A deep search for molecular gas in two massive Lyman break galaxies at z=3 and 4: vanishing CO-emission due to low metallicity? - Archive ouverte HAL Access content directly
Journal Articles The Astrophysical journal letters Year : 2013

A deep search for molecular gas in two massive Lyman break galaxies at z=3 and 4: vanishing CO-emission due to low metallicity?

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Emanuele Daddi
  • Function : Author
  • PersonId : 837613
Helmut Dannerbauer
Mark Dickinson
Fabian Walter

Abstract

We present deep IRAM Plateau de Bure Interferometer (PdBI) observations, searching for CO-emission toward two massive, non-lensed Lyman break galaxies (LBGs) at z=3.216 and 4.058. With one low significance CO detection (3.5$\sigma$) and one sensitive upper limit, we find that the CO lines are >~ 3-4 times weaker than expected based on the relation between IR and CO luminosities followed by similarly, massive galaxies at z=0-2.5. This is consistent with a scenario in which these galaxies have low metallicity, causing an increased CO-to-H$_2$ conversion factor, i.e., weaker CO-emission for a given molecular (H$_2$) mass. The required metallicities at z>3 are lower than predicted by the fundamental metallicity relation (FMR) at these redshifts, consistent with independent evidence. Unless our galaxies are atypical in this respect, detecting molecular gas in normal galaxies at z>3 may thus remain challenging even with ALMA.
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Dates and versions

cea-00998688 , version 1 (06-01-2021)

Identifiers

Cite

Qinghua Tan, Emanuele Daddi, Mark T. Sargent, Georgios Magdis, Jacqueline A. Hodge, et al.. A deep search for molecular gas in two massive Lyman break galaxies at z=3 and 4: vanishing CO-emission due to low metallicity?. The Astrophysical journal letters, 2013, 776 (2), pp.L24. ⟨10.1088/2041-8205/776/2/L24⟩. ⟨cea-00998688⟩
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