论文标题
JWST/NIRCAM对电源的主要贡献者的研究：紫外线$ z \ sim7-8 $星系的星形成和电离特性
A JWST/NIRCam Study of Key Contributors to Reionization: The Star-forming and Ionizing Properties of UV-faint $z\sim7-8$ Galaxies
论文作者
论文摘要
Spitzer/IRAC成像表明，最明亮的$ Z \ SIM7-8 $星系通常显示出年轻的年龄和强大的静脉线发射，暗示早期星系中的高电离效率很高。但是，IRAC的有限敏感性长期以来一直在妨碍研究Fainter的努力，而更多的人群通常认为在很大程度上负责电离。在这里，我们使用CEORS JWST/NIRCAM数据来表征116 UV-Paint（中位数M $ _ {UV} = -19.5 $）$ Z \ SIM6.5-8 $ GALAXIES。 SED通常由Young（$ \ sim $ 10-50 MYR），低质量（$ M_ \ ast \ sim10^8 \ m_ \ odot $）主导，我们发现不需要极高的恒星群体（$ \ sim10^{11} m_ \ odot $）。考虑到先前对UV-Bright（M $ _ {UV} \ SIM-22 $）$ Z \ SIM7-8 $星系的研究，我们发现特定的星星形成率在CESER中有很强的（5-10美元$ \ times $）提高的证据（5-10 $ \ times $）提高了较低的亮度（中间SSFR = 103 Gyr $^{ - 1} $）。较大的SSFR意味着在相对较大的紫外线人群中，OB恒星的贡献更大，也许表明这些星系是非常有效的电离剂（中值$ξ_{ion} = 10^{25.7} $ erg $^$^$^{ - 1} $ HZ）。尽管他们的SSFR较大，但我们发现[OIII] $+$ h $β$ ews尚无明显增加，以fainter m $ _ {uv} $（中位$ \ $ \ $ 780 $ \ MATHRING {A a} $）。如果得到确认，这可能表明我们的Ceors Galaxies很大一部分具有极低的金属（$ \ lyssim $ 3％$ z_ \ odot $），其中抑制了[OIII]的排放。另外，高电离光子逃逸部分或爆发星形史也可以削弱我们的Ceors星系子集中的Nebular线。尽管我们的大多数物体都是非常蓝色的（中值$β= -2.0 $），但我们以$ \ $ \ $ 0.5 $ l_ {uv}^\ ast $的质量确定了非常灰尘的星系（$β\ sim-1 $）的重要尾巴，这可能对$ z \ sim7-8 $ sim7-8 $ star构造速率构成速率构成速率。
Spitzer/IRAC imaging has revealed that the brightest $z\sim7-8$ galaxies often exhibit young ages and strong nebular line emission, hinting at high ionizing efficiency among early galaxies. However, IRAC's limited sensitivity has long hindered efforts to study the fainter, more numerous population often thought largely responsible for reionization. Here we use CEERS JWST/NIRCam data to characterize 116 UV-faint (median M$_{UV}=-19.5$) $z\sim6.5-8$ galaxies. The SEDs are typically dominated by young ($\sim$10-50 Myr), low-mass ($M_\ast\sim10^8\ M_\odot$) stellar populations, and we find no need for extremely high stellar masses ($\sim10^{11} M_\odot$). Considering previous studies of UV-bright (M$_{UV}\sim-22$) $z\sim7-8$ galaxies, we find evidence for a strong (5-10$\times$) increase in specific star formation rate toward lower luminosities (median sSFR=103 Gyr$^{-1}$ in CEERS). The larger sSFRs imply a more dominant contribution from OB stars in the relatively numerous UV-faint population, perhaps suggesting that these galaxies are very efficient ionizing agents (median $ξ_{ion}=10^{25.7}$ erg$^{-1}$ Hz). In spite of their much larger sSFRs, we find no significant increase in [OIII]$+$H$β$ EWs towards fainter M$_{UV}$ (median $\approx$780 $\mathring{A}$). If confirmed, this may indicate that a substantial fraction of our CEERS galaxies possess extremely low metallicities ($\lesssim$3% $Z_\odot$) where [OIII] emission is suppressed. Alternatively, high ionizing photon escape fractions or bursty star formation histories can also weaken the nebular lines in a subset of our CEERS galaxies. While the majority of our objects are very blue (median $β=-2.0$), we identify a significant tail of very dusty galaxies ($β\sim-1$) at $\approx$0.5$L_{UV}^\ast$ which may contribute significantly to the $z\sim7-8$ star formation rate density.
