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arXiv · 2211.00793

ALMA Observations for CO Emission from Luminous Lyman-break Galaxies at $z=6.0293$-$6.2037$

Yoshiaki Ono·Seiji Fujimoto·Yuichi Harikane·Masami Ouchi·Livia Vallini·Andrea Ferrara·Takatoshi Shibuya·Andrea Pallottini·Akio K. Inoue·Masatoshi Imanishi·Kazuhiro Shimasaku·Takuya Hashimoto·Chien-Hsiu Lee·Yuma Sugahara·Yoichi Tamura·Kotaro Kohno·Malte Schramm
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Abstract

We present our new Atacama Large Millimeter/submillimeter Array (ALMA) observations targeting CO(6-5) emission from three luminous Lyman break galaxies (LBGs) at $z_{\rm spec} = 6.0293$-$6.2037$ found in the Subaru/Hyper Suprime-Cam survey, whose [OIII]$88\mu$m and [CII]$158\mu$m emission have been detected with ALMA. We find a marginal detection of the CO(6-5) line from one of our LBGs, J0235-0532, at the $\simeq 4 \sigma$ significance level and obtain upper limits for the other two LBGs, J1211-0118 and J0217-0208. Our $z=6$ luminous LBGs are consistent with the previously found correlation between the CO luminosity and the infrared luminosity. The unique ensemble of the multiple far-infrared emission lines and underlying continuum fed to a photodissociation region model reveal that J0235-0532 has a relatively high hydrogen nucleus density that is comparable to those of low-$z$ (U)LIRGs, quasars, and Galactic star-forming regions with high $n_{\rm H}$ values, while the other two LBGs have lower $n_{\rm H}$ consistent with local star-forming galaxies. By carefully taking account of various uncertainties, we obtain total gas mass and gas surface density constraints from their CO luminosity measurements. We find that J0235-0532 locates below the Kennicutt-Schmidt (KS) relation, comparable to the previously CO(2-1) detected $z=5.7$ LBG, HZ10. Combined with previous results for dusty starbursts at similar redshifts, the KS relation at $z=5$-$6$ is on average consistent with the local one.

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Yoshiaki Ono, Seiji Fujimoto, Yuichi Harikane, Masami Ouchi, Livia Vallini, Andrea Ferrara, Takatoshi Shibuya, Andrea Pallottini, Akio K. Inoue, Masatoshi Imanishi, Kazuhiro Shimasaku, Takuya Hashimoto, Chien-Hsiu Lee, Yuma Sugahara, Yoichi Tamura, Kotaro Kohno, Malte Schramm. 2022-11-02. ALMA Observations for CO Emission from Luminous Lyman-break Galaxies at $z=6.0293$-$6.2037$. https://doi.org/10.3847/1538-4357%2Fac9ea6

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