Detection of the [O I] 63 μm emission line from the z = 6.04 quasar J2054-0005
Ishii, Nozomi, Hashimoto, Takuya, Ferkinhoff, Carl, Rybak, Matus, Inoue, Akio K., Michiyama, Tomonari, Donevski, Darko, Fujimoto, Seiji, Salak, Dragan, Kuno, Nario, Matsuo, Hiroshi, Mawatari, Ken, Tamura, Yoichi, Izumi, Takuma, Nagao, Tohru, Nakazato, Yurina, Osone, Wataru, Sugahara, Yuma, Usui, Mitsutaka, Wakasugi, Koki, Yajima, Hidenobu, Bakx, Tom J.~L.~C., Fudamoto, Yoshinobu, Meyer, Romain A., Walter, Fabian, & Yoshida, Naoki
要旨
We report the highest-redshift detection of [O I] 63 μm from a luminous quasar, J2054-0005, at z = 6.04 based on the Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 9 observations. The [O I] 63 μm line luminosity is (4.51.5) × 109L⊙, corresponding to the [O I] 63 μm-to-far- infrared luminosity ratio of ≈6.7 ×10-4, which is consistent with the value obtained in the local Universe. Remarkably, [O I] 63 μm is as bright as [C II] 158 μm, resulting in the [O I]-to-[C II] line luminosity ratio of 1.30.5. Based on a careful comparison of the luminosity ratios of [O I] 63 μm, [C II] 158 μm, and dust continuum emission to models of photodissociation regions, we find that J2054-0005 has a gas density log(nH∕cm-3) = 3.70.3 and an incident far-ultraviolet radiation field of log(G∕G0) = 3.00.1, showing that [O I] 63 μm serves as an important coolant of the dense and warm gas in J2054-0005. A close examination of the [O I] and [C II] line profiles suggests that the [O I] line may be partially self- absorbed; however, deeper observations are needed to verify this conclusion. Regardless, the gas density and incident radiation field are in broad agreement with the values obtained in nearby star-forming galaxies and objects with [O I] 63 μm observations at z = 1-3 with the Herschel Space Observatory. These results demonstrate the power of ALMA high-frequency observations targeting [O I] 63 μm to examine the properties of photodissociation regions in high-redshift galaxies.
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