Galactic winds with MUSE: A direct detection of Fe ii* emission from a z = 1.29 galaxy^⋆

¹ Université de Toulouse, UPS-OMP, 31400 Toulouse, France
e-mail: hayley.finley@irap.omp.eu
² IRAP, Institut de Recherche en Astrophysique et Planétologie, CNRS, 14 avenue Édouard Belin, 31400 Toulouse, France
³ IRAP, Institut de Recherche en Astrophysique et Planétologie, CNRS, 9 avenue Colonel Roche, 31400 Toulouse, France
⁴ Aix-Marseille Univ, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France
⁵ CRAL, Observatoire de Lyon, CNRS, Université Lyon 1, 9 avenue Ch. André, 69561 Saint-Genis Laval Cedex, France
⁶ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁷ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁸ ETH Zurich, Institute of Astronomy, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
⁹ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
¹⁰ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹¹ Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Golm, Germany

Received: 12 January 2017
Accepted: 31 May 2017

Abstract

Emission signatures from galactic winds provide an opportunity to directly map the outflowing gas, but this is traditionally challenging because of the low surface brightness. Using very deep observations (27 h) of the Hubble Deep Field South with the Multi Unit Spectroscopic Explorer (MUSE) instrument, we identify signatures of an outflow in both emission and absorption from a spatially resolved galaxy at z = 1.29 with a stellar mass M_⋆ = 8 × 10⁹M_⊙, star formation rate SFR = 77⁺⁴⁰_-25 M_⊙ yr^-1, and star formation rate surface brightness Σ_SFR = 1.6M_⊙ kpc^-2 within the [Oii] λλ3727,3729 half-light radius R_{1/2, [OII]} = 2.76 ± 0.17 kpc. From a component of the strong resonant Mg ii and Fe ii absorptions at −350 km s^-1, we infer a mass outflow rate that is comparable to the star formation rate. We detect non-resonant Fe ii* emission, at λ2365, λ2396, λ2612, and λ2626, at 1.2−2.4−1.5−2.7 × 10^-18 erg s^-1 cm^-2 respectively. The flux ratios are consistent with the expectations for optically thick gas. By combining the four non-resonant Fe ii* emission lines, we spatially map the Fe ii* emission from an individual galaxy for the first time. The Fe ii* emission has an elliptical morphology that is roughly aligned with the galaxy minor kinematic axis, and its integrated half-light radius, R_{1/2, Fe ii ∗} =4.1 ± 0.4 kpc, is 70% larger than the stellar continuum (R_1/2,⋆ ≃2.34 ± 0.17) or the [Oii] nebular line. Moreover, the Fe ii* emission shows a blue wing extending up to −400 km s^-1, which is more pronounced along the galaxy minor kinematic axis and reveals a C-shaped pattern in a p−v diagram along that axis. These features are consistent with a bi-conical outflow.