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CO observations towards H I-rich Ultradiffuse Galaxies

Wang, Junzhi and Yang, Kai and Zhang, Zhi-Yu and Fang, Min and Shi, Yong and Liu, Shu and Li, Juan and Li, Fei (2020) CO observations towards H I-rich Ultradiffuse Galaxies. Monthly Notices of the Royal Astronomical Society: Letters, 499 (1). L26-L30. ISSN 1745-3925. doi:10.1093/mnrasl/slaa150.

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We present CO observations towards a sample of six H I-rich Ultradiffuse galaxies (UDGs) as well as one UDG (VLSB-A) in the Virgo Cluster with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope. CO J = 1–0 is marginally detected at 4σ level in AGC 122966, as the first detection of CO emission in UDGs. We estimate upper limits of molecular mass in other galaxies from the non-detection of CO lines. These upper limits and the marginal CO detection in AGC 122966 indicate low mass ratios between molecular and atomic gas masses. With the star formation efficiency derived from the molecular gas, we suggest that the inefficiency of star formation in such H I-rich UDGs is likely caused by the low efficiency in converting molecules from atomic gas, instead of low efficiency in forming stars from molecular gas.

Item Type:Article
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URLURL TypeDescription Paper ItemData
Yang, Kai0000-0002-5983-198X
Zhang, Zhi-Yu0000-0002-7299-2876
Fang, Min0000-0001-8060-1321
Shi, Yong0000-0002-8614-6275
Li, Juan0000-0003-3520-6191
Alternate Title:CO observations toward HI-rich Ultra Diffuse Galaxies
Additional Information:© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 August 21. Received 2020 August 20; in original form 2020 May. Published: 27 August 2020. We thank the referee, Dr U. Lisenfeld, for helpful suggestions to improve the manuscript. This work is supported by National Key Basic Research and Development Program of China (grant no. 2017YFA0402704) and the National Natural Science Foundation of China grant 11590783 and U1731237. This study is based on observations carried out under project number 068-15 with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This work is also benefited from the International Space Science Institute (ISSI/ISSI-BJ) in Bern and Beijing, thanks to the funding of the team ‘Chemical abundances in the ISM: the litmus test of stellar IMF variations in galaxies across cosmic time’ (Principal Investigator DR and ZYZ). JW thanks Dr Yu Lu for helpful discussion about UDGs. Data Availability: The original CO data observed with IRAM 30-m telescope can be accessed by IRAM archive system at, while optical images can be obtained from PTF and ZTF archive systems. If anyone is interested in the reduced data presented in this paper, please contact Junzhi Wang at
Funding AgencyGrant Number
National Key Basic Research and Development Program of China2017YFA0402704
National Natural Science Foundation of China11590783
National Natural Science Foundation of ChinaU1731237
Institut National des Sciences de l'Univers (INSU)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Instituto Geográfico Naciona; (IGN)UNSPECIFIED
International Space Science Institute (ISSI)UNSPECIFIED
Subject Keywords:galaxies: ISM–galaxies: star formation
Issue or Number:1
Record Number:CaltechAUTHORS:20201130-105703382
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Official Citation:Junzhi Wang, Kai Yang, Zhi-Yu Zhang, Min Fang, Yong Shi, Shu Liu, Juan Li, Fei Li, CO observations towards H I-rich Ultradiffuse Galaxies, Monthly Notices of the Royal Astronomical Society: Letters, Volume 499, Issue 1, November 2020, Pages L26–L30,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106844
Deposited By: Tony Diaz
Deposited On:02 Dec 2020 20:16
Last Modified:16 Nov 2021 18:57

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