifts. This relation, however, is consistent with that of low-redshift Green Pea galaxies, suggesting that LAEs maintain compact sizes across redshifts. We also find that Lyα equivalent width (EW(Lyα)) increases with decreasing r\rm eff, confirming previous findings. The small sizes of LAEs lead to high star formation surface densities (ΣSFR = 1-600 M\odot \rmyr-1 \rmkpc-2), clearly separating them from typical SFGs in the ΣSFR vs. r\rm eff space. Given that high ΣSFR is linked to strong galactic outflows, our findings imply that compact morphology plays a key role in Lyα escape, likely facilitated by outflows that clear under-dense channels in the ISM. Thus, these results demonstrate that compact size and high ΣSFR can help identify Lyα-emitters.