探测IGM透射的空间变化：在$z\simeq6.2$处H$\alpha$选择的星系高密度区域中更高的Ly$\alpha$可见性
Probing Spatial Variations in IGM Transmission: Higher Ly$α$ Visibility in an H$α$-Selected Galaxy Overdensity at $z\simeq6.2$
- The University of Tokyo（东京大学）
- Peking University（北京大学）
- Waseda University（早稻田大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
利用JWST和Subaru数据，在z≈6.2的Hα星系高密度区域中发现更高的Lyα可见性，表明IGM电离状态的空间变化影响Lyα逃逸，支持大电离泡优先形成于高密度区域的假说。
AI中文摘要：
再电离时期的Ly$\alpha$发射可见性既取决于星系性质，也取决于Ly$\alpha$光子穿过星系际介质（IGM）的透射情况。利用JWST/NIRCam F470N成像，我们在CEERS天区中识别出一个显著的投影H$\alpha$发射体（HAEs）高密度区域，红移为$z\simeq6.2$。我们使用Subaru/HSC NB872成像测量其Ly$\alpha$通量，并比较了距离密度中心$2'$范围内的星系与区域外星系的Ly$\alpha$可见性。内部区域的Ly$\alpha$发射体（LAE）比例为$0.41^{+0.15}_{-0.14}$，外部区域为$0.27^{+0.19}_{-0.15}$。将H$\alpha$和Ly$\alpha$图像叠加后，内部和外部区域的中位Ly$\alpha$逃逸比例分别为$0.100^{+0.091}_{-0.053}$和$0.063^{+0.130}_{-0.063}$。这两种测量均表明内部区域的Ly$\alpha$可见性更高，尽管显著性仅为中等。靠近密度中心的HAEs系统性质量更大，UV斜率更红，这反而有利于较低的Ly$\alpha$逃逸。因此，Ly$\alpha$可见性的环境差异难以仅用底层星系群体的变化来解释。我们的结果与高密度区域中更高电离的IGM导致Ly$\alpha$衰减减少的预期一致，正如大型H\\,{\sc ii}气泡优先形成于此类星系高密度区域周围所预期的那样。大视场LAE分布为该情景提供了补充支持，因为HAE定义的密度中心与$1.4\\,{\rm deg}^2$的HSC天区中最强的LAE高密度区域重合。这些发现强调了IGM衰减的空间变化在塑造再电离末期Ly$\alpha$可见性方面的重要性。
英文摘要：
The visibility of Ly$α$ emission during the epoch of reionization depends on both galaxy properties and the transmission of Ly$α$ photons through the intergalactic medium (IGM). Using JWST/NIRCam F470N imaging, we identify a prominent projected overdensity of H$α$ emitters (HAEs) at $z\simeq6.2$ in CEERS field. We use Subaru/HSC NB872 imaging to measure their Ly$α$ fluxes and compare the Ly$α$ visibility of galaxies within $2'$ of the density center with that of galaxies outside this region. The Ly$α$-emitter (LAE) fraction is $0.41^{+0.15}_{-0.14}$ in the inner region and $0.27^{+0.19}_{-0.15}$ in the outer region. Stacking the H$α$ and Ly$α$ images gives median Ly$α$ escape fractions of $0.100^{+0.091}_{-0.053}$ and $0.063^{+0.130}_{-0.063}$ in the inner and outer regions, respectively. Both measures indicate higher Ly$α$ visibility in the inner region, although only at modest significance. HAEs closer to the density center are systematically more massive and have redder UV slopes, which instead favor lower Ly$α$ escape. The environmental difference in Ly$α$ visibility is therefore difficult to explain solely by variations in underlying galaxy population. Our results are consistent with reduced Ly$α$ attenuation through a more highly ionized IGM in the overdense region, as expected if large H\,{\sc ii} bubbles preferentially form around such galaxy overdensities. The wide-field LAE distribution provides complementary support for this scenario, as the HAE-defined density center coincides with the strongest LAE overdensity across the $1.4\,{\rm deg}^2$ HSC field. These findings highlight the importance of spatial variations in IGM attenuation in shaping Ly$α$ visibility near the end of reionization.
