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Molecular clouds in a Milky Way progenitor at z = 1

Published online by Cambridge University Press:  04 June 2020

Miroslava Dessauges-Zavadsky
Affiliation:
Observatoire de Genève, Université de Genève, Versoix, Switzerland email: [email protected]
Johan Richard
Affiliation:
Université Lyon, Université Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, Saint-Genis-Laval, France
Françoise Combes
Affiliation:
LERMA, Observatoire de Paris, PSL Research Université, CNRS, Sorbonne Université, UPMC Paris, France Collège de France, Paris, France
Daniel Schaerer
Affiliation:
Observatoire de Genève, Université de Genève, Versoix, Switzerland email: [email protected] CNRS, IRAP, Toulouse, France
Wiphu Rujopakarn
Affiliation:
Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand National Astronomical Research Institute of Thailand (Public Organization), Chiang Mai, Thailand Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, University of Tokyo, Kashiwa, Japan
Lucio Mayer
Affiliation:
Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Zurich, Switzerland Physik-Institut, University of Zurich, Zurich, Switzerland
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Abstract

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Thanks to the remarkable ALMA capabilities and the unique configuration of the Cosmic Snake galaxy behind a massive galaxy cluster, we could resolve molecular clouds down to 30 pc linear physical scales in a typical Milky Way progenitor at z = 1.036, through CO(4–3) observations performed at the ∼ 0.2″ angular resolution. We identified 17 individual giant molecular clouds. These high-redshift molecular clouds are clearly different from their local analogues, with 10–100 times higher masses, densities, and internal turbulence. They are offset from the Larson scaling relations. We argue that the molecular cloud physical properties are dependent on the ambient interstellar conditions particular to the host galaxy. We find these high-redshift clouds in virial equilibrium, and derive, for the first time, the CO-to-H2 conversion factor from the kinematics of independent molecular clouds at z = 1. The measured large clouds gas masses demonstrate the existence of parent gas clouds with masses high enough to allow the in-situ formation of similarly massive stellar clumps seen in the Cosmic Snake galaxy in comparable numbers. Our results support the formation of molecular clouds by fragmentation of turbulent galactic gas disks, which then become the stellar clumps observed in distant galaxies.

Type
Contributed Papers
Copyright
© International Astronomical Union 2020

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