An H α Impression of Ly α Galaxies at z ≃ 6 with Deep JWST/NIRCam Imaging

[摘要] We present a study of seven spectroscopically confirmed (Ly α -emitting) galaxies at redshiftz≃ 6 using the JWST/NIRCam imaging data. These galaxies, with a wide range of Ly αluminosities, were recently observed in a series of NIRCam broad and medium bands. We constrain the rest-frame UV/optical continua and measure the H αline emission of the galaxies using the combination of JWST/NIRCam and archival HST/WFC3 infrared photometry. We further estimate the escape fractions of their Ly αphotons ({f}_{mathrm{esc}}^{mathrm{Ly}alpha } ) and the production efficiency of ionizing photons ( ξ _ion). Among the sample, six out of seven galaxies have Ly αescape fractions of ≲10%, which might be the status for most of the star-forming galaxies atz≃ 6. One UV-faint Ly αgalaxy with an extremely blue UV slope has a large value of {f}_{mathrm{esc}}^{mathrm{Ly}alpha }reaching ≃50%. These galaxies have a broad range ofξ _ion over log₁₀ ξ _ion,0 (Hz erg⁻¹) ∼ 25.0–26.5. We find that UV-fainter galaxies with bluer UV-continuum slopes likely have higher escape fractions of Ly αphotons. We also find that galaxies with higher Ly αline emission tend to produce ionizing photons more efficiently. The most Ly α -luminous galaxy in the sample has a very highξ _ion,0 of log₁₀ ξ _ion,0 (Hz erg⁻¹) > 26. Our results support the scenario that Ly αgalaxies may have served as an important contributor to cosmic reionization. Blue and bright Ly αgalaxies are excellent targets for JWST follow-up spectroscopic observations.