Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12666/324
Title: Molecular clouds in the Cosmic Snake normal star-forming galaxy 8 billion years ago
Authors: Dessauges Zavadsky, M.
Richard, J.
Combes, F.
Schaerer, D.
Rujopakarn, W.
Mayer, L.
Cava, A.
Boone, F.
Egami, E.
Kneib, J. P.
Pérez González, P. G.
Pfenniger, D.
Rawle, T. D.
Teyssier, R.
Van der Werf, P. P.
Issue Date: 16-Sep-2019
Publisher: Nature Research Journals
DOI: 10.1038/s41550-019-0874-0
Published version: https://www.nature.com/articles/s41550-019-0874-0
Citation: Nature Astronomy 3(12): 1115-1121(2019)
Abstract: The cold molecular gas in contemporary galaxies is structured in discrete cloud complexes. These giant molecular clouds (GMCs), with 10(4)-10(7) solar masses (M-circle dot) and radii of 5-100 parsecs, are the seeds of star formation(1). Highlighting the molecular gas structure at such small scales in distant galaxies is observationally challenging. Only a handful of molecular clouds were reported in two extreme submillimetre galaxies at high redshift(2-4). Here we search for GMCs in a typical Milky Way progenitor at z = 1.036. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we mapped the CO(4-3) emission of this gravitationally lensed galaxy at high resolution, reading down to 30 parsecs, which is comparable to the resolution of CO observations of nearby galaxies(5). We identify 17 molecular clouds, characterized by masses, surface densities and supersonic turbulence all of which are 10-100 times higher than present-day analogues. These properties question the universality of GMCs(6) and suggest that GMCs inherit their properties from ambient interstellar medium. The measured cloud gas masses are similar to the masses of stellar clumps seen in the galaxy in comparable numbers(7). This corroborates the formation of molecular clouds by fragmentation of distant turbulent galactic gas disks(8,9), which then turn into stellar clumps ubiquitously observed in galaxies at 'cosmic noon' (ref.(10).
Description: The ALMA raw data of the Cosmic Snake arc are available through the ALMA archive under the project identification 2013.1.01330.S. The HST images of MACS J1206.2–0847 are part of the CLASH, available at https://archive.stsci.edu/prepds/clash/. The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.The reduction of the ALMA data was performed with the CASA pipeline version 4.2.2, available at https://almascience.eso.org/processing/science-pipeline. The PdBI data were reduced using GILDAS software, available at http://www.iram.fr/IRAMFR/GILDAS. The lens model was obtained using Lenstool, publicly available at https://projets.lam.fr/projects/lenstool/wiki. The spectral energy distribution fitting was performed with a modified version of the Hyperz code, available in its original form at https://ascl.net/1108.010.
URI: http://hdl.handle.net/20.500.12666/324
E-ISSN: 2397-3366
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