Title: CEERS Key Paper IV: Galaxies at $4 < z < 9$ are Bluer than They Appear -- Characterizing Galaxy Stellar Populations from Rest-Frame $\sim 1$ micron Imaging Show Chinese title

Title: CEERS关键论文IV：$4 < z < 9$的星系比看起来更蓝——基于rest-frame$\sim 1$微米成像的恒星群体特征分析

Abstract: We present results from the Cosmic Evolution Early Release Survey (CEERS) on the stellar-population parameters for 28 galaxies with redshifts $4<z<9$ using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 $\mu$m data extend the coverage of the rest-frame spectral-energy distribution (SED) to nearly 1 micron for galaxies in this redshift range. By modeling the galaxies' SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 \r{A}) $-$ $I$-band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower (stellar)-mass-to-light ratios. The MIRI data reduce the stellar masses by $\langle \Delta\log M_\ast\rangle=0.25$ dex at $4<z<6$ (a factor of 1.8) and 0.37 dex at $6<z<9$ (a factor of 2.3). This also reduces the star-formation rates (SFRs) by $\langle \Delta\log\mathrm{SFR} \rangle=0.14$ dex at $4<z<6$ and 0.27 dex at $6<z<9$. The MIRI data also improve constraints on the allowable stellar mass formed in early star-formation. We model this using a star-formation history that includes both a "burst' at $z_f=100$ and a slowly varying ("delayed-$\tau$") model. The MIRI data reduce the allowable stellar mass by 0.6 dex at $4<z< 6$ and by $\approx$1 dex at $6<z<9$. Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early universe ($z\approx9$). Therefore, observations of rest-frame $\gtrsim$1 $\mu$m are paramount for constraining the stellar-mass build-up in galaxies at very high-redshifts. Show Chinese abstract

Abstract: 我们展示了来自宇宙演化早期发布巡天（CEERS）的关于28个红移为$4<z<9$的星系恒星群体参数的结果，使用了詹姆斯韦伯太空望远镜（JWST）中红外仪器（MIRI）的成像数据，并结合哈勃太空望远镜和斯皮策太空望远镜的数据。 JWST/MIRI 的5.6和7.7 $\mu$米数据将该红移范围内星系的静止框架光谱能量分布（SED）扩展到了接近1微米的覆盖范围。 通过建模这些星系的SED，MIRI的数据表明这些星系的静止框架紫外（1600 Å）$-$ $I$ 波段颜色比使用缺乏MIRI数据的测光得到的颜色平均要蓝0.4个星等。 因此，这些星系具有更低的（恒星）质量-光度比。 MIRI的数据使这些星系的恒星质量在$4<z<6$时降低了$\langle \Delta\log M_\ast\rangle=0.25$个dex（即1.8倍），在$6<z<9$时降低了0.37个dex（即2.3倍）。 这还将恒星形成率（SFR）降低了$\langle \Delta\log\mathrm{SFR} \rangle=0.14$在$4<z<6$和$6<z<9$处 0.27 dex。MIRI 数据还改进了对早期恒星形成过程中允许形成的恒星质量的限制。我们使用一个包含“爆发”（在$z_f=100$处）和缓慢变化的（“延迟-$\tau$”）模型的恒星形成历史来模拟这一点。 MIRI 数据使$4<z< 6$处的允许恒星质量减少了 0.6 dex，在$6<z<9$处减少了$\approx$1 dex。 将这些结果应用于全局，这使得早期宇宙（$z\approx9$）的宇宙恒星质量密度减少了十倍。 因此，观测框架下的$\gtrsim$1$\mu$米对于限制高红移星系中的恒星质量累积至关重要。