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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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posted on 2023-06-08, 17:23 authored by Q Tan, E Daddi, Mark Sargent, G Magdis, J Hodge, M Béthermin, F Bournaud, C Carilli, H Dannerbauer, M Dickinson, D Elbaz, Y Gao, G Morrison, F Owen, M Pannella, D Riechers, F Walter
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.

History

Publication status

  • Published

File Version

  • Published version

Journal

Astrophysical Journal Letters

ISSN

2041-8205

Publisher

American Astronomical Society

Issue

2

Volume

776

Page range

L24

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2014-05-21

First Open Access (FOA) Date

2014-05-21

First Compliant Deposit (FCD) Date

2014-05-21

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