大爆炸后7亿年后，最近淬火的银河系

　　在这项工作中介绍的Jades-GS-Z7-01-QU的NIRSPEC49 Prism/R100和Graist/R1000光谱是作为我们的Jades GTO计划（PI：N。Lützgendorf，ID：1210：1210）的一部分获得的一部分配置棱镜/透明，覆盖0.6μm和5.3μm之间的波长范围，并为光谱提供了依赖波长的光谱分辨率为r≈30–330。Jades-GS-Z7-01-QU的R100频谱如图1所示。 　　中分辨率的R1000观测值，光谱分辨率为r≈500–1,340，使用了分散器/滤波器构型，并将其暴露于14 h，7 h和7 h。A zoom-in on the R1000 spectrum (into the region with spectral lines best tracing star-formation activity) is shown in Extended Data Fig. 1. Finally, high-resolution R2700 observations used and were exposed for 7 h (like the R1000 spectrum, the R2700 spectrum of JADES-GS-z7-01-QU contains no detections, hence is not shown). 　　该程序在三个抖动点上观察到了总共253个星系，在三个点中的每个点中都观察到Jades-GS-Z7-01-qu。每个抖动指向都有不同的微骨阵列（MSA）构型，以将光谱放置在检测器上的不同位置，以减少检测器间隙的影响，减轻检测器伪像并改善高优势目标的信号效率比，同时增加观察到的靶标的密度。在每个单独的抖动指向内，望远镜执行了三个NOD模式（通过将望远镜的长度稍微重新定向一个微毛，保持相同的MSA配置）。在三个点点数中的每个点中，每个目标都打开了三个微毛，目标是中央快门的目标。每个三点点头在8,403 s内执行。点头模式已在棱镜/清除配置中重复四次，在G140M/F070LP组合中进行了两次，一次在G235M/F170LP组合中，一次是G395M/F290LP组合。这导致了R100的Jades-GS-Z7-01-28小时的总暴露时间，在G140M中为14 h，在G235M，G395M和G395H中为7小时。 　　使用NIRSPEC GTO团队开发的定制管道提取了磁通量的光谱，该管道建立在公共可用的ESA NIRSPEC科学运营团队（SOT）Pipeline50上。自定义管道的详细描述将在即将发表的技术论文（Carniani等人的准备中）中介绍，并在参考文献中找到更多信息。51。我们在这里总结了公开管道的主要步骤和差异。对于每次曝光，我们提取每个像素的计数速率，删除宇宙射线并标记饱和度。2D频谱是根据三个节点模式的其他两个暴露量减去背景的。考虑到波长依赖性吞吐量，单个2D光谱是平坦的，并经过照明校正。然后应用波长和通量校准，2D光谱的每个像素具有相关的波长和沿快门的位置。考虑到NIRSPEC的相当大的点扩散功能变化，我们应用了依赖波长的途径校正，以解释降低微骨外的通量，从而将目标视为点源。对于棱镜，我们使用了不规则的光谱波长网格，考虑到分辨率（R）作为波长的函数。来自三个点中每个点的三个点点位置的1D光谱由加权平均值组合为单个1D光谱。用Sigma覆盖算法拒绝异常值。提出的1D光谱来自1D单个光谱的组合，不是从提出的合并2D光谱中提取的。 　　JWST/NIRCAM F444W-F200W-F090W RGB（红色绿色）的Jades-gs-Z7-01-Qu的颜色图像来自我们的Jades程序（PI：Daniel J. Eisenstein，ID：1180），由每个过滤器中的Mosaics在evavellentts evellengths evellengts cutounts of beangeents of Plactends Evellengts cute feleds evellengts cute feleds evellengts cutefergents evellengtsλ≈5– 5 usef。 　　对于Jades-GS-Z7-01-QU的分光光度模型，我们使用了JADES和JEMS52 NIRCAM53,54调查的光度法。特别是，建模包括具有以下过滤器的深红色nircam观测值：F090W，F115W，F150W，F182M，F200W，F210M，F277W，F277W，F335M，F3356W，F356W，F410M，F430M，F430M，F430M，F444W，F444W，F44460M和F460M和F48880M和F4880M和F4880M和F4880M和F4880M和F4880M和F4880M和F4880M和F4880M。JADES光学减少管道利用了JWST校准管道（JWSTCP，v1.9.2）具有CRDS PMAP上下文1039。将原始图像转换为计数率图像，使用JWSTCP阶段1，为此使用了检测器级校正和“雪球”。然后使用JWSTCP阶段2对计数速率图像进行平坦的固定并使用定制方法对磁通量进行校准。最后，使用管道的第3阶段创建了马赛克。有关JADES光度计数据减少管道的更多详细信息，请参见参考文献。10。Nat。astron。7，611–621（2023）。“ href =” https://www.nature.com/articles/s41586-024-024-07227-07227-0#ref-cr55“ id =” ref-link-section-ref-link-section-d30045713e3120“> 55,56。 　　为了获得Jades-gs-Z7-01-Qu的形态学参数，我们将Nircam光度法与武器拟合（Johnson等人，在准备中）。武力模型的星系和子结构（例如，团块或混合伴侣）作为几个sérsic曲线，仪器点卷积，通过仪器点扩散作为高斯人的混合物，通过向前模型中的所有曝光和过滤器中的光分布并采样了通过马尔可夫链Monte Carlo的所有参数分布的所有滤镜，并采样了所有参数的后验概率分布。有关多组分建模过程的更多详细信息，请参见参考文献。56。JADES-GS-Z7-01-QU以紧凑的，盘状的星系为单位（半光线半径RE = 36±1 MAS 0.2 kpc 0.2 kpc 0.04 arcsec，sérsicindex n = 0.95±0.03;扩展数据图2）。这些图像还显示出东方的独特，淡淡的源0.13 Arcsec。该次级源不能在光谱中脱串，但是我们使用武器获得了分解的光度法。次级源对总通量的贡献范围从最多27％（在F115W频段）到17％（在F444W频段中），因此其SED比主要来源的SED要蓝很多。它的光度红移Z = 7.50±0.13（1σ）与主要来源的光谱红移一致。在Z = 7.3的红移时，此次级来源将位于Jades-GS-Z7-01-QU;它将其解释为团块或卫星尚不清楚。为了尝试从主要来源的光谱中取出其贡献，我们从中央三个像素（0.3 arcsec）中提取了NIRSPEC 2-D光谱的频谱；使用此频谱不会改变我们结果的解释，即Jades-GS-Z7-01-Qu仍被淬灭。 　　正如主要文本中讨论的那样，由于没有其他星系驻留在附近，因此排除了Jades-GS-Z7-01-Qu的环境淬火。可以通过在我们公开的网站上的Jades Nircam成像进行验证，更具体地说是交互式工具fitsMap：https：//jades.idies.jhu.edu.edu/public/?ra=53.1554497&dec=-27.8018917&zoom = 9 at Coordinates ra = 53.1551和dec.53.1551 and coordinate and coordinate and coordinate and coordinate and coordinate and coordin.1551 and = 53.1551＆dechore = 53.151 and = 53.151和dec.15151 and = 53.1551 and = 53.151。= −27.8018。 　　使用单个恒星种群（SSP）模板库中获得的合成C3K模型Ambility59与Isochrones600和Solar Abund ancemants 60和SOLAR ABUNDANCES，使用单个恒星种群（SSP）模板光谱，使用χ2-Minimization惩罚的像素拟合代码PPXF（参考文献57,58）进行了图1中恒星连续体的红色模型拟合。SSP光谱跨越了整个2D对数网格，为62年龄，10个金属度，从AGESSP = 106.0岁到109.2岁（慷慨大于Z = 7.3时的宇宙年龄）和Log10（Z/Z）SSP = -2.5至0.5。由于R100频谱的低分辨率，我们将恒星速度分散液固定在其病毒估计下。为了考虑灰尘的变红，拟合的SSP在参考文献中以多重耦合到尘埃衰减曲线。61。推断图2a所示的恒星种群权重网格，参考文献。62，我们首先卷动SSP模板以匹配棱镜光谱的波长依赖性光谱分辨率。然后，为避免数值问题，光谱和模板都被每个光谱像素的中值磁通重新归一致。然后，我们使用PPXF运行初始拟合，并在频谱中运行σ-CLIP离群体。最后，我们对最初的PPXF最佳拟合度进行了基于残差的自举，而没有正则化57,58，超过1,000次迭代。将所推论的自举的SSP网格平均以恢复非参数SFH，与图2A所示的频谱的固有噪声一致。 　　我们推断出该星系中恒星的灰尘衰减，该星系为AV = 0.4±0.1。应该注意的是，PPXF拟合中的灰尘的存在主要由紫外斜率驱动。SSP模板中不包括LYα滴的复杂物理。掩盖频谱的这一部分恢复了几乎无尘的拟合度，而较旧的和金属富的恒星种群将使Jades-gs-Z7-01-que更加淬火。如主文本中所述，我们推断出使用PPXF的Log10（z/z）≈ -2的平均恒星金属度极低。应当指出的是，主要的重建恒星种群位于log10（z/z）≈ -2.5，在合成光谱的可用网格的边界处。这表明将来可能需要较低金属性的模型SSP光谱，以准确地对高红移的星系中的星系中的恒星种群进行建模。但是，我们注意到，由于棱镜的分辨率低，金属性测量值不确定。我们推断出银河系中最古老的恒星人群（即表明恒星形成的开始）为150 Myr旧，而最小的年龄为50 Myr，导致星系的恒星形成极短，在银河系的形成和淬火之间。 　　我们使用星系的贝叶斯分析进行物理推理和参数估计（风笛）代码63，以同时拟合NIRSPEC PRISM测量和NIRCAM光度法。以下参考。64，我们使用了更新的BC03恒星人口型号65,66与Stellar Miles Library 67和更新的Stellar Evolution Tracks68,69。对于提出的风笛拟合，我们假设两个常数SFH的垃圾箱，一个在过去的10个MYR中固定垃圾箱，一个固定的垃圾桶，一个可变的bin，范围超过10 Myr（最小年龄在10 Myr之间，在10 Myr和0.5 Gyr之间，最大年龄在11 Myr和Universe的年龄之间）。我们改变了在0到1015 m之间形成的总恒星质量，并在0.01 z和1.5 z之间变化，可变SFH箱的恒星金属性（10-myr bin具有0.2 z的10 myr bin，以匹配可变SFH箱的推断金属性）。用具有电离参数的Cloudy70模型的网格对Nebular发射进行自兼而有的建模（-3< log10U < −0.5) as a free parameter. We included a flexible dust attenuation prescription71 with visual extinction and power-law slope freely varying (0 < AV < 7, 0.4 < n < 1.5) while fixing the fraction of attenuation from stellar birth clouds to 60% (the remaining fraction arising in the diffuse ISM; ref. 72). A first-order correction polynomial73 is fitted to the spectroscopic data to account for aperture and flux calibration effects. The spectrophotometric fit and the corresponding corner plot are shown in Extended Data Fig. 3. We find that nearly no wavelength-dependant correction is necessary at the blue end of the spectrum, whereas at the red end, a correction of 15% is applied. Crucially, we find a very low SFR (consistent with 0) in the past 10 Myr for JADES-GS-z7-01-QU, noting that other tested SFH parametrizations, namely the double-power-law SFH described in ref. 74 and a single-bin constant SFH with flexible beginning and end of star formation, return consistent results and most crucially agree that the galaxy is quenched. We infer that the oldest stellar population is 40 Myr old, which is equivalent to a formation redshift of z = 7.6. The galaxy has been quenched for 10 Myr, resulting in a short duration of star formation of 20 Myr from the formation of the galaxy to its quenching. 　　We use the Bayesian analysis tool BEAGLE (ref. 66) to fit to the R100/prism spectrum of JADES-GS-z7-01-QU. The BEAGLE code incorporates a consistent modelling of stellar radiation and its transfer through the interstellar and intergalactic media. We model the SFH as an initial delayed exponential with maximum stellar age, tform (years), and location of the peak of star formation as free parameters. To disentangle the current SFR from the integrated property of total stellar mass, we allow for the most recent episode of star formation to be modelled as a constant with free parameters SFR (M yr−1) and duration, tquench (years) (which can vary between 107 and 108 years). The nebular emission is characterized by the interstellar metallicity, the ionization parameter, the mass fraction of interstellar metals locked within dust grains and, crucially, fesc (which can vary between 0 and 1). Dust attenuation follows the two-component prescription of ref. 71, in which we fit for the total effective V-band attenuation optical depth (fixing the ratio of V-band ISM attenuation to the V-band ISM + birth cloud attenuation to 0.4). We also fit for stellar metallicity, stellar mass formed and redshift, totalling 12 free parameters. A list of the free parameters and the adopted priors is presented in Extended Data Table 1. 　　The corner plot in Extended Data Fig. 4 shows the BEAGLE posterior probability distributions of the BEAGLE fit. The 2D (off-diagonal) and 1D (along the main diagonal) subplots show the posterior distributions on stellar mass M, metallicity Z, SFR, maximum age of stars tform, minimum age of stars tquench, redshift z, effective dust attenuation optical depth in the V-band AV and the escape fraction of ionizing photons fesc. The dark, medium and light blue contours show the extents of the 1σ, 2σ and 3σ credible regions. 　　BEAGLE gives a current SFR of less than 10−1.5 M yr−1, a formation time of less than 160 Myr before observation and a quenching time of roughly 15 Myr before observation. 　　We also note that BEAGLE, as for the other three codes, requires some degree of dust attenuation, which suggests that some cold gas is still present, which—in turn—is incompatible with fesc ≈ 1. 　　We use the Bayesian SED fitting code Prospector75 to model the spectrophotometric data of JADES-GS-z7-01-QU. The posterior corner plot for several key parameters from Prospector is shown in Extended Data Fig. 5. The code uses a flexible spectroscopic calibration model, combined with forward modelling of spectra and photometry, to infer physical properties. Following the setup in ref. 76, we include a flexible SFH (ten bins with the bursty continuity prior), a flexible attenuation law (diffuse dust optical depth with a power-law modifier to shape the attenuation curve of the diffuse dust in ref. 61) and fit for the stellar metallicity. Notably, Prospector infers a low-dust attenuation with with a rather steep attenuation law . This is consistent with the idea that the galaxy has a low gas content and the low SFR in the past 30 Myr before observation. Prospector infers that the oldest stellar population (as defined by the lookback time when the first 10% of the stellar mass formed) has an age of about 100 Myr, which means a nominal formation redshift of z = 8.8. The SFR increases markedly approximately 80 Myr before observation. After this final burst, lasting around 50 Myr, the galaxy quenched on a short timescale. 　　We have also experimented with the standard continuity prior77, which weights against sharp transition in the SFH. The overall shape of the SFH is the same, indicating that the data strongly prefer a decreasing SFH in the past roughly 50 Myr. Quantitatively, the recent SFR (averaged over the past 10 Myr) increases with this prior to , which is still consistent with being quenched and within the uncertainties of the fiducial value obtained with the bursty continuity prior. The quenching time is slightly more recent , but consistent within the uncertainties quoted in Table 1. 　　It should be noted that the complete absence of nebular lines always allows, by construction, a solution with fesc ≈ 1 (regardless of whether the galaxy has been recently star forming or quiescent)—the question is whether this solution is accompanied by the production of ionizing photons associated with continuing star formation. 　　The fiducial BEAGLE posterior distribution does not highlight a solution with high fesc and very recent star formation26,29,78. By contrast, although fesc is unconstrained, even a value approaching unity indicates a low SFR < 0.1 M yr−1 at the 3σ level (fifth subplot from the left at the bottom of Extended Data Fig. 4). 　　To assess the very recently star-forming and high-fesc scenario quantitatively, we use BEAGLE to compare two SED models. The model already described (see the ‘BEAGLE’ section) formally allows a star-forming solution with high fesc. The alternative model has a simplified SFH consisting of a constant SFR; in this way, low-SFR solutions are effectively removed by the constraint to form sufficient stellar mass of the appropriate age to reproduce the observed spectrum. This alternative model gives and , which is a much higher SFR than the alternative solution. To select the preferred model, we use the Bayes ratio, that is, the ratio between the evidence of the models. The log difference between the evidences, that is, the Bayes factor, is ln(K) = 4.1 ± 0.3; according to Jeffreys’ criterion79, this is strong evidence for the quenched solution and we adopt it as our fiducial model. 　　As an extra test, we assumed a model with the same setup as the fiducial run, but forcing the escape fraction to fesc >0.9。我们发现结果等于基准运行，并且银河系仍然淬火。 　　为了估计Hβ和[O III]λ5008上的通量上限，我们将三个像素的形式差异列入。因为我们使用Lick Definition80中的频段，但由于光谱分辨率而没有任何进一步的校正。 　　我们从Hβ发射线通量的3σ上限F（Hβ）<6.1×10-20-20 ERG cm-2 s-1得出了SFR上极限。为了纠正这种通量以进行尘埃衰减，我们假设银河系衰减法律，它至少适合到Z = 2.5（参考文献82,83）。鉴于未检测到Hβ，我们无法测量Balmer降低。因此，我们从比格（Beagle）（所有型号之间的最高值）和高档该值推出的连续体AV = 0.64，从0.64中得出了Nebular AV，该值是从局部galaxies84推断的中位连续性与nebular av率（从与Jades-gs-Z7-01-Qu的恒星质量相当）。假设Planck18 Cosmology85，将通量转换为光度。为了将经Hβ衰减的亮度转换为SFR，我们使用转化因子2.1×10-42 m yr-1 erg-1 s，适用于Chabrier的初始质量函数，高质量临界值为100 m，金属性为z = 0.27 z（参考文献83）（请参阅该估算的价值比该估算的值更高。这给出了0.57 m yr -1的SFR。甚至更强的限制来自[O III]λ5008线：我们发现F（[O III]λ5008）<6.5×10-20 ERG S-1 cm-2，与[O III]λ5008/Hβ率的保守假设相结合，在High-Z galaxies15 limem a Bly Implies a Blafties a s 3 s offiles a s 3 limitive in 3 limitive in 3 limitive in 3 limitive ofties a s 3 limitive in 3 limitive off。（SFR = 0.12 m yr -1）。 　　另外，假设中位数（和极端）观察到Balmer减少3.5（5.5）。83，我们将分别获得0.63和2.05 mag的星云AV值。这些分别转化为[O III]λ5008衍生的SFR，分别为0.10和0.34 m yr-1。作为比较，在z = 7.3处的静止的SFR阈值为0.18 m yr -1（从SSFR中的阈值获得的SSFR阈值是0.2/th（z）乘以Beagle恒星质量（参考文献86）的0.2/th（Z）。因此，除了最极端的情况外，Jades-GS-Z7-01-Qu将达到静止的正式阈值。中等分辨率频谱独立确认发射线的缺失（参见扩展数据图1）。