利用詹姆斯·韦布空间望远镜研究高红移星系中的星云连续谱
Nebular continuum in high-redshift galaxies with JWST
AI总结：
利用JWST研究高红移星系星云连续谱，选54个星系拟合光谱，发现Hα和Hβ等效宽度是X$_{\text{neb}}$合适示踪剂，确认X$_{\text{neb}}$ = 8%阈值，揭示光学光谱拟合时考虑两者发射对获可靠属性估计的重要性。
AI中文摘要：
研究表明，在进行光学光谱拟合时，同时考虑恒星和星云连续谱发射的相关性主要局限于本地宇宙中的星系。詹姆斯·韦布空间望远镜提供的高质量光谱，为在更年轻的宇宙中开展这些研究开辟了可能性。我们旨在估计高红移恒星形成星系的星云连续谱贡献（X$_{\text{neb}}$），探索其与常见示踪剂和星系属性的关系，并检验先前确定的显著星云贡献阈值（X$_{\text{neb}}$ = 8%）。我们从詹姆斯·韦布空间望远镜的黎明档案中选择了54个符合光谱拟合质量标准的恒星形成星系样本，使用种群合成代码FADO进行拟合。所选星系覆盖1.7 < z < 3.9范围，我们拟合它们的静止帧光学光谱，以估计恒星和星云连续谱发射，以及物理和演化属性。我们发现，在高红移时，H$\alpha$和H$\beta$等效宽度仍然是X$_{\text{neb}}$的合适示踪剂。我们还确认了X$_{\text{neb}}$ = 8%的阈值，高于该阈值忽略星云连续谱会显著影响光谱建模。高于此阈值的星系通常质量较小、更年轻，具有更高的恒星形成活动和更低的尘埃消光。此外，这些星系的光度和质量由年龄小于20 Myr的恒星群体主导，尽管由于光度影响，它们的质量贡献可能被高估。考虑到詹姆斯·韦布空间望远镜和未来设施（如MOONS）在宇宙正午时期星系光谱数据的不断增加，这项工作揭示了在进行光学光谱拟合时正确考虑恒星和星云连续谱发射对于获得可靠的恒星群体和物理属性估计的重要性。
英文摘要：
Studying the relevance of accounting for both stellar and nebular continuum emission when performing optical spectral fitting has been mainly limited to galaxies in the local Universe. The high-quality spectroscopy provided by JWST is now opening the possibility of carrying out these studies in the younger Universe. We aim to estimate the nebular continuum contribution (X$_{\text{neb}}$) of high-redshift star-forming (SF) galaxies, explore its relation to common tracers and galaxy properties, and test the previously established threshold for significant nebular contribution (X$_{\text{neb}}$ $=$ 8%). We select a sample of 54 SF galaxies from the DAWN JWST Archive meeting quality criteria required for spectral fitting with the population synthesis code FADO. The selected galaxies cover the 1.7 $<$ $z$ $<$ 3.9 range and we fit their rest-frame optical spectra to estimate the stellar and nebular continuum emission, plus the physical and evolutionary properties. We show that the H$α$ and H$β$ equivalent widths remain suitable tracers of X$_{\text{neb}}$ at high redshift. We also confirm the X$_{\text{neb}}$ $=$ 8% threshold, above which neglecting the nebular continuum can significantly bias spectral modelling. Galaxies above this threshold are generally less massive, younger, exhibit higher SF activity and lower dust extinction relative to those below it. Moreover, these galaxies are light and mass dominated by stellar populations younger than 20 Myr, although their mass contribution is likely overestimated due to the outshining effect. Considering the growing amount of galaxy spectroscopic data at Cosmic Noon from JWST and future facilities, such as MOONS, this work reveals the importance of properly accounting for both stellar and nebular continuum emission when performing optical spectral fitting to obtain reliable stellar population and physical properties estimates.
