Identifying reionization-epoch galaxies with extreme levels of Lyman continuum leakage in James Webb Space Telescope surveys
Identifying reionization-epoch galaxies with extreme levels of Lyman continuum leakage in James Webb Space Telescope surveys
复制标题
在詹姆斯·韦伯太空望远镜巡天中识别具有极端莱曼连续泄漏水平的再电离时代星系
DOI：
10.1093/mnras/stz3416
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发表时间：
2019
影响因子：
4.8
通讯作者：
Ruben Cubo
中科院分区：
文献类型：
--
作者：
S. Giri;E. Zackrisson;C. Binggeli;K. Pelckmans;Ruben Cubo
詹姆斯·韦伯太空望远镜 (JWST) NIRSpec 仪器将允许在再电离 (EoR) 时代对星系进行静止框架紫外/光学光谱分析。一些星系可能会表现出氢电离光子大量泄漏到星系间介质中，从而导致微弱的星云发射线。我们提出了一个机器学习框架，用于根据透镜场中 EoR 星系的潜在 NIRSpec 观测所预期的数据质量来识别非常高的氢电离光子从星系逃逸的情况。我们在红移 z = 6–10 的星系的 JWST/NIRSpec 数据模拟样本上训练我们的算法。为了使样本更加真实，我们将基于宇宙学星系模拟的合成星系光谱与与 z ≳ 6 天体相关的观测噪声结合起来，这些天体的亮度类似于星系团 Abell-2744 和 MACS-J0416 的前沿场观测中发现的 EoR 候选星系。我们发现，在分辨率 R = 100 下进行 24 小时 (1.5 小时) JWST/NIRSpec 曝光时，可以检索比 mAB,1500 ≈ 27 mag 亮的星系的电离逃逸分数 (fesc)，平均绝对误差 Δfesc ≈ 0.09(0.12)。对于 24 小时曝光时间，甚至更暗的星系 (mAB,1500 < 28.5 mag) 可以用 Δfesc ≈ 0.14 进行处理。该框架同时估计这些星系的红移，在 24 小时（mAB，1500 < 28.5 mag）和 1.5 小时（mAB，1500 < 27 mag）曝光时间下，相对误差小于 0.03。我们还考虑了只有一小部分星系达到高 fesc 的情况，并提出了检测数据集中高 fesc 星系子群所需的条件。
The James Webb Space Telescope (JWST) NIRSpec instrument will allow rest-frame ultraviolet/optical spectroscopy of galaxies in the epoch of reionization (EoR). Some galaxies may exhibit significant leakage of hydrogen-ionizing photons into the intergalactic medium, resulting in faint nebular emission lines. We present a machine learning framework for identifying cases of very high hydrogen-ionizing photon escape from galaxies based on the data quality expected from potential NIRSpec observations of EoR galaxies in lensed fields. We train our algorithm on mock samples of JWST/NIRSpec data for galaxies at redshifts z = 6–10. To make the samples more realistic, we combine synthetic galaxy spectra based on cosmological galaxy simulations with observational noise relevant for z ≳ 6 objects of a brightness similar to EoR galaxy candidates uncovered in Frontier Fields observations of galaxy cluster Abell-2744 and MACS-J0416. We find that ionizing escape fractions (fesc) of galaxies brighter than mAB,1500 ≈ 27 mag may be retrieved with mean absolute error Δfesc ≈ 0.09(0.12) for 24 h (1.5 h) JWST/NIRSpec exposures at resolution R = 100. For 24 h exposure time, even fainter galaxies (mAB,1500 < 28.5 mag) can be processed with Δfesc ≈ 0.14. This framework simultaneously estimates the redshift of these galaxies with a relative error less than 0.03 for both 24 (mAB,1500 < 28.5 mag) and 1.5 h (mAB,1500 < 27 mag) exposure times. We also consider scenarios where just a minor fraction of galaxies attain high fesc and present the conditions required for detecting a subpopulation of high-fesc galaxies within the data set.