With the remarkable sensitivity and resolution of JWST in the infrared, measuring rest-optical kinematics of galaxies at z > 5 has become possible for the first time. This study pilots a new method for measuring galaxy dynamics for highly multiplexed, unbiased samples by combining FRESCO NIRCam grism spectroscopy and JADES medium-band imaging. Here we present one of the first JWST kinematic measurements for a galaxy at z > 5. We find a significant velocity gradient, which, if interpreted as rotation, yields V _rot = 305 ± 70 km s⁻¹, and we hence refer to this galaxy as Twister-z5. With a rest-frame optical effective radius of r _e = 2.25 kpc, the high rotation velocity in this galaxy is not due to a compact size, as may be expected in the early Universe, but rather to a high total mass, log(Mdyn/M⊙)=11.2±0.2 . This is a factor of roughly 10× higher than the stellar mass within r _e . We also observe that the radial Hα equivalent width profile and the specific star formation rate map from resolved stellar population modeling are centrally depressed by a factor of ∼1.5 from the center to r _e . Combined with the morphology of the line-emitting gas in comparison to the continuum, this centrally suppressed star formation is consistent with a star-forming disk surrounding a bulge growing inside out. While large, rapidly rotating disks are common to z ∼ 2, the existence of one after only 1 Gyr of cosmic time, shown for the first time in ionized gas, adds to the growing evidence that some galaxies matured earlier than expected in the history of the Universe.

中文翻译：

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使用 FRESCO 的电离气体运动学：z = 5.4 的扩展、大质量、快速旋转的星系


凭借 JWST 在红外范围内非凡的灵敏度和分辨率，首次可以测量 z > 5 处星系的静止光学运动学。本研究试验了一种通过将 FRESCO NIRCam 光谱和 JADES 中带成像相结合来测量高度多路复用、无偏样品的星系动力学的新方法。在这里，我们展示了 z > 5 处星系的首批 JWST 运动学测量之一。我们发现了一个显著的速度梯度，如果将其解释为旋转，则产生 V_rot = 305 ± 70 km s⁻¹，因此我们将这个星系称为 Twister-z5。这个星系的静止系光学有效半径为 r _e = 2.25 kpc，这个星系的高旋转速度并不是由于紧凑的尺寸，就像在早期宇宙中可以预期的那样，而是由于高总质量，log（Mdyn/M⊙）=11.2±0.2。这比 r _e 内的恒星质量高出大约 10× 倍。我们还观察到，来自解析的恒星种群建模的径向 Hα 等效宽度剖面和特定恒星形成速率图从中心到 r _e 的中心抑制了 ∼1.5 的因子。结合线发射气体与连续体相比的形态，这种集中抑制的恒星形成与围绕着由内而外生长的凸起的星形盘一致。虽然 z ∼ 2 共有大型、快速旋转的圆盘，但在宇宙时间仅 1 Gyr 之后就存在一个圆盘，这是第一次在电离气体中出现，这增加了越来越多的证据表明，一些星系的成熟时间比宇宙历史上预期的要早。