arXiv subjects

Tsuyoshi Tokuoka

Publications and source records attributed to Tsuyoshi Tokuoka.

3 recordsLinked to original sources

arXiv2023

The 300 pc resolution imaging of a z = 8.31 galaxy: Turbulent ionized gas and potential stellar feedback 600 million years after the Big Bang

We present the results of 300 pc resolution ALMA imaging of the [OIII] 88 $μ$m line and dust continuum emission from a $z = 8.312$ Lyman break galaxy MACS0416_Y1. The velocity-integrated [OIII] emission has three peaks which are likely associated with three young stellar clumps of MACS0416_Y1, while the channel map shows a complicated velocity structure with little indication of a global velocity gradient unlike what was found in [CII] 158 $μ$m at a larger scale, suggesting random bulk motion of ionized gas clouds inside the galaxy. In contrast, dust emission appears as two individual clumps apparently separating or bridging the [OIII]/stellar clumps. The cross correlation coefficient between dust and ultraviolet-related emission (i.e., [OIII] and ultraviolet continuum) is unity on a galactic scale, while it drops at < 1 kpc, suggesting well mixed geometry of multi-phase interstellar media on sub-kpc scales. If the cutoff scale characterizes different stages of star formation, the cutoff scale can be explained by gravitational instability of turbulent gas. We also report on a kpc-scale off-center cavity embedded in the dust continuum image. This could be a superbubble producing galactic-scale outflows, since the energy injection from the 4 Myr starburst suggested by a spectral energy distribution analysis is large enough to push the surrounding media creating a kpc-scale cavity.

astro-ph.GA↗

arXiv2023

Updated measurements of [O III] 88 $μ$m, [C II] 158 $μ$m, and Dust Continuum Emission from a z=7.2 Galaxy

We present updated measurements of the [O III] 88 $μ$m, [C II] 158 $μ$m, and dust continuum emission from a star-forming galaxy at $z=7.212$, SXDF-NB1006-2, by utilizing Atacama Large Millimeter/submillimeter Array (ALMA) archival data sets analysed in previous studies and data sets that have not been analysed before. The follow-up ALMA observations with higher angular resolution and sensitivity reveal a clumpy structure of the [O III] emission on a scale of $0.32-0.85\,\rm{kpc}$. We also combined all the ALMA [O III] ([C II]) data sets and updated the [O III] ([C II]) detection to $5.9σ$ ($3.6σ-4.5σ$). The non-detection of [C II] with data from the REBELS large program implies the incompleteness of spectral-scan surveys using [C II] to detect galaxies with high star formation rates (SFRs) but marginal [C II] emission at high-$z$. The dust continuum at 90 $μ$m and 160 $μ$m remains undetected, indicating little dust content of $<3.9\times10^{6}\,M_\odot\,(3σ)$, and we obtained a more stringent constraint on the total infrared luminosity. We updated the [O III]/[C II] luminosity ratios to $10.2\pm4.7~(6.1\pm3.5$) and $20\pm12~(9.6\pm6.1$) for $4.5σ$ and $3.6σ$ [C II] detections, respectively, where the ratios in the parentheses are corrected for the surface brightness dimming effect on the extended [C II] emission. We also found a strong [C II] deficit ($0.6-1.3$ dex) between SXDF-NB1006-2 and the mean $L_{\rm{[CII]}}-\rm{SFR}$ relation of galaxies at $0<z<9$.

astro-ph.GA↗

arXiv2022

Possible Systematic Rotation in the Mature Stellar Population of a $z=9.1$ Galaxy

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-$μ$m emission is detected at 10$σ$ 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 $ΔV_{\rm obs}/2σ_{\rm tot}=0.84\pm0.23$, where $ΔV_{\rm obs}$ is the observed maximum velocity difference and $σ_{\rm tot}$ 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 $V_{\rm rot}/σ_V=0.67_{-0.26}^{+0.73}$, where $V_{\rm rot}$ and $σ_V$ 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 $z\sim15$.

astro-ph.GA↗