Possible Systematic Rotation in the Mature Stellar Population of a \(z=9.1\) Galaxy

• Published in: arXiv.org 2022-05
• Main Authors: Tokuoka, Tsuyoshi, Inoue, Akio K, Hashimoto, Takuya, Ellis, Richard S, Laporte, Nicolas, Sugahara, Yuma, Matsuo, Hiroshi, Tamura, Yoichi, Fudamoto, Yoshinobu, Moriwaki, Kana, Roberts-Borsani, Guido, Shimizu, Ikkoh, Yamanaka, Satoshi, Yoshida, Naoki, Zackrisson, Erik, Zheng, Wei
• Format: Article
• Language: English
• Subjects: Clumps; Dispersion; Emission analysis; Galactic rotation; Galaxy distribution; Gravitation; Radio telescopes; Rotating disks; Spatial resolution; Spectral energy distribution; Stellar mass; Velocity; Velocity gradient
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2205.14378

We present new observations with the Atacama Large Millimeter/submillimeter Array for a gravitationally-lensed galaxy at \(z=9.1\), MACS1149-JD1. [O III] 88-\(\mu\)m emission is detected at 10\(\sigma\) with a spatial resolution of \(\sim0.3\) kpc in the source plane, enabling the most distant morpho-kinematic study of a galaxy. The [O III] emission is distributed smoothly without any resolved clumps and shows a clear velocity gradient with \(\Delta V_{\rm obs}/2\sigma_{\rm tot}=0.84\pm0.23\), where \(\Delta V_{\rm obs}\) is the observed maximum velocity difference and \(\sigma_{\rm tot}\) is the velocity dispersion measured in the spatially-integrated line profile, suggesting a rotating system. Assuming a geometrically thin self-gravitating rotation disk model, we obtain \(V_{\rm rot}/\sigma_V=0.67_{-0.26}^{+0.73}\), where \(V_{\rm rot}\) and \(\sigma_V\) are the rotation velocity and velocity dispersion, respectively, still consistent with rotation. The resulting disk mass of \(0.65_{-0.40}^{+1.37}\times10^{9}\) M\(_\odot\) is consistent with being associated with the stellar mass identified with a 300 Myr-old stellar population independently indicated by a Balmer break in the spectral energy distribution. We conclude that the most of the dynamical mass is associated with the previously-identified mature stellar population that formed at \(z\sim15\).