The complex multi-component outflow of the Seyfert galaxy NGC 7130

Comerón, S.; Knapen, J. H.; Ramos Almeida, C.; Watkins, A. E.
Referencia bibliográfica

Astronomy and Astrophysics

Fecha de publicación:
Active galactic nuclei (AGN) are a key ingredient for understanding galactic evolution, as their activity is coupled to the host galaxy properties through feedback processes. AGN-driven outflows are one of the manifestations of this feedback. The laser guide star adaptive optics mode for MUSE at the VLT now permits us to study the innermost tens of parsecs of nearby AGN in the optical. We present a detailed analysis of the ionised gas in the central regions of NGC 7130, which is an archetypical composite Seyfert and nuclear starburst galaxy at a distance of 64.8 Mpc. We achieve an angular resolution of 0.​​″17, corresponding to roughly 50 pc. We performed a multi-component analysis of the main interstellar medium emission lines in the wavelength range of MUSE and identified nine kinematic components, six of which correspond to the AGN outflow. The outflow is biconic, oriented in an almost north-south direction, and has velocities of a few 100 km s-1 with respect to the disc of NGC 7130. The lobe length is at least 3″(∼900 pc). We decomposed the approaching side of the outflow into a broad and a narrow component with typical velocity dispersions below and above ∼200 km s-1, respectively. The blueshifted narrow nomponent has a sub-structure, in particular a collimated plume traced especially well by [O III]. The plume is aligned with the radio jet, indicating that it may be jet powered. The redshifted lobe is composed of two narrow components and a broad component. An additional redshifted component is seen outside the main north-south axis, about an arcsecond east of the nucleus. Line ratio diagnostics indicate that the outflow gas in the north-south axis is AGN powered, whereas the off-axis component has LINER properties. We hypothesise that this is because the radiation field that reaches off-axis clouds has been filtered by clumpy ionised clouds found between the central engine and the low-ionisation emitting region. If we account for all the outflow components (the blueshifted components), the ionised gas mass outflow rate is Ṁ = 1.5 ± 0.9 M☉ yr-1 (Ṁ = 0.55 ± 0.55 M☉ yr-1), and the kinetic power of the AGN is Ėkin = (3.4 ± 2.5) × 1041 erg s-1 (Ėkin = (8.8 ± 5.9) × 1040 erg s-1), which corresponds to Fkin = 0.15 ± 0.11% (Fkin = 0.040 ± 0.027%) of the bolometric AGN power. The broad components, those with a velocity dispersion of σ > 200 km s-1, carry ∼2/3 (∼90%) of the mass outflow, and ∼90% (∼98%) of the kinetic power. The combination of high-angular-resolution integral field spectroscopy and a careful multi-component decomposition allows a uniquely detailed view of the outflow in NGC 7130, illustrating that AGN kinematics are more complex than those traditionally derived from less sophisticated data and analyses.

Based on observations made at the European Southern Observatory using the Very Large Telescope under programmes http://60.A-9100(K) and http://60.A-9493(A).

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