Planck’s Dusty GEMS

II. Extended [CII] emission and absorption in the Garnet at z = 3.4 seen with ALMA^⋆

¹ Institut d’Astrophysique Spatiale, Bât. 121, 91405 Orsay Cedex, France
e-mail: nicole.nesvadba@ias.u-psud.fr
² CNRS, France
³ Université Paris-Sud, France
⁴ Université Paris-Saclay, France
⁵ European Southern Observatory, ESO Vitacura, Alonso de Cordova 3107, Vitacura, Casilla 19001 Santiago, Chile
⁶ Atacama Large Millimeter/submillimeter Array, ALMA Santiago Central Offices, Alonso de Cordova 3107, Vitacura, Casilla 763-0355 , Santiago, Chile
⁷ Université de Toulouse, UMS-OMP, IRAP, 31028 Toulouse Cedex 4, France
⁸ LERMA, UMR 8112 CNRS, École Normale Supérieure and Observatoire de Paris, 75000 Paris, France
⁹ Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
¹⁰ Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
¹¹ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
¹² CEA-Saclay, 91191 Gif-sur-Yvette, France
¹³ School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
¹⁴ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, 6658 British Columbia, Canada

Received: 1 June 2016
Accepted: 20 July 2016

Abstract

We present spatially resolved ALMA [CII] observations of the bright (flux density S₃₅₀ = 400 mJy at 350 μm), gravitationally lensed, starburst galaxy PLCK G045.1+61.1 at z = 3.427, the “Garnet”. This source is part of our set of “Planck’s Dusty GEMS”, discovered with the Planck’s all-sky survey. Two emission-line clouds with a relative velocity offset of ~600 km s^-1 extend towards north-east and south-west, respectively, of a small, intensely star-forming clump with a star-formation intensity of 220 M_⊙ yr^-1 kpc^-2, akin to maximal starbursts. [CII] is also seen in absorption, with a redshift of +350 km s^-1 relative to the brightest CO component. [CII] absorption has previously only been found in the Milky Way along sightlines toward bright high-mass star-forming regions, and this is the first detection in another galaxy. Similar to Galactic environments, the [CII] absorption feature is associated with [CI] emission, implying that this is diffuse gas shielded from the UV radiation of the clump, and likely at large distances from the clump. Since absorption can only be seen in front of a continuum source, the gas in this structure can definitely be attributed to gas flowing towards the clump. The absorber could be part of a cosmic filament or merger debris being accreted onto the galaxy. We discuss our results also in light of the on-going debate of the origin of the [CII] deficit in dusty star-forming galaxies.