MAGNUM survey: compact jets causing large turmoil in galaxies -- Enhanced line widths perpendicular to radio jets as tracers of jet-ISM interaction

Outflows accelerated by the radiation pressure of AGN or by their kinetically powerful ($\gtrsim10^{44-45}$ erg/s) jets are commonly observed along AGN ionisation cones and jets. Recent works found that also low kinetic power jets ($\lesssim10^{44}$ erg/s) are able to accelerate such outflows. We study the relation between radio jets and ionised gas distribution and kinematics in IC 5063, NGC 5643, NGC 1068 and NGC 1386, as part of our MAGNUM survey of nearby Seyfert galaxies. These objects all host a small-scale ($\lesssim$1 kpc) low-power ($\lesssim10^{44}$ erg/s) radio jet, at small inclinations ($\lesssim$45{\deg}) on the galaxy disc. We employ optical/near-IR integral field spectroscopic observations from MUSE at VLT to obtain emission-line flux, kinematic and excitation maps of the ionised gas, that we compare with archival radio images and Chandra X-ray data. We detect a strong (up to $\gtrsim800-1000$ km/s), extended ($\gtrsim$1 kpc) and shock-excited emission-line velocity width enhancement perpendicularly to the AGN ionisation cones and jets in all the four targets. Such broad, symmetric line profiles are not associated with a single coherent net velocity of the gas, differently from the"classical"asymmetric-line, high-velocity outflow observed along the ionisation cones and jets. Recent works found similar line velocity width enhancements perpendicularly to the ionisation cones in other AGN, all hosting a low-power jet aligned with the cones and showing evidence of interaction with the galaxy disc material. We interpret the observed phenomenon as due to the action of the jets perturbing the gas in the galaxy disc. In fact, such extended line width enhancement perpendicular to AGN cones and jet is observed only in galaxies hosting a low-power jet whose inclination is low enough on the galaxy disc to strongly impact on its material, as also recent simulations predict.


Introduction
Outflows and jets accelerated by active galactic nuclei (AGN) are considered to have an important role in galaxy evolution ("feed- back" effect; e.g. Fabian 2012 for a review). In the standard picture of AGN-driven winds the AGN radiation pressure and/or magnetic fields can accelerate outflows which are able to expel large quantities of gas out of galaxies and consequently deplete the gas reservoir needed to form stars ("radiative" mode feedback), leaving a red and dead galaxy, while jets in a following and longer phase keep the gas in the galaxy halo hot preventing Article number, page 1 of 19 arXiv:2011.04677v1 [astro-ph.GA] 9 Nov 2020 A&A proofs: manuscript no. linewidth_perpend_jets Notes. (a) Total exposure time on object T exp , given by the combination of the single n exp -times repeated exposures having duration of t exp each. (b) Exposure time of each dedicated sky exposure times the number of exposures. (c) After comparing the two datasets from program 60.A-9339 and 095.B-0532 for NGC 5643, we employed for this work the observations from program 095.B-0532 due to their superior seeing compared to those from program 60. A-9339. (d) The first OB suffered, in the central spaxels, from emission lines being saturated or in the non-linear response regime of the instrument. The second Observing Block (OB) was then acquired with shorter exposure times (100s instead of 500s) and only this second OB has been adopted in the central spaxels. Notes. (a) Distance of the galaxy from Earth, obtained from http://leda.univ-lyon1.fr/ best distance modulus, i.e. the weighted average between the redshift distance modulus corrected for infall of the Local Group towards Virgo and the weighted average of the published redshift-independent distance measurements. (b) Central portion of the galaxy covered by MUSE ∼1 ×1 FOV. (c) Spatial scale at the distance of the galaxy.
re-accretion and re-ignition of star formation ("kinetic" mode feedback). However, strong jets can also be responsible for the acceleration of powerful outflows by pushing the gas in their direction of propagation (e.g. Nesvadba et al. 2008, Vayner et al. 2017. Some studies (e.g. Combes et al. 2013, García-Burillo et al. 2014, Cresci et al. 2015b, Harrison et al. 2015, Morganti et al. 2015, Molyneux et al. 2019 revealed that this phenomenon can occur not only in the traditional "radio loud" objects 1 , having powerful jets, but also in galaxies hosting low-power 2 , compact radio jets, typically classified as "radio quiet". Some of these works showed an interaction between the low-power jet and the gas in the galaxy disc (e.g. García-Burillo et al. 2014, Morganti et al. 2015, Cresci et al. 2015b. In this paper we present data of four nearby ( 50 Mpc) Seyfert galaxies hosting low-luminosity radio jets, obtained with the optical and near-IR spectrograph Multi Unit Spectroscopic Explorer (MUSE; Bacon et al. 2010) at the Very Large Telescope (VLT), part of European Southern Observatory's (ESO) Paranal Observatory. In these four objects we find that the low-power jets appear to strongly interact with the gas in the disc, driving a peculiar turbulent phenomenon perpendicularly to their direction of propagation.
The four sources presented in this work belong to the MAG-NUM survey (Measuring Active Galactic Nuclei Under MUSE 1 The radio loudness is commonly defined based on R = L ν 5 GHz /L ν 4400 Å , ratio between the monochromatic radio luminosity at 5 GHz and the optical one at 4400 Å. An object is defined as "radio loud" if R > 10, "radio quiet" otherwise (e.g. Kellermann et al. 1989). Alternatively, objects are classified as radio quiet when their radio luminosity (either at 5 GHz, e.g. Kellermann et al. 1994, Xu et al. 1999, or at 1.4 GHz, e.g. Padovani 2017, Wylezalek & Morganti 2018) is 10 24 W/Hz. 2 Through the paper, with jet power we mean the kinetic power of the jet, not the power (luminosity) of its radio emission, if not stated otherwise.
Microscope), which targets nearby Seyfert galaxies with MUSE at VLT. An overview of the survey, which already produced a number of publications (Cresci et al. 2015b, Venturi et al. 2018, Mingozzi et al. 2019, can be found in Venturi et al. (2017). A detailed presentation will be the subject of a forthcoming paper (Venturi et al., in prep.).

MUSE data description and analysis
The MUSE data of the four galaxies belong to different programmes, as detailed in Table 1. Each exposure was dithered by 1 and/or rotated by 90 • relative to one another. All the observations were acquired in seeing-limited wide field mode (WFM), covering 1 × 1 with a sampling of 0.2 /spaxel, and nominal mode, spanning the spectral range 4750−9350 Å. The side of MUSE field of view (FOV hereafter) spans a range of ∼3.3 to 14 kpc in these four galaxies.
The data reduction and exposure combination were carried out by using the ESO MUSE pipeline (Weilbacher et al. 2020) version v1.6. Depending on the galaxy, this was done either making use of self-made scripts executing the Common Pipeline Library (CPL; Banse et al. 2004, ESO CPL Development Team 2014 reduction recipes with EsoRex (ESO Recipe Execution Tool; ESO CPL Development Team 2015) or employing ESO Reflex (Recipe flexible execution workbench, Freudling et al. 2013), which gives a graphical and automated way to perform the reduction (still operated by EsoRex using the CPL recipes), within the Kepler workflow engine (Altintas et al. 2004). For NGC 5643 we adopted the reduced cube provided by ESO Quality Control Group. The different reduction softwares used do not give any measurable difference on the final reduced cubes since, given the default reduction strategy (i.e. correction for instrumental and atmospheric effects and sky subtraction), they all rely on the same recipes run with EsoRex. Due to the extension of the source emission, filling the entire MUSE FOV, dedicated offset sky observations pointed towards regions free of galaxy emission were employed (see Table 1).
The data analysis was executed by using custom Python scripts, following an approach similar to that described in Venturi et al. (2018), Mingozzi et al. (2019) and Marasco et al. (2020). We briefly summarise it in the following. A more detailed explanation of the analysis procedure employed for all the sources in the MAGNUM survey will be given in a forthcoming paper (Venturi et al., in prep.).
We first fitted and subtracted the stellar continuum from each spaxel. To do so, we initially performed a Voronoi adaptive binning (Cappellari & Copin 2003) on the cube, to achieve a minimum signal-to-noise ratio (S/N) per bin on the continuum. We set the minimum S/N per bin to an average value of 50 per wavelength channel, considering the signal and associated noise below 5530 Å, where stellar absorption features are more prominent, and excluded gas emission lines. We then fitted the stellar continuum in each bin through the ppxf code (Penalized PiXel-Fitting; Cappellari & Emsellem 2004) in the range 4770−6800 Å using a linear combination of Vazdekis et al. (2010)  , with the only goal of better constraining the underlying stellar continuum. We then subtracted spaxel-by-spaxel the fitted stellar continuum after having rescaled the modelled continuum to the median of the observed continuum in each spaxel.
At this point we fitted the above mentioned gas emission lines from the continuum-subtracted cube, by using the mpfit routine (Markwardt 2009). We adopted one, two or three Gaussians to reproduce the emission line profiles, as determined by a reduced-χ 2 criterion, so as to use multiple components only in case of complex profile shapes (a more detailed description will be given in Venturi et al., in prep.). For each separate Gaussian component, we required all the emission lines to have the same velocity and velocity dispersion, and fixed to the theoretical value of 3 the flux ratios between the strongest and the fainest lines of the We finally produced emission line maps for the emission lines from the total modelled profile made up of the sum of the fitted Gaussians. The maps are presented in Sect. 3.

MUSE maps
In this section we show the maps obtained from the analysis of the MUSE data of IC 5063, NGC 5643, NGC 1068 and NGC 1386, which, as introduced before, reveal a peculiar phenomenon that we present and discuss in the following. A S/N cut of 3 per spaxel on the emission lines involved in the maps was applied 4 . We also excluded deviant spaxels in which a wrong fit resulted in extremely broad wings fitting the noise, by setting a maximum value on the fitted velocity dispersion (varying from 350−450 km/s depending on the galaxy) in spaxels with low S/N in the wings. This was done so as to carefully exclude only spurious high velocity dispersions and not real ones.

IC 5063
IC 5063 is an S0 early-type galaxy residing at a distance of ∼46 Mpc from Earth (1 ∼ 220 pc). With a radio power of P 1.4 GHz = 3 × 10 23 W Hz −1 (Tadhunter et al. 2014), it is one of the brightest Seyfert galaxies in the radio, though still being radio quiet. IC 5063 hosts a radio jet limited to the inner ∼1 kpc of the galaxy along its major axis (∼0.5 kpc per side), which drives an outflow of neutral atomic (Morganti et al. 1998, Oosterloo et al. 2000, molecular (Morganti et al. 2013, Tadhunter et al. 2014, Morganti et al. 2015, Dasyra et al. 2016, Oosterloo et al. 2017) and ionised gas (Morganti et al. 2007, Dasyra et al. 2015, Congiu et al. 2017 on the same scales along the jet direction by creating a cocoon of swept off gas. The jet is known to lie in the plane of the disc, as clear signs of jet-ISM interaction are observed in HI (Oosterloo et al. 2000), CO (Morganti et al. 2015) and H 2 (Tadhunter et al. 2014).
In Figs. 1 and 2 we report our MUSE flux and kinematic maps for IC 5063, respectively. The FOV of the MUSE observations (red box in Fig. 1a) covers a significant fraction of the galaxy, ∼14×14 kpc 2 . In the three colour image in Fig. 1b we report the [O iii] (green), Hα (red) and stellar continuum emission (blue). The [O iii] (also Fig. 1c) traces the large-scale 'X'-shaped AGN ionisation cone extending up to ∼10 kpc per side along the galaxy major axis (see also Colina et al. 1991, Morganti et al. 1998, Sharp & Bland-Hawthorn 2010. The brightest line emission stems from the active nucleus and from two lobes a few arcsec to the E and W of the nucleus (∼500 pc away per side), spatially consistent with the radio (e.g. Morganti et al. 1998 and Australia Telescope Compact Array (ATCA) 17.8 GHz contours in Fig. 1c, from Morganti et al. 2007) and X-ray lobes (Gómez-Guijarro et al. 2017).
To isolate the high-velocity outflowing gas, we report in Fig.  2a the [O iii] flux integrated in the velocity ranges [200,1000] km/s (receding) and [−1000,−200] km/s (approaching) of the fitted profile. We adopted the fitted stellar velocity in each pixel as zero velocity, so as to minimise the contribution to the flux from gas regularly rotating in the disc and maximise that of the highvelocity outflowing gas (following the same approach of Mingozzi et al. 2019). We point out that the stellar velocity dispersion varies from ∼100 km/s to a maximum of ∼170 km/s across the field of view, so ∼200 km/s represents a fairly appropriate threshold to separate rotating from outflowing material. The map shows that the ionised outflowing material, having high bulk velocity, is directed as the AGN ionisation cones and the radio jet.
However, by inspecting the map of the [O iii] line velocity width (measured through W70 5 ) in Fig. 2b, we notice an intriguing feature. The map shows in fact an elongated region of enhanced line width (up to ∼800 km/s at its centre; see also López-Cobá et al. 2020) perpendicular to the radio jet, AGN ionisation cones, X-ray emission and ionised and molecular outflow. This perpendicular enhanced line width is also very extended, spanning about 7 kpc (∼3.5 kpc per side), while the radio jet extends only over the central ∼1 kpc. On very small scales (∼ 1-2 ) Dasyra et al. (2015) also reported, in a few near-IR emission lines, a hint of velocity dispersion enhancement perpendicular to the radio jet and to the line-emission major axis. Our maps reveal that such small-scale enhancement, limited by signal-tonoise to the inner ∼ 1-2 in Dasyra et al. (2015), trace the base of a much larger (up to ∼ 35 ) and unambiguous velocity dispersion enhancement. In Fig. 3 we report two representative spectra extracted from the region of line width enhancement and from the direction of radio jet and ionisation cones, respectively. The former shows a broad, symmetric emission line profile, with W70 of ∼500 km/s ([O iii]) to ∼600 km/s (Hβ), close to the galaxy systemic velocity. The latter presents instead a narrower (∼200 km/s) profile with higher net velocity shift and asymmetric wings. We note in fact that the observed W70 enhancement is generally not associated to a coherent differential gas motion in the receding or approaching direction (suggestive of turbulent gas), the bulk of ionised gas with significant net velocity being instead in the jet and cones direction, as can be seen from Fig. 2a. This does not mean that the line profiles in the W70-enhanced region always have a centroid velocity comparable with the galaxy systemic velocity. However, they do not show a coherent velocity pattern with a definite net velocity on each side (either redshifted or blueshifted), as it is observed instead in the direction of jet and ionisation cones.
Moreover, in Figs. 2c and 2d we show the [O iii]/Hβ vs [S ii]/Hα spatially-resolved BPT diagnostic diagram (Veilleux & Osterbrock 1987; hereafter [S ii]-BPT), commonly employed to identify the dominant gas ionisation mechanism between AGN, star formation processes or shocks/LI(N)ER. Each point in the diagram (panel c) corresponds to a pixel in the associated map (panel d). Besides colour coding the BPT diagram and the map according to the dominant ionisation mechanism, we also set the intensity of the colour proportional to the [O iii] W70 (i.e. the line velocity width). The BPT map reveals that, while the AGN ionisation dominates in the bi-cones along the galaxy major axis, shock/LI(N)ER ionisation is present in the direction perpendicular to the jet and ionisation cones, where we observe the line width enhancement. This is consistent with Mingozzi et al. From the spatially-resolved BPT diagram in Fig. 2d, we also note the presence of an extended (by ∼ 15-20 ) star-forming stripe to the South-West of the nucleus, oriented perpendicularly to the direction of the galaxy minor axis. This can be seen in Hα also in Fig. 1b, showing a clumpy morphology (see also López-Cobá et al. 2020). Its velocities are consistent with those of the rotating disc (see the disc-outflow separation in Mingozzi et al. 2019). Interestingly, this star-forming stripe lies at the southwestern edge of the line width enhancement (Fig. 2b), perpendicularly to its direction and broadly centred on its axis. Their relative spatial location can be better seen in Fig. A.2 in Appendix where, for improved visual clarity, we report the map of Hα emission with the contours of [O iii] W70 superimposed. In principle, it cannot be excluded that the turbulent gas exhibiting the large emission line widths could be responsible for favouring the observed star formation, through compression and fragmentation of the impacted gas clouds, as in the "positive feedback" mechanism from outflows and jets (e.g. Silk 2013, Zubovas et al. 2013, Cresci et al. 2015b, Cresci et al. 2015a, Santoro et al. 2016). However, the study of this possible case of positive feedback goes beyond the scope of this paper and would require a focused deeper investigation.
Interestingly, we note that low spatial resolution 1.4 GHz radio data from Morganti et al. (1998) show extended emission on scales of ∼ 40 whose major axis is in the same direction of the W70 enhancement that we observe, perpendicularly to the small-scale high-resolution radio jet. The nature of this extended perpendicular radio emission is unclear. Given its direction and scale, it might be related to the line width enhancement that we observe.
A recent work by Maksym et al. (2020b) also discovered fanshaped dark radial rays (similar to the crepuscular rays observed at sunset on Earth) in the direction perpendicular to the galaxy major axis and AGN ionisation cones. These extend on scales of ∼ 1 arcmin, comparable with those of the MUSE observations presented in our work. Among the different possible interpretations they provide for the dark rays, they propose dusty reflection of AGN emission escaping in the direction perpendicular to the ionisation cones, with the dark rays either given by the lack of reflecting dust or by the excess of absorbing dust. In this case, the phenomenon observed in Maksym et al. (2020b) and the enhanced emission line widths that we observe in the same direction and scales might be part of the same phenomenon (possibly also together with the large-scale radio emission from Morganti et al. 1998 mentioned above), with the dust entrained in the turbulent material -traced by the enhanced line widths -giving rise to the dark rays.

NGC 5643
NGC 5643 (D ∼ 16 Mpc; 1 ∼ 78 pc) is a barred radio-quiet (Leipski et al. 2006) Seyfert 2 galaxy, almost face-on. It hosts an ionisation cone extending over a few kpc eastward of the nucleus (e.g. Schmitt et al. 1994, Simpson et al. 1997) and inclined by ∼40 • to the galaxy disc, according to the model by Fischer et al. (2013). An outflow along the cone was found in [O iii] with MUSE by Cresci et al. (2015b) (as part of MAGNUM survey), who also detected the western side of the ionisation bi-cone. The galaxy also hosts a low-luminosity bipolar radio jet aligned with the ionisation cones and on similar scales, spanning ∼25-30 (∼2 kpc; Morris et al. 1985, Leipski et al. 2006, which is interacting with the galaxy disc (Cresci et al. 2015b, Alonso-Herrero et al. 2018, García-Bernete et al. 2020. Figs. 4 and 5 display our MUSE flux and kinematic maps for NGC 5643, respectively. Fig. 4a contains an image of the entire galaxy where the FOV of our MUSE maps, covering the central ∼5×5 kpc 2 , is reported in red. In the three-colour MUSE image in Fig. 4b we show the bright [O iii] ionisation bi-cone (green), stronger to the E of the nucleus than to the W, and Hα emission (red), tracing star formation. In Fig. 4c we report the [O iii] emission together with the 8.4 GHz radio contours from the Karl G. Jansky Very Large Array (VLA) presented in Leipski et al. (2006). The [O iii] cones and the radio jet are co-spatial and aligned in the E-W direction. Fig. 5a reports the ±|200-1000| km/s high-velocity ionised gas, showing that the bulk of the fast outflowing material is aligned co-spatially with the AGN bi-cone and the radio jet as discussed in Cresci et al. (2015b). The stellar velocity dispersion ranges from ∼60 km/s to ∼100 km/s across the FOV, making 200 km/s a safe threshold to exclude the contribution from rotating material.
On the contrary, large values of the [O iii] line width (Fig.  5b), up to W70 ∼ 700 km/s, are observed in the N-S direction, perpendicularly to the ionisation cones and radio jet, over a distance of ∼1.5 kpc per side (∼3 kpc in total).
In Fig. 5c, d we also display the spatially-resolved [S ii]-BPT diagram, which shows that shock/LI(N)ER ionisation dominates in the direction of enhanced line velocity width perpendicular to radio jet and AGN ionisation cones (as found by Mingozzi et al. 2019), as in IC 5063.

NGC 1068
NGC 1068 is a nearby prototypical Seyfert 2 galaxy located at a distance of ∼ 10.5 Mpc from Earth (1 ∼ 51 pc). The galaxy also undergoes powerful starburst activity, mainly concentrated in a prominent starburst ring of ∼1-1.5 kpc radius (e.g. Schinnerer et al. 2000, García-Burillo et al. 2014) elongated in the NE-SW direction. Like IC 5063 it is one of the brightest Seyferts at radio wavelengths (P 1.4 GHz = 2×10 23 W Hz −1 , Ulvestad & Wilson 1984), though still being radio quiet (e.g. Prieto et al. 2010, Teng et al. 2011. NGC 1068 hosts a radio jet spanning up to ∼ 800 pc in the NE-SW direction (e.g. Gallimore et al. 1996, Krips et al. 2006. The jet and the AGN ionisation cones, oriented in the same direction, are inclined at ∼45 • with respect to the plane of the disc, such that also in this case the gas in the disc is illuminated by the AGN radiation and interacts with the jet (e.g. Cecil et al. 1990, Bland-Hawthorn et al. 1997, García-Burillo et al. 2014). An outflow indeed propagates in the same direction, detected in both the ionised (e.g. Axon et al. 1997, Crenshaw & Kraemer 2000, Cecil et al. 2002, Barbosa et al. 2014 and molecular gas (García-Burillo et al. 2014, Gallimore et al. 2016, driven by the AGN (García-Burillo et al. 2014). Extended X-ray emission is observed in the same direction on both sides of the nucleus, following the shape of the AGN cones (Bauer et al. 2015).
In Figs. 6 and 7 we show our MUSE flux and kinematic maps for NGC 1068, respectively. Fig. 6a shows on a large-scale image of the galaxy the FOV of our MUSE maps (red box), covering the central ∼3.3×3.3 kpc 2 . The MUSE three-colour image in Fig. 6b displays the Hα emission (red) which follows the spiral arms and the large circumnuclear star-forming ring. [O iii] emission (green) is instead prominent in the known bright inner ionisation cone (e.g. Macchetto et al. 1994) and in fainter outer lobes extending spirally from the inner one up to scales of ∼4.5 kpc both to the NE (brighter) and to the SW (fainter; see also Bland-Hawthorn et al. 1997, López-Cobá et al. 2020. This is consistent with the ionisation cones illuminating the spiralling gas in the disc, above it in case of the NE brighter cone, below it in case of the SW fainter cone. The spiral-like [O iii] emission roughly traces the extended X-ray emission (Bauer et al. 2015). Moreover, the [O iii] emission extends in the same direction as the radio jet (spanning about 5 arcsec per side), whose VLA 5 GHz (C band) A-array contours (from Gallimore et al. 1996) are reported in Fig. 6c.
Similarly to IC 5063 and NGC 5643, Fig. 7a shows that the bulk of the high-velocity gas is elongated in the same NE-SW direction as the [O iii] inner cone and the radio jet, tracing an outflow spatially consistent with the jet. The stellar velocity dispersion ranges from ∼60 km/s to ∼170 km/s across the FOV, thus 200 km/s is an appropriate demarcation between rotating and outflowing material. kpc. Same as in Fig. 1 for (b) and (c). The contours in (c) are the VLA 5 GHz (C band) A-array radio data from Gallimore et al. (1996). nucleus populate the area of the BPT diagram at high [S ii]/Hα ratios, which is indicative of shock/LI(N)ER ionisation.

Extended X-ray emission along the line width enhancement
To further investigate the presence of shocks perpendicularly to the AGN ionisation cones and jets, as inferred from spatially resolved BPT diagrams, we investigated the extended X-ray emission in this galaxy through Chandra ACIS-S data. NGC 1068 is the only target out of the four we analysed in this work whose archival Chandra observations have significant statistics along the minor axis of the AGN cones, in the region of line velocity width enhancement.
We have retrieved from the archive the highest quality Chandra observation of NGC 1068 (ObsID: 344), performed in February 2000. The data were reprocessed following the standard procedure with ciao v4.12 (Fruscione et al. 2006). We have extracted the spectrum from an annular sector lying to the NW of the nucleus (see Fig. 8), centred on the hard X-ray nuclear source and defined from 5 to 18 and position angles (from W to N) from 5 • to 60 • . This is spatially coincident with a portion of the W70 enhancement region (magenta contours). The circumnuclear X-ray emission of NGC 1068 is rather complex, and it was analysed in detail by Young et al. (2001). Similarly to the wider 'West' region considered by those authors (their Fig. 1), the spectrum from our annular sector shows a hard (2-8 keV) continuum component, and tentative evidence of an iron emission line. We modelled the spectrum within xspec v12.11 (Arnaud 1996) with two thermal components from collisionally ionised gas (apec; Smith et al. 2001), obtaining a barely acceptable fit with a C-statistics (Cash 1979) of 251/181. The soft, colder component has kT = 0.72 ± 0.02 keV and prefers a low metallicity (0.12 ± 0.02 solar); the hard, hotter one (kT > 5 keV, poorly constrained), instead, requires solar abundances in order to account for the iron line. Clear residuals are seen, especially, in the O vii and Si xiii Heα bands. We then replaced the hot thermal component with a shock one (pshock; Borkowski et al. 2001). The physical parameters of both components remain the same, but the fit significantly improves down to C-stat = 218/181. While this is not a conclusive proof of the presence of shocks in the W70 enhancement region, we note that the iron emission line falls in the Fe xxv-xxvi Kα band, which is not compatible with fluorescence from cold gas.
In conclusion, both MUSE BPT diagnostic diagrams and Chandra X-ray data suggest the presence of shocks in the region of enhanced W70 perpendicular to the AGN ionisation cones and the jet.

NGC 1386
NGC 1386 (D ∼ 16.4 Mpc; 1 ∼ 80 pc) is a radio-quiet (P 1.4 GHz 4.6 × 10 20 W Hz −1 , Ulvestad & Wilson 1984) Seyfert 2 spiral galaxy, inclined by ∼65 • with respect to the line of sight (Lena et al. 2015; see also Fig. 9a). Ferruit et al. (2000) reported two elongated emission-line structures over ∼2 to the N and S of the nucleus from [O iii] and Hα+[N ii] images, likely due to the AGN ionising radiation field illuminating the gas in the disc (Lena et al. 2015). Elongated radio emission, suggestive of a radio jet, is observed to the S of the nucleus across ∼1 (∼ 80 pc) and it is also marginally resolved to the N (Nagar et al. 1999, Mundell et al. 2009). Lena et al. (2015) found broad optical emissionline profiles in the perpendicular (E-W) direction across ∼2-3 , suggesting the presence of rotation and/or of an outflow in this direction.
In Figs. 9 and 10 we report our MUSE flux and kinematic maps for NGC 1386, respectively. The red box in Fig. 9a shows the ∼ 5.1 × 5.1 kpc 2 FOV of our MUSE maps superimposed on a large scale image of the entire galaxy. Fig. 9b displays our MUSE three-colour image.
Hα (red) dominates in a prominent circumnuclear starforming ring. Inside it, the [O iii] emission traces the entire N-S ionisation lobes spanning ∼200-300 pc per side, firstly reported by Ferruit et al. (2000), which further extend to fainter and clumpy emission-line structures towards the SE and NW in an 'S'-shaped pattern.
The bulk of high-velocity [O iii] emission, tracing an outflow of ionised gas, is mostly elongated in the N-S direction (Fig.  10a), following the [O iii] ionisation lobes and the radio jet. Being the stellar velocity dispersion across the galaxy in the range 60−130 km/s, the threshold of 200 km/s is appropriate to isolate the contribution of the outflow from that of the rotating disc.
The [O iii] line velocity width map (Fig. 10b) shows instead a strong and extended (over ∼1.5 kpc) enhancement, up to W70 > 600 km/s, almost perpendicularly to the ionisation lobes, the ionised outflow and the putative small-scale radio jet, indicating the presence of fast/turbulent motions away from the nucleus in this direction.
The [S ii]-BPT diagram and associated map for NGC 1386 (Fig. 10c, d) show that also in this case the gas in the direction of line velocity width enhancement (darker colours in the BPT map), perpendicularly to the narrow AGN ionisation lobes (which can be clearly seen in the N-S direction in panel d) and radio jet, is dominated by shock/LI(N)ER ionisation. Unfortunately, the BPT map for NGC 1386 is not visually straightforward and the shock/LI(N)ER-like ionisation does not stand out clearly in this perpendicular direction as it does instead in IC 5063 and NGC 5643. The circumnuclear star-forming ring dominates in fact the gas ionisation at about 5 to the East and West of the nucleus, masking the shock/LI(N)ER one, which on the other hand almost totally fills (aside from the AGN lobes) the area encompassed within the ring and outside it.

Discussion: Enhanced line velocity widths perpendicular to radio jets
We detect strongly enhanced line widths of [O iii] emission line profiles perpendicularly to radio jets and to the [O iii] ionisation cones in four galaxies of our sample, IC 5063, NGC 1386, NGC 5643 and NGC 1068. We note that these objects are the only ones out of the nine analysed so far from our MAGNUM survey which show evidence of a low-power ( 10 44 erg s −1 ) radio jet, interacting with the ISM of the host galaxy given its low inclination with respect to the disc. All the other objects in our sample do not show any evidence for such enhanced line velocity widths perpendicularly to their ionisation cones and to their high-velocity component tracing the outflowing gas (see e.g. Venturi et al. 2018for NGC 1365and Venturi et al. 2017. Interestingly, we do not detect this enhanced W70 feature from MUSE data either in Centaurus A, where a radio jet is present, or in Circinus, showing radio lobes possibly indicative of the presence of an (undetected) radio jet. Nevertheless, the nature and structure of the radio emission in these two objects are much different than in those presented in this work. Indeed, the radio lobes of Circinus are roughly perpendicular to the galaxy disc (Elmouttie et al. 1998, Mingo et al. 2012. Also in the radio loud Centaurus A the jet is directed perpendicularly to the galaxy disc and, additionally, it is in a much more evolved state, having outer lobes extending to ∼250 kpc (e.g. Israel 1998). However, given the high extinction in the central region of these two galaxies (see e.g. Mingozzi et al. 2019) we cannot completely exclude the presence of perturbed, high-W70 gas in their cores. Indeed, near-IR emission lines actually show in Centaurus A a velocity dispersion enhancement perpendicularly to the jet direction and aligned with the galaxy optical major axis (Neumayer et al. 2007), but on very small scales (∼1−2 , i.e. 20−40 pc), far different from the kpc-scale extension observed for the galaxies presented in this work. The authors interpret such small-scale velocity dispersion enhancement as due to an inclined nuclear hot gas disc, and successfully include it in a rotating disc model. However, in principle it cannot be excluded that also the base of the jet might be responsible for it. Circinus does not show instead any sign of a central enhanced line velocity width perpendicularly to the direction of the ionisation cone and radio lobes even from near-IR data (Müller-Sánchez et al. 2011).
A special consideration should be done for NGC 2992, also part of our survey. This object shows a mild enhancement of the gas velocity dispersion ( 150 km/s) in the near-IR in a slightly elliptical region along the galaxy major axis, limited to the central 1-2 (Müller- Sánchez et al. 2011, Friedrich et al. 2010 and a more extended enhancement in the same direction, along the dust lane, also in optical from MUSE data, still with low values ( 150 km/s, i.e. W70 300 km/s). Given that the elongation of the near-IR central enhanced velocity dispersion is along the disc major axis, it could simply be a projection of a circularly symmetric, slightly higher velocity dispersion around the galaxy centre. The same considerations just done for Centaurus A may apply also to NGC 2992, that is, a radio jet escaping perpendicularly from the disc may weakly perturb the gas in the disc around the jet base and give a modest increase in velocity dispersion in the very centre. NGC 2992 exhibits extra-planar radio emission, but no evidence for a jet in radio or X-rays (Irwin et al. 2017). The radio emission stems from two lobes on scales of ∼5 each (Ulvestad & Wilson 1984, Sebastian et al. 2020, which are, in projection, neither along the galaxy minor axis (i.e. perpendicular to the disc, given its high inclination in our line of sight) nor in the direction of its major axis. Polarised radio emission instead shows up in the minor axis direction (Irwin et al. 2017). Given the complexity of the source in terms of its radio emission and environment (it is also in interaction with a companion, NGC 2993) and the paucity of the velocity dispersion enhancement (both spatially and in velocity), its nature appears to be different from that of the galaxies presented in this work and found in literature (see Sect. 4.1), where we observe a strong and extended velocity dispersion enhancement perpendicularly to jets roughly co-planar with the galaxy disc. We thus have not included NGC 2992 in the objects presented in this work.
In the other galaxies belonging to our MAGNUM survey, which do not host a radio jet, we do not observe the strongly enhanced line velocity widths (see e.g. the W70 maps of NGC 4945 in Venturi et al. 2017and of NGC 1365in Venturi et al. 2018 that we find in the four jetted objects presented in this work. We stress that the W70 enhancement feature does not seem to be associated to the presence of ionisation-cone outflows, which are observed in all MAGNUM galaxies, or to a higher AGN power. For instance, the AGN luminosities (as traced by the Swift BAT 14-195 keV hard X-ray luminosity; Baumgartner et al. 2013) of NGC 4945 and NGC 1365, which do not host a jet nor exhibit the perpendicular line width enhancement phenomenon, are higher than those of NGC 1068 and NGC 5643. The presence of a jet at low inclinations with respect to the galaxy disc seems to be the only feature that the four galaxies studied in this work have in common.
The results we presented and all the considerations above suggest a correlation between the presence of a jet in its early phases, inclined low enough on the disc to significantly interact with the galaxy ISM, and the strongly enhanced line widths observed perpendicular to it, possibly indicating turbulent gas motions. In fact, the inclination angle of all these jets compared to the galaxy disc plane is small, thus the jets are expected to strongly interact with the galaxy disc during their propagation inside it, as opposed to the radio structures in Centaurus A and Circinus which are perpendicular to the galaxy disc.

Observation of the phenomenon in previous works
Enhanced line velocity widths perpendicular to radio jets (and to the AGN ionisation cones) are observed in a few other local Seyfert galaxies, which we recap in the following. We stress that this list is based on our search in literature and might thus be incomplete.
First, Couto et al. (2013) find in Arp 102B enhanced velocity dispersion of optical emission lines in a thick band perpendicularly to the radio jet and to the [O iii] emission axis, but opposite bulk gas velocities are also detected in the dispersion enhancement direction, which they alternatively interpret as either due to a small-scale bipolar outflow, to an inner rotating disc, to precession of the jet or to the lateral expansion of gas in a cocoon around the propagating radio jet. Indeed, in support to the latter explanation, the results from Fathi et al. (2011) and Couto et al. (2013) indicate that the radio jet impacts on the circumnuclear gas in the galaxy disc. Riffel et al. (2014Riffel et al. ( , 2015 observe strip-like enhanced velocity dispersion (resembling in shape what we observe in IC 5063 and NGC 1386) in NGC 5929 perpendicularly to the radio jet and to the bright emission-line lobes. The feature is found in both ionised gas from [Fe ii] and Paβ and warm molecular gas from H 2 . Even though the results from their work indicate an interaction of the jet with the gas in the disc, they ascribe the velocity width enhancement to an equatorial outflow from the accretion disc or the dusty torus, supported by the detection of weak extended 0.4 GHz radio emission approximately in the direction of velocity dispersion enhancement by Su et al. (1996), who attribute it to a flow of relativistic particles launched by the AGN perpendicularly to the main radio jet.
The phenomenon is observed also in NGC 2110, where a broadening of velocity dispersion is observed in an elongated area roughly perpendicular to the radio jet and emission-line axis, in both ionised gas from [O iii] and [N ii] (González Delgado et al. 2002, Schnorr-Müller et al. 2014) and warm molecular gas from H 2 (Diniz et al. 2015). They interpret it as due to gas in the disc disturbed by a nuclear outflow. Rosario et al. (2010) derive an inclination of 20 • between the jet and the galaxy disc plane in this object. Lena et al. (2015) observe with GMOS/IFU in the inner ∼7 of NGC 1386 the elongated enhanced velocity dispersion perpendicular to the small radio jet and AGN cones that we fully observe with MUSE on larger scales (∼20 ). They interpret it as possibly due to a wind which is both equatorially propagating away from the dusty AGN torus and rotating about the radiation cone axis. Schnorr-Müller et al. (2016) observe a band of enhanced velocity dispersion in [N ii] perpendicularly to the major axis of the ionised gas emission and to the direction of the bipolar ionised outflow in NGC 3081. There is tentative evidence for a jet from radio data (Mundell et al. 2009, Nagar et al. 1999, showing marginally resolved emission aligned with the ionised gas major axis (thus perpendicular to the velocity dispersion enhancement), though the radio data cannot confirm nor rule out the presence of a jet. Freitas et al. (2018) observe a line velocity width enhancement perpendicular to [O iii] lobes and radio jets in Mrk 79 and Mrk 607, interpreting it as either lateral expansion of the gas due to the passage of a radio jet and/or expansion of the dusty torus surrounding the nucleus. Riffel et al. (2013) mention that the cospatiality between the ionised bipolar lobes and the radio jet in Mrk 79 indicates an interaction of the jet with the ISM. Finlez et al. (2018) observe broad optical emission lines (especially [O iii]) in NGC 3393 in a thick band perpendicular to radio jet and optical ionisation axis, and interpret it as an accretion disc equatorial outflow as well. According to Finlez et al. (2018), the tight cospatiality between radio jet and emission-line lobes and the perpendicularity of the edge-on water maser (Kondratko et al. 2008) to both the jet and the almost face-on galaxy major axis indicate that the jet is launched into the disc of the galaxy.  Shimizu et al. (2019) mentioned above, they also find an enhancement in the velocity dispersion of CO(2-1) for the molecular gas in the same direction and scale as that in [O iii] but a factor of ∼ 6-8 smaller. According to Riffel et al. (2006), the jet is launched at small inclinations into the galaxy disc and impacts its ISM (also Falcke et al. 1996).
Summing up, all the above-mentioned galaxies show enhanced line velocity widths perpendicularly to their radio jets and ionisation cones/lobes. We stress that the mentioned galaxies also host a "normal" ionised outflow with high bulk velocity in the direction of the ionisation lobes and jets and that their jets are low-power ( 10 44 erg s −1 ) and small-scale, being extended on a few arcsec (i.e. 1 kpc). Moreover, most of them have in common a strong brightening of the optical line emission in cor-respondence to the radio jet hotspots, indicating an interaction between the radio jets and the ISM of the host galaxy.

Discussion on the origin of the phenomenon
All the systems studied in this work, together with those discussed in Sect. 4.1, show (compact) low-power radio jets propagating from their nuclei and enhanced gas velocity dispersions on scales of a few kpc in the direction perpendicular to the jet propagation. Based on the above discussion, we propose that the most likely origin for the observed phenomenon is the radio jet strongly interacting with the ISM in the galaxy disc during its propagation through it, releasing energy and giving rise to highly turbulent motions in the perpendicular direction. As mentioned earlier, the inclination angle of the jets with respect to the galaxy disc plane is low enough to allow strong interaction with the disc ISM, which seems evident even when the jet inclination is not derived. This scenario is further supported by the shock-like line ratios, associable to such turbulent material, detected in the same perpendicular direction (consistently with Mingozzi et al. 2019, in which the same MUSE observations were employed). The high [S ii]/Hα and [N ii]/Hα ratios observed there (up to values ∼0.2−0.3 in log, see BPT diagrams in Figs. 2c,d, 5c,d, 7c,d, 10c,d and in Mingozzi et al. 2019) are in fact reproduced by shock models (Allen et al. 2008) with shock velocities in the range 100−1000 km/s (details in Mingozzi et al. 2019). In addition, the spectrum of the extended X-ray emission from Chandra in the region of line width enhancement in NGC 1068 (the only target out of the four presented having enough X-ray statistics in such region) is also consistent with the presence of shocks. Moreover, as stressed before, objects in our MAGNUM survey which do host a jet (Centaurus A) or show indication of it (Circinus), but perpendicular to the galaxy disc, exhibit no line width enhancement perpendicularly to the jet or, at most, only on very small scales ( 20−40 pc in Centaurus A). This is consistent with a scenario in which jets launched perpendicularly to the galaxy disc have weak or no interaction with the disc ISM.
Indeed, simulations of jets propagating in a clumpy medium (as the ambient gas in galaxies is expected to be) indicate that the effects of jets on the ISM are extremely different depending on their power and on their inclination with respect to the galaxy disc (Wagner & Bicknell 2011, Mukherjee et al. 2017, 2018a. According to such simulations, jets launched perpendicularly to the disc will have in fact a very weak impact on the ISM of the galaxy, whereas jets directed at small inclinations (or even up to 45 • ) over the disc plane will strongly interact with the clumpy ISM and struggle to dig their way through it. Moreover, while high-power jets ( 10 45 erg s −1 ) will more easily penetrate through the disc due to their strong mechanical pressure and impact on it mainly in the proximity of their path, more dramatic jet-ISM interaction will occur in the case of low-power jets ( 10 44 erg s −1 ), as those hosted in the sources in exam. In this circumstance, the jet will propagate extremely slowly through the disc while, at the same time, widely perturbing its ISM in the direction perpendicular to propagation and giving rise to strong turbulence perpendicularly to the galaxy disc, along the direction of minor resistance (D. Mukherjee, priv. comm.). While it is unclear whether these simulations can reproduce in detail the observational features discussed in this work, they clearly highlight that low-power jets with low inclinations on the galaxy disc can strongly affect the host galaxy ISM.
We consider less likely other explanations alternative to the jet origin for the observed line velocity width enhancement, for the following reasons: (i) We exclude the possibility of beam smearing, since the scale on which we and other authors observe the line width enhancement is much larger than the spatial resolution of the observations. (ii) Some of the above works interpret the observed feature as due to an equatorial outflow, predicted by some models to originate from the BH accretion disc (e.g. Li et al. 2013) or from the dusty torus (e.g. Elitzur & Shlosman 2006, Mor et al. 2009, Elitzur 2012. We do not exclude that the line width enhancement observed in our sample and in the other mentioned cases might also be compatible with an outflow launched radially in the equatorial plane at the base of the jet with a certain opening angle. Projection effects may easily broaden the line profiles, producing the line width enhancement observed, although we note that a net blue-or redshifted velocity is only occasionally measured in the high velocity width regions. It is also possible that such an equatorial outflow may interact with the galaxy ISM, losing its speed while promoting turbulence within the disc. However, we suggest that even in this scenario an origin from a jet-ISM interaction producing such equatorial gas flow has to be preferred. In fact, the phenomenon of enhanced line velocity widths perpendicular to the AGN ionisation cones is observed, to our knowledge, exclusively in galaxies hosting a radio jet interacting with the disc, as discussed before. (iii) Finally, the multi-direction outflow scenario due to jet precession seems unlikely since in this case random outflow directions would be expected, while the observed features are systematically perpendicular. Moreover, we stress that the "canonical" outflow (with high bulk velocity) observed in the direction of the AGN ionisation cones and the material in the perpendicular direction show completely different kinematic properties pointing to a different origin of the two, the former being characterised by a coherent velocity field, the latter being instead dominated by velocity dispersion and not by a definite net velocity.
Based on all the above considerations we consider more likely the interaction of the jet propagating through the galaxy disc ISM to be responsible for the observed phenomenon. Unfortunately, the physical details on how the jet could give rise to the observed perpendicular enhanced emission line widths cannot be explained solely through the presented observational data and thus a complete description of this phenomenon goes beyond the scope of this work.
Finally, as mentioned, in some objects the enhanced perpendicular line velocity width is observed not only in the ionised gas, but also in the molecular one (Shimizu et al. 2019and Feruglio et al. 2020in CO, Riffel et al. 2015and Diniz et al. 2015, though with smaller values compared to the ionised phase (a factor 3-8 for CO and 2-3 for H 2 ). We might then speculate that the turbulence and perturbations induced perpendicularly by the radio jet in its propagation through the disc affect more strongly the ionised phase than the denser molecular one, though additional molecular gas observations are required to assess this issue.

Ionised mass affected by the phenomenon
We estimate the mass of ionised gas affected by the phenomenon of velocity width enhancement in the galaxies we presented. We employ Hα instead of [O iii] to obtain the mass since its luminosity does not depend on gas metallicity and on the energy of the ionising photons (e.g. Carniani et al. 2015). We extracted the integrated Hα modelled flux from our MUSE maps from the regions having an [O iii] W70 > 300 km/s (and a S/N > 3) and calculated its luminosity considering the corresponding distances reported in Table 2. We corrected the luminosity for extinction by employing a Calzetti et al. (2000) attenuation law for galactic diffuse ISM (R V = 3.12) and an intrinsic ratio (Hα/Hβ) 0 = 2.86 (for an electron temperature of T e = 10 4 K; Osterbrock & Ferland 2006). We finally calculated the mass of ionised gas through the following relation from Cresci et al. (2017), which assumes "Case B" recombination in fully ionised gas with electron temperature T e = 10 4 K: (1) The electron density n e was obtained from the [S ii] λ6716/λ6731 diagnostic line ratio (Osterbrock & Ferland 2006; still from the spaxels with [O iii] W70 > 300 km/s and S/N > 3 on the [S ii] lines), assuming a typical value for the temperature of ionised gas of T e = 10 4 K. Table 3 reports the mass of ionised gas that we find in the region of line width enhancement for the four galaxies we analysed in this work. The changes in extinction and electron densities across the considered regions are included in the respective uncertainties on these quantities. We note that the values we calculated may be considered as upper limits to the ionised gas mass which is actually affected by the jet perpendicular perturbation, since the flux extracted from the integrated line profile may include contributions from unperturbed gas or from gas partaking in the "standard" high-velocity outflow in the direction of the jet and ionisation cones. We add that other methods to infer the ionised gas density, such as that exploiting auroral and transauroral lines or the Baron & Netzer (2019) method based on the ionisation parameter, give higher electron densities, up to an order of magnitude, compared to the [S ii] doublet ratio method we employed (Davies et al. 2020). By using these alternative methods, the resulting masses would be up to an order of magnitude smaller compared to those we obtain. However, as indicated by the high [S ii]/Hα line ratios observed, the gas in the region perpendicular to the jet is characterised by low ionisation and the [S ii]-ratio method is likely tracing properly the ionised gas density. We also estimate the kinetic energy of the gas in the same region, M ion σ 2 ion /2, by employing the [O iii] velocity dispersion σ ion in the enhancement region. We note that the kinetic energy determined using the Hα line is marginally different (being its W70 not identical to that of [O iii], see Fig. A1 in Appendix), but still consistent with the uncertainties.
We compared the inferred masses and kinetic energies with the extension and power of the jet, to check for presence of any correlation. The jet power, when not found in literature, was calculated by employing Eq. 16 from Bîrzan et al. (2008), which relates the cavity (jet) power and the 1400 MHz radio luminosity of the source in objects showing cavities in their X-ray haloes filled by radio emission. For NGC 5643 we considered the radio power P 8.4 GHz ∼ 5.5 × 10 20 W Hz −1 given in Leipski et al. (2006) and for NGC 1386 the flux density S 8.4 GHz ∼ 10.3 mJy from Mundell et al. (2009) (corresponding to P 8.4 GHz ∼ 3.3 × 10 20 W Hz −1 at the distance of the galaxy). We assumed a power-law spectrum (∝ ν −α ) with α = 1 to rescale to the 1.4 GHz power involved in the Bîrzan et al. (2008) relation. For NGC 1068, we employed the value given by García-Burillo et al. (2014), who also employed the Bîrzan et al. (2008) relation. For consistency, we also calculate the jet power for IC 5063 by using the Bîrzan et al. (2008) relation, finding P jet ∼ 5 × 10 43 erg/s, though we note that higher values are reported by Morganti et al. (2015) (5−9 × 10 43 erg/s) and Mukherjee et al. (2018a) (between 10 44 and 10 45 erg/s), the latter from jet-ISM interaction simulations. As commented in Mukherjee et al. (2018a), the values obtained from simulations for IC 5063 are about an order of magnitude higher than Table 3: Ionised gas mass, kinetic energy, visual extinction and electron density in the region of enhanced line velocity width ([O iii] W70 > 300 km/s), as well as spatial extension of the W70 enhancement (total, not per side), for the four galaxies presented in this work, compared to their jets' length (total, not per side) and power.    Table 3. Note that the jet power resulting from simulations of jet-ISM interactions could be an order of magnitude higher than that reported, obtained from empirical relations (Bîrzan et al. 2008), based on the results from simulations in Mukherjee et al. (2018a) for IC 5063. those obtained from empirical relations (i.e. Bîrzan et al. 2008, Cavagnolo et al. 2010) between radio power and cavity power derived for classical evolved radio jets in haloes of galaxies or clusters, which may not apply to jets propagating into the ISM of a galactic disc. Based on this, we stress that, besides IC 5063, also the jet powers calculated for the other three galaxies, reported in Table 3 and Fig. 11, could be an order of magnitude higher when resulting from jet-ISM simulations.

Galaxy name
Despite the values reported in Table 3 can be considered only as indicative as pointed out above, we note that higher masses and kinetic energies of the ionised gas in the line width enhancement region are roughly associated with more powerful jets (Fig.  11), suggesting that more powerful jets are able to affect larger quantities of ISM and reinforcing the possibility that jets are responsible for the observed phenomenon. The same would hold also for the jet length, if we excluded NGC 5643 which exhibits a longer jet given its power compared to the other targets.
In order to infer whether the jet is energetic enough to power the observed features, we must compare the total kinetic energy, E jet , produced during its travelling time, t jet , with the kinetic energy of the material affected by the line width enhancement, M ion σ 2 ion /2. By assuming that the currently measured jet power P jet is representative for its mean value over its travelling time, we have E jet = P jet t jet . Mukherjee et al. (2018b) estimate a jet travelling time of ∼ 0.4 Myr for the case of IC 5063. By using Eq. A1 from Mukherjee et al. (2018b) and the same parameters they employed for IC 5063 6 , we can estimate the jet travelling time for the other remaining three objects in our sample. By considering the jet lengths given in Table 3 (divided by 2 to get the distance travelled by the jet per side), we obtain t jet ∼ 0.8, 0.3 and 0.03 Myr for NGC 5643, NGC 1068 and NGC 1386, respectively. We stress that different values from those adopted for IC 5063 for the quantities involved in the equation may apply to these other three objects.
By dividing the kinetic energy of the line width-enhanced perpendicular material, M ion σ 2 ion /2, by P jet t jet , we found values much smaller than 1, in the range 10 −4 -10 −2 . This indicates that the jets are easily capable, even with a low energy transfer efficiency, of injecting into the ISM the energy needed. An even lower efficiency would be needed in case the jet powers are one order of magnitude larger than those considered, which are derived from empirical relations, and/or if the [S ii]-ratio method employed underestimates the gas density (and thus overestimates its kinetic energy), as discussed before.

Conclusions
We presented flux, kinematics and excitation (BPT) maps of the ionised gas of the nearby Seyfert galaxies IC 5063, NGC 5643, NGC 1068 and NGC 1386 obtained with the optical and near-IR integral field spectrograph MUSE at VLT, as part of our MAG-NUM survey. All these galaxies host a low kinetic power ( 10 44 erg s −1 ) radio jet on scales 1 kpc aligned with the AGN ionisation cones axis, having low inclinations with respect to the galaxy disc (∼45 • at most) and showing evidence of interaction with the disc ISM. The results of the work are summarised in the following.
We find that the bulk of the high-velocity gas (in the range ±|200-1000| km/s) is directed as the jet and AGN ionisation cones, as expected for outflows in Seyfert galaxies. However, we detect a strong (up to W70 800−1000 km/s) and extended ( 1 kpc) emission-line velocity width enhancement perpendicularly to the direction of the AGN ionisation cones and jets, with fairly symmetric line profiles and without a coherent velocity shift on each side of the nucleus. Moreover, we find the excitation of the gas in such perpendicular region to be consistent with the presence of shocks, associable, together with the broadness of the line profiles, to turbulent gas. Other recent works observed the same peculiar phenomenon of enhanced line widths perpendicular to ionisation cones and jets, in nearby Seyferts which host low-power jets showing evidence of interaction with the galaxy disc ISM.
We consider the interaction between the jet and the galaxy disc, perturbing the disc material during the jet propagation through it, the most likely origin for the observed phenomenon. We favour this to alternative proposed interpretations, such as beam smearing, equatorial outflows from the accretion disc or the dusty torus and multi-direction outflows due to jet precession for the following reasons: -The perpendicular extended line velocity width enhancement is observed exclusively in galaxies hosting a (low-power) jet whose inclination happens to be low enough over the galaxy disc to have significant interaction with its ISM, as also indicated by recent simulations. This points to the jets as responsible for the observed phenomenon. -The scales on which the phenomenon occurs ( 1 kpc, i.e. several arcsec) are well resolved by MUSE, which excludes beam smearing. -The very broad line profiles might be compatible with an outflow launched in the equatorial plane with a wide angle, considering projection effects, although a high net blue-or redshifted velocity is only occasionally measured in the high velocity width regions. However, even in this case, we favour an origin from jet-ISM interaction producing such equatorial gas flow rather than from an accretion disc or torus wind. In fact, the phenomenon of enhanced line velocity widths perpendicular to the AGN ionisation cones is observed, to our knowledge, exclusively in galaxies hosting a radio jet interacting with the disc. -The observed enhanced line velocity widths are systematically (roughly) perpendicular to the high-velocity ionisationcone outflow, which excludes the multi-direction outflow scenario caused by jet precession, since random outflow directions would be expected in this case. Furthermore, the different kinematic properties of the gas in the two directions, that is, broad and symmetric in one case and narrower, asymmetric and with a spatially-coherent velocity in the other, also disfavours such common origin.
Finally, we find that the jets are powerful enough to provide the kinetic energy of the ionised gas observed in the line width enhancement region and that higher masses and kinetic energies of the line width enhanced gas tend to be associated to more powerful jets. However, a larger sample with high-quality (MUSE-like) integral field spectroscopic data would be needed to identify more sources showing the phenomenon and better investigate such trends. A similar study focused on molecular gas would also be needed to assess at which extent the phenomenon affects the molecular phase, given that a few mentioned works find enhanced line velocity widths even in H 2 and CO perpendicularly to AGN ionisation cones and jets.