CO Emission of Dust-Rich Broad-Emission-Line Quasars

Subjects: Astronomy submitted time 2024-01-05 Cooperative journals: 《天文学进展》

LIU Feng-yuan, DAI Yu, WU Jing-wen

Abstract： Dust-rich broad-emission-line qusars (DBQs) are in a critical phase in galaxy evolution, whose star-forming potential can be revealed by the molecular gas. We used the IRAM-30m telescope to observe CO emission lines in nine DBQs at 0.5 < z < 3, and detected nine lines at different transitions in eight sources. Five lines are strong detections, and four lines are tentative detections. According to the CO line-width versus line luminosity diagram, seven sources satisfy the unlensed/slightly-lensed relation, while one is likely to be strongly lensed by a factor of about 12. With lensing-corrected infrared luminosities from the literature and SED fitting, we estimate their star formation rates to be approximately 40 ∼ 3 500 M⊙·a −1 , and the gas depletion time to be approximately 20 ∼ 300 Ma. Their star formation efficiency shows no significant difference from other SMGs and QSOs comparing their IR and CO luminosities. We find a negative correlation between AGN relative strength and gas depletion time, which is consistent with the QSO evolutionary model.

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