We report the discovery of a spectroscopically confirmed strong Lyα emitter at z = 7.0281 0.0003, observed as part of the Reionization Lensing Cluster Survey (RELICS). This galaxy, dubbed “Dichromatic Primeval Galaxy” at z ∼ 7 (DP7), shows two distinct components. While fairly unremarkable in terms of its ultraviolet (UV) luminosity (, where is the characteristic luminosity), DP7 has one of the highest observed Lyα equivalent widths (EWs) among Lyα emitters at z > 6 (>200 Å in the rest frame). The strong Lyα emission generally suggests a young metal-poor, low-dust galaxy; however, we find that the UV slope β of the galaxy as a whole is redder than typical star-forming galaxies at these redshifts, −1.13 0.84, likely indicating, on average, a considerable amount of dust obscuration, or an older stellar population. When we measure β for the two components separately, however, we find evidence of differing UV colors, suggesting two separate stellar populations. Also, we find that Lyα is spatially extended and likely larger than the galaxy size, hinting to the possible existence of a Lyα halo. Rejuvenation or merging events could explain these results. Either scenario requires an extreme stellar population, possibly including a component of Population III stars, or an obscured active galactic nucleus. DP7, with its low UV luminosity and high Lyα EW, represents the typical galaxies that are thought to be the major contribution to the reionization of the universe, and for this reason DP7 is an excellent target for follow-up with the James Webb Space Telescope.

我们报告在z = 7.0281 0.0003处发现了一个经光谱证实的强 Ly α发射器，作为再电离透镜集群调查 (RELICS) 的一部分观察到。这个星系被称为z ∼ 7 (DP7)处的“双色原初星系” ，显示出两个不同的组成部分。虽然就其紫外 (UV) 光度（，特征光度）而言相当不起眼，但 DP7在z > 6 的Ly α发射体中具有最高的观测到的 Ly α等效宽度（EW）之一（其余的 >200 Å）框架）。强烈的 Ly α发射通常表明一个年轻的贫金属、低尘埃星系；然而，我们发现 UV 斜率β在这些红移处，整个星系的红度比典型的恒星形成星系更红，-1.13 0.84，这可能表明，平均而言，有相当数量的尘埃遮蔽，或较老的恒星种群。然而，当我们分别测量这两个分量的β时，我们发现了不同紫外线颜色的证据，表明存在两个独立的恒星群。此外，我们发现 Ly α在空间上延伸并且可能大于星系大小，暗示可能存在 Ly α晕。复兴或合并事件可以解释这些结果。任何一种情况都需要极端的恒星群，可能包括第三族群恒星的一部分，或者一个被遮蔽的活动星系核。DP7，具有低紫外光度和高 Ly α EW，代表被认为是对宇宙再电离的主要贡献的典型星系，因此 DP7 是詹姆斯韦伯太空望远镜后续跟踪的绝佳目标。