We use new Hubble Space Telescope (HST) images of nine Green Pea galaxies (GPGs) to study their resolved structure and color. The choice of filters, F555W and F850LP, together with the redshift of the galaxies (z ∼ 0.25), minimizes the contribution of the nebular [O iii] and Hα emission lines to the broadband images. While these galaxies are typically very blue in color, our analysis reveals that it is only the dominant stellar clusters that are blue. Each GPG does clearly show the presence of at least one bright and compact star-forming region, but these are invariably superimposed on a more extended and lower surface brightness emission. Moreover, the colors of the star-forming regions are on average bluer than those of the diffuse emission, reaching up to 0.6 magnitudes bluer. Assuming that the diffuse and compact components have constant and single-burst star formation histories, respectively, the observed colors imply that the diffuse components (possibly the host galaxy of the star formation episode) have, on average, old stellar ages (>1 Gyr), while the star clusters are younger than 500 Myr. While a redder stellar component is perhaps the most plausible explanation for these results, the limitations of our current data set lead us to examine possible alternative mechanisms, particularly recombination emission processes, which are unusually prominent in systems with such strong line emission. With the available data, however, it is not possible to distinguish between these two interpretations. A substantial presence of old stars would indicate that the mechanisms allowing large escape fractions in these local galaxies may be different from those at play during the reionization epoch.

我们使用九个绿豆星系 (GPG) 的新哈勃太空望远镜 (HST) 图像来研究它们解析的结构和颜色。F555W 和 F850LP 滤波器的选择，加上星系的红移 ( z ∼ 0.25)，最大限度地减少了星云 [O iii ] 和 H α的贡献发射线到宽带图像。虽然这些星系的颜色通常很蓝，但我们的分析表明，只有占主导地位的星团是蓝色的。每个 GPG 确实清楚地显示了至少一个明亮而致密的恒星形成区域的存在，但这些区域总是叠加在更广泛和更低的表面亮度发射上。此外，恒星形成区域的颜色平均比漫射发射的颜色更蓝，达到更蓝 0.6 级。假设弥散分量和致密分量分别具有恒定和单次爆发的恒星形成历史，观察到的颜色意味着弥散分量（可能是恒星形成事件的宿主星系）平均具有古老的恒星年龄（>1 Gyr )，而星团的年龄小于 500 Myr。虽然较红的恒星成分可能是对这些结果最合理的解释，但我们当前数据集的局限性使我们研究了可能的替代机制，尤其是复合发射过程，这些过程在具有如此强线发射的系统中异常突出。然而，根据现有数据，无法区分这两种解释。大量老恒星的存在表明，这些局部星系中允许大量逃逸部分的机制可能与再电离时期发挥作用的机制不同。这在具有如此强线发射的系统中异常突出。然而，根据现有数据，无法区分这两种解释。大量老恒星的存在表明，这些局部星系中允许大量逃逸部分的机制可能与再电离时期发挥作用的机制不同。这在具有如此强线发射的系统中异常突出。然而，根据现有数据，无法区分这两种解释。大量老恒星的存在表明，这些局部星系中允许大量逃逸部分的机制可能与再电离时期发挥作用的机制不同。