Volume 625, May 2019
|Number of page(s)||20|
|Published online||21 May 2019|
MUSE unravels the ionisation and origin of metal-enriched absorbers in the gas halo of a z = 2.92 radio galaxy⋆
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
2 Centro de Astrobiologia (CSIC-INTA), Carretera de Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid, Spain
3 Astro-UAM, UAM, Unidad Asociada CSIC, Facultad de Ciencias, Campus de Cantoblanco, 28049 Madrid, Spain
4 Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, Porto 4150-762, Portugal
5 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany
6 Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
7 Institut d’Astrophysique de Paris, UMR 7095, CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
8 International Centre for Radio Astronomy Research, Curtin University, 1 Turner Avenue, Bentley, Western Australia 6102, Australia
9 Dunlap Institute for Astronomy & Astrophysics, 50 St. George Street, Toronto, ON M5S 3H4, Canada
Accepted: 9 April 2019
We have used the Multi-Unit Spectroscopic Explorer (MUSE) to study the circumgalactic medium (CGM) of a z = 2.92 radio galaxy, MRC 0943−242 by parametrising its emitting and absorbing gas. In both Lyα λ1216 and He II λ1640 lines, we observe emission with velocity shifts of Δv ≃ −1000 km s−1 from the systemic redshift of the galaxy. These blueshifted components represent kinematically perturbed gas that is aligned with the radio axis, and is therefore a signature of jet-driven outflows. Three of the four known Lyα absorbers in this source are detected at the same velocities as C IV λλ1548, 1551 and N V λλ1239, 1243 absorbers, proving that the gas is metal-enriched more so than previously thought. At the velocity of a strong Lyα absorber which has an H I column of NH I/cm−2 = 1019.2 and velocity shift of Δv ≃ −400 km s−1, we also detect Si II λ1260 and Si II λ1527 absorption, which suggests that the absorbing gas is ionisation bounded. With the added sensitivity of this MUSE observation, we are more capable of adding constraints to absorber column densities and consequently determining what powers their ionisation. To do this, we obtain photoionisation grid models in CLOUDY which show that AGN radiation is capable of ionising the gas and producing the observed column densities in a gas of metallicity of Z/Z⊙ ≃ 0.01 with a nitrogen abundance a factor of 10 greater than that of hydrogen. This metal-enriched absorbing gas, which is also spatially extended over a projected distance of r ≳ 60 kpc, is likely to have undergone chemical enrichment through stellar winds that have swept up metals from the interstellar-medium and deposited them in the outer regions of the galaxy’s halo.
Key words: galaxies: active / galaxies: individual: MRC 0943−242 / galaxies: halos / ISM: jets and outflows
The reduced datacube is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A102
© ESO 2019
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