Ultrafaint [C ii] Emission in a Redshift = 2 Gravitationally Lensed Metal-poor Dwarf Galaxy

Matus Rybak, E. Da Cunha, B. Groves, J. A. Hodge, M. Aravena, M. Maseda, L. Boogaard, D. Berg, S. Charlot, R. Decarli, D. K. Erb, E. Nelson, C. Pacifici, K. B. Schmidt, F. Walter, A. Van Der Wel

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4 Citations (Scopus)


Extreme emission-line galaxies (EELGs) at redshift z = 1-2 provide a unique view of metal-poor, starburst sources that are the likely drivers of the cosmic reionization at z ≥ 6. However, the molecular gas reservoirs of EELGs - the fuel for their intense star formation - remain beyond the reach of current facilities. We present ALMA [C ii] and PdBI CO(2-1) observations of the z = 1.8, strongly lensed EELG SL2S 0217, a bright Lyα emitter with a metallicity 0.05 Z o˙. We obtain a tentative (∼3σ-4σ) detection of the [C ii] line and set an upper limit on the [C ii]/SFR (star-forming rate) ratio of ≤1 106 L o˙/(M o˙ yr-1), based on the synthesized images and visibility-plane analysis. The CO(2-1) emission is not detected. Photoionization modeling indicates that up to 80% of the [C ii] emission originates from neutral or molecular gas, although we cannot rule out that the gas is fully ionized. The very faint [C ii] emission is in line with both nearby metal-poor dwarfs and high-redshift Lyα emitters, and predictions from hydrodynamical simulations. However, the [C ii] line is 30 fainter than predicted by the De Looze et al. [C ii]-SFR relation for local dwarfs, illustrating the danger of extrapolating locally calibrated relations to high-redshift, metal-poor galaxies.

Original languageEnglish
Article number130
Number of pages11
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 10 Mar 2021


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