Planck’s dusty GEMS

V. Molecular wind and clump stability in a strongly lensed star-forming galaxy at z = 2.2^⋆

¹ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
e-mail: canameras@dark-cosmology.dk
² Institut d’Astrophysique Spatiale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 121, 91405 Orsay, France
³ Aix Marseille Université, CNRS, CNES, LAM, Marseille, France
⁴ European Southern Observatory, ESO Vitacura, Alonso de Cordova 3107, Casilla 19001, Santiago, Vitacura, Chile
⁵ Atacama Large Millimeter/submillimeter Array, ALMA Santiago Central Offices, Alonso de Cordova 3107, Casilla 763-0355, Santiago, Vitacura, Chile
⁶ Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
⁷ Laboratoire AIM, CEA/DSM/IRFU, CNRS, Université Paris-Diderot, Bât. 709, 91191 Gif-sur-Yvette, France
⁸ Harvard-Smithsonian Center for Astrophysics, 02138 Cambridge, MA, USA
⁹ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, 6658 Vancouver, British Columbia, Canada

Received: 19 June 2018
Accepted: 20 September 2018

Abstract

We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 10⁹ M_⊙, in the strongly gravitationally lensed submillimeter galaxy “the Emerald” (PLCK_G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4–3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9 × 10¹⁰ M_⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4–3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of –200 km s⁻¹ is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.