Ultra-bright CO and [ ] Emission in a Lensed z = 2.04 Submillimeter Galaxy with Extreme Molecular Gas Properties

Abstract

We report the very bright detection of cold molecular gas with the IRAM NOEMA interferometer of the strongly lensed source WISE J132934.18+224327.3 at z  = 2.04, the so-called Cosmic Eyebrow. This source has a similar spectral energy distribution from optical-mid/IR to submillimeter/radio but significantly higher fluxes than the well-known lensed SMG SMMJ 2135, the Cosmic Eyelash at z  = 2.3. The interferometric observations unambiguously identify the location of the molecular line emission in two components, component CO32-A with Jy km s −1 and component CO32-B with Jy km s −1 . Thus, our NOEMA observations of the CO(3−2) transition confirm the SMG-nature of WISE J132934.18+224327.3, resulting in the brightest CO(3−2) detection ever of an SMG. In addition, we present follow-up observations of the brighter component with the Green Bank Telescope (CO(1−0) transition) and IRAM 30 m telescope (CO(4−3) and [C i ](1−0) transitions). The star formation efficiency of ∼100  L ☉ /(K km s −1 pc 2 ) is at the overlap region between merger-triggered and disk-like star formation activity and the lowest seen for lensed dusty star-forming galaxies. The determined gas depletion time ∼60 Myr, intrinsic infrared star formation SFR IR  ≈ 2000 M ⊙ yr −1 , and gas fraction M mol / M *  = 0.44 indicate a starburst/merger-triggered star formation. The obtained data of the cold ISM—from CO(1−0) and dust continuum—indicates a gas mass μM mol  ∼ 15 × 10 11 M ☉ for component CO32-A. Its unseen brightness offers us the opportunity to establish the Cosmic Eyebrow as a new reference source at z  = 2 for galaxy evolution.