# Ultra-bright CO and [CI] emission in a lensed z=2.04 submillimeter galaxy with extreme molecular gas properties

## TL;DR

This study reports the detection of extremely bright molecular gas emission in a strongly lensed galaxy at z=2.04, revealing its starburst nature and extreme gas properties, and establishing it as a key reference for galaxy evolution studies.

## Contribution

First detection of the brightest CO(3-2) emission in a SMG, with detailed multi-transition analysis revealing extreme molecular gas properties and starburst activity at high redshift.

## Key findings

- Brightest CO(3-2) detection in a SMG to date
- Star formation efficiency around 100 L_sun (K km s^-1 pc^2)
- Gas depletion time approximately 60 Myr

## 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 submm/radio but significantly higher fluxes than the well-known lensed SMG SMMJ 2135, the Cosmic Eyelash at z=2.3. The interferometric observations identify unambiguously the location of the molecular line emission in two components, component CO32-A with I_CO(3-2)=52.2+-0.9 Jy km s^-1 and component CO32-B with I_CO(3-2)=15.7+-0.7 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 a SMG. In addition, we present follow-up observations of the brighter component with the Green Bank Telescope (CO(1-0) transition) and IRAM 30m telescope (CO(4-3) and [CI](1-0) transitions). The star-formation efficiency of ~100 L_sun (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 approx. 2000 M_sun yr^-1 and gas fraction M_mol/M_star=0.44 indicates a starburst/merger triggered star-formation. The obtained data of the cold ISM - from CO(1-0) and dust continuum - indicates a gas mass M_mol~15x10^11 M_sun for component CO32-A. Its unseen brightness offers the opportunity to establish the Cosmic Eyebrow as a new reference source at z=2 for galaxy evolution.