Volume 622, February 2019
|Number of page(s)||28|
|Published online||12 February 2019|
The MAGNUM survey: different gas properties in the outflowing and disc components in nearby active galaxies with MUSE⋆
Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy
2 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50157 Firenze, Italy
3 Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
4 University of California Observatories – Lick Observatory, University of California Santa Cruz, 1156 High St., Santa Cruz, CA 95064, USA
5 Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
6 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK
7 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
8 INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
9 INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
10 INAF – Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34143 Trieste, Italy
11 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
12 Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
13 European Southern Observatory, Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile
Accepted: 16 November 2018
We investigated the interstellar medium (ISM) properties of the disc and outflowing gas in the central regions of nine nearby Seyfert galaxies, all characterised by prominent conical or biconical outflows. These objects are part of the Measuring Active Galactic Nuclei Under MUSE Microscope (MAGNUM) survey, which aims to probe their physical conditions and ionisation mechanism by exploiting the unprecedented sensitivity of the Multi Unit Spectroscopic Explorer (MUSE), combined with its spatial and spectral coverage. Specifically, we studied the different properties of the gas in the disc and in the outflow with spatially and kinematically resolved maps by dividing the strongest emission lines in velocity bins. We associated the core of the lines with the disc, consistent with the stellar velocity, and the redshifted and the blueshifted wings with the outflow. We measured the reddening, density, ionisation parameter, and dominant ionisation source of the emitting gas for both components in each galaxy. We find that the outflowing gas is characterised by higher values of density and ionisation parameter than the disc, which presents a higher dust extinction. Moreover, we distinguish high- and low-ionisation regions across the portion of spatially resolved narrow-line region (NLR) traced by the outflowing gas. The high-ionisation regions characterised by the lowest [N II]/Hα and [S II]/Hα line ratios generally trace the innermost parts along the axis of the emitting cones where the [S III]/[S II] line ratio is enhanced, while the low-ionisation regions follow the cone edges and/or the regions perpendicular to the axis of the outflows, also characterised by a higher [O III] velocity dispersion. A possible scenario to explain these features relies on the presence of two distinct populations of line emitting clouds: one is optically thin to the radiation and is characterised by the highest excitation, while the other is optically thick and is impinged by a filtered, and thus harder, radiation field which generates strong low-excitation lines. The highest values of [N II]/Hα and [S II]/Hα line ratios may be due to shocks and/or a hard filtered radiation field from the active galactic nucleus.
Key words: galaxies: ISM / galaxies: Seyfert / galaxies: jets
The maps of the derived quantities shown in the Appendix (FITS files) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/A146
© ESO 2019
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