Seyfert galaxy NGC 7172. From top to bottom: Panel a: HST optical to near-IR composite RGB image of NGC 7172 retrieved from ESASky4.3.0. It combines observations from the Advanced Camera for Surveys (ACS) at 6060 and 8140 Å, and the Wide Field Camera 3 (WFC3) at 1.6 µm. The orientation of the image is north up, east to the left. The FoV is 2 × 2 . The rectangle shows approximately the ALMA FoV, while the dashed lines represent the opening angle of the southern (brighter) side of the optical ionization cone. Image credit: ESA/Hubble & NASA, D. J. Rosario, A. Barth. Panel b: ALMA CO(3−2) intensity map (moment 0) produced with a 3σ clipping using the merged configuration observations. We trimmed the original FoV to approximately 17.6 × 3.3 . Both the image and the contours are shown on a linear scale. The color bar shows the intensity scale in Jy km s −1 per beam units. The first contour is at 0.05 Jy km s −1 per beam. The ALMA beam (not shown) is 0.08 × 0.07 (14 pc × 13 pc) at PA beam = 90.4 • . Panel c: ALMA CO(3−2) mean velocity map (moment 1) produced with a 3σ clipping using the merged configuration observations. The contours are the isovelocities. Panel d: ALMA CO(3−2) mean velocity dispersion map (moment 2) produced with a 3σ clipping using the merged configuration observations. For the last two panels the scale bar units are km s −1 .

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... is also a broader dust lane extending east-west across the galaxy that appears to be warped at the edges ( Sharples et al. 1984). Figure 1 (top panel) shows a red-greenblue (RGB) optical to near-IR Hubble Space Telescope (HST) image of NGC 7172 retrieved from ESASky ( Baines et al. 2017;Giordano et al. 2018), where this morphology is clearly seen. The distribution of the prominent dust lanes to the north of the nucleus indicates this is the near side of the galaxy. ...

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... Thomas et al. (2017) detected a prominent two-sided ionization cone in NGC 7172 using optical integral field unit (IFU) spectroscopy. It has a projected opening angle of approximately 120 • . The southern part of the cone is brighter, which is consistent with the position of the main dust lane and with north being the near side of the galaxy (see Fig. 1, top panel). The size on this side of the cone is approximately 5 , which is equivalent to a projected physical size of 900 pc. Using spectroscopic observations with X-shooter on the Very Large Telescope (VLT), Davies et al. (2020) derived a velocity for the ionized gas outflow of ∼400 km s −1 and an outflow rate of 0.005 M yr −1 . In ...

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... sensitivities in the line data cubes were derived by selecting areas free from emission in all channels. We summarize in Table 1 all the relevant parameters of the ALMA observations. We created CO(3−2) moment maps from the merged configuration data set using the GILDAS moment task with a 3σ clipping. We show the 0th, 1st, and 2nd moment maps in Fig. 1, while Fig. 2 show the 854 µm continuum maps of the central region observed with the compact and merged configurations. Additionally, in Sect. 4 we discuss the moment maps from the compact ...

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... ALMA CO(3−2) and 854 µm emission Figure 1 (second panel from the top) shows the ALMA CO(3−2) intensity map (moment 0) derived from the merged configuration data set. It maximizes the best angular resolution with the best sensitivity of our observations. ...

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... of 6−8 or 1.1−1.4 kpc, containing bright clumps. Beyond the ring, the CO(3−2) emission becomes more diffuse and covers the ALMA FoV along the east-west direction. The presence of this ring was already suspected from previous ALMA CO(2−1) images at lower angular resolution (see Alonso-Herrero et al. 2020). For a scale reference, the top panel of Fig. 1 displays the approximate FoV of the ALMA CO(3−2) image plotted as a red rectangle. The CO(3−2) emission clearly traces the prominent dust lane that crosses the (circum)nuclear region of the galaxy. In the innermost 4 , the CO(3−2) emission delineates the extinction in the ring derived from the VLT/SINFONI near-IR continuum and the ...

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... map of the CO(3−2) mean velocity (see Fig. 1, third panel from the top) from the merged configuration shows a rotation pattern. There are also clear distorsions in the velocity field, which might be in part due to the presence of an ILR in NGC 7172. However the clear departure from rotation in central region along the minor axis of the galaxy are indicative of the presence of ...

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... the presence of an ILR in NGC 7172. However the clear departure from rotation in central region along the minor axis of the galaxy are indicative of the presence of radial motions. In Sect. 4, we perform a detailed modeling of the CO(3−2) kinematics and quantify the velocity and sign of these radial motions. The mean velocity dispersion map (see Fig. 1, bottom panel) shows a complex structure with several regions with velocity dispersions above 100 km s −1 , H 2 ...

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... (p−v) diagrams along the kinematic major and minor axes. Before we started the fits, we trimmed the original compact configuration data cube to the FoV with detected emission, ∼20.9 × 4.6 . Figure 6 shows the ALMA CO(3−2) observed moment maps of NGC 7172. The intensity, velocity, and velocity dispersion maps are similar to those in Fig. 1, considering the difference in angular resolution. The CO(3−2) mean velocity field shows a general rotation pattern. However, some important distorsions are readily seen in the molecular gas ring, which are accompanied by the presence of high velocity dispersion values, especially along the east-west direction in the disk of the ...

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... the approximate inner 2 , the minor axis p−v diagram shows redshifted motions to the south of the AGN and blueshifted to the north (see Fig. 8, bottom panel). Since the north is the near side of the galaxy (see the top panel of Fig. 1), this suggests the presence of an outflow in the cold molecular gas ring, if these motions are taking place in the plane of the galaxy. We thus run another 3D BAROLO model including a radial velocity (v rad ) component. We fixed the inclination to the average value from the previous run and the derived systemic velocity. We also fixed ...

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... Fig. 9 (top and bottom panels, respectively). It is immediately clear from the comparison with Fig. 7, that the 3D BAROLO model with the fixed rotation curve and the radial velocity component produces a better fit to the observations. The effect of including the latter is appreciated in the CO(3−2) p−v diagram along the kinematic minor axis (see Fig. 10). However, even when including radial velocities, the model does not reach the observed velocity of nearly +150 km s −1 to the south, close to the AGN position. The maximum fitted radial velocities are 80−100 km s −1 (see the bottom panel of Fig. 11), progressively decreasing to 20−30 km s −1 out to a radial distance of 4.5 . This ...

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... including the latter is appreciated in the CO(3−2) p−v diagram along the kinematic minor axis (see Fig. 10). However, even when including radial velocities, the model does not reach the observed velocity of nearly +150 km s −1 to the south, close to the AGN position. The maximum fitted radial velocities are 80−100 km s −1 (see the bottom panel of Fig. 11), progressively decreasing to 20−30 km s −1 out to a radial distance of 4.5 . This deceleration might be due to the AGN wind encountering large amounts of molecular gas. The bright peaks of H 2 , CO(3−2), and 854 µm emission in the ring (see Sect. 3) might be caused by this impact. Within the gas ring, the gas velocity dispersion takes ...

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... wind encountering large amounts of molecular gas. The bright peaks of H 2 , CO(3−2), and 854 µm emission in the ring (see Sect. 3) might be caused by this impact. Within the gas ring, the gas velocity dispersion takes values of approximately σ gas 10 km s −1 , except in the region with the largest radial velocity values (see the middle panel of Fig. 11) where the gas dispersion is slightly lower. At r > 4.5 , the velocity dispersion goes down to the minimum value imposed in our fit (σ gas = 5 km s −1 ...

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... the northeast. They appear to be coincident with those regions where the innermost part of AGN wind, traced by the VLT/SINFONI [Si vi] emission (see left panels of Fig. 4), impacts the inner part of the cold molecular gas ring. Even though at the radial distances of these regions we fit the largest values of the radial velocities (bottom panel of Fig. 11), the residuals mean that this azimuthally averaged model cannot explain completely the observed kinematics. In fact, these distinct velocity residuals also define kinematically the expanding molecular ring with a diameter of ∼6 or approximately 1.1 kpc. The residual mean velocities are not only confined to these regions, but there are ...

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... left panels of Fig. 12 show the observed 854 µm continuum of the central 0.4 × 0.4 (approximately 72 pc × 72 pc) for the observations with the highest angular resolution (extended configuration, top panel) and the intermediate resolution (merged configuration, bottom panel). The corresponding physical resolutions are approximately 11 pc and 13 pc, ...

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... to the synchrotron emission. Briefly, we started by fitting the extended configuration 854 µm continuum map with a point source with the observation beam size and orientation, and an elliptical component. The estimated unresolved flux is 520 µJy. We then subtracted the point-source fit from the observations. The point-source subtracted image (Fig. 12, top-right panel) shows no emission residuals at the AGN position, that is, all the observed emission at this angular resolution is unresolved. Next, we generated a point source image corresponding to the beam of the merged configuration data set, scaled it to the point source flux from the previous step, and subtracted it from the ...

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... corresponding to the beam of the merged configuration data set, scaled it to the point source flux from the previous step, and subtracted it from the observations. The 854 µm point source subtracted image shows significant extended emission at the 3 to 5 × σ levels, whereas at the AGN position there is no residual emission (bottomright panel of Fig. 12). The measured fluxes are 877 µJy for the point + extended emission and 364 µJy after the point source subtraction. The extended emission therefore accounts for approximately 42% of the observed flux within r = 32 pc and Notes. We used different brightness temperature ratios for the torus and the other regions, namely, T B CO ( can be ...

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... value estimated from the cold dust emission. It is also within the range of torus masses inferred in other Seyfert galaxies ( García-Burillo et al. 2021). We measured an H 2 column density at the AGN position of log (N H2 ) = 22.34 mol cm −2 , which agrees well the observed values in other GATOS Seyfert galaxies with similar AGN luminosities (see Fig. 19, right, from García-Burillo et al. ...

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... Sect. 4.2, we showed that the CO(3−2) minor axis p−v diagram (Fig. 10) goes across significantly strong emission from the ring. Under the commonly assumed hypothesis that the bulk of molecular gas shares a coplanar geometry, the v rad term is the only component of gas motions that has a nonzero projection along the disk minor axis. If the molecular gas is following circular orbits, for the known ...

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... absorption feature. They measured an approximate blueshifted velocity of 50 km s −1 of the OH feature, which the authors considered just at the limit of their outflow detection criterion. This value of the OH velocity is similar to the typical value of the CO(3−2) radial velocity fit with 3D BAROLO in the molecular gas ring (see bottom panel of Fig. 11). In the particular case of NGC 7172, the detection of the OH outflow was probably aided by the fact that the outflow is observed close to our line of ...

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... quantity explaining the different gas phases of outflows in active galaxies ( Fluetsch et al. 2019;Davies et al. 2020). On the other hand, our results indicate that NGC 7172 follows well the trend between L AGN and molecular gas mass outflow rate found by Lutz et al. (2020) for a compilation of local infrared bright galaxies, gray points in Fig. 13. We note however that other works, such as Ramos and Lamperti et al. (2022), do not find tight correlations between these quantities for samples of type 2 quasars (QSO2s) and local ULIRGs classified as AGNs, red triangles and orange squares, respectively. In simulations of AGN winds in disk galaxies, the outflows are predicted to ...

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... vi] emission (Sect. 3 and Figs. 2 and 4) add support to this scenario. At this particular location of the NGC 7172 ring (also on the other side, to the northeast of the AGN), it is likely that the impact with material in the ring caused a strong deceleration of the AGN wind and subsequently in the outflow velocity of the molecular gas, as seen in Fig. 11 (bottom panel). Indeed, in Davies et al. (2020) sample, NGC 7172 is among the Seyfert galaxies with the lowest velocities of the ionized gas, thus providing further evidence to the above ...

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... r = 200 pc scale does not encompass the entire ring at all. Increasing the size of the circumnuclear region to include the ring gives a concentration index of log Σ r=50 pc H2 /Σ r=720 pc H2 = −0.6. The comparison of the two molecular gas concentration indices of NGC 7172 with the sample of low-luminosity AGNs and GATOS Seyfert galaxies (Fig. 18 of García-Burillo et al. 2021) indicates that NGC 7172 follows well the observed trends for the two physical scales of the torus and its immediate surroundings. That is, there is a redistribution of the molecular gas in the torus and nuclear regions of NGC 7172 when compared to other less luminous Seyfert galaxies and AGNs. For this ...

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... finally explore the fate of the circumnuclear molecular gas in NGC 7172 since its mass outflow rate appears to be at the high end of those observed in other AGNs of similar luminosity (Fig. 13). On the other hand, the velocity of the molecular outflow of NGC 7172 is modest when compared with the galaxy circular velocity. In Appendix B we modeled the escape velocity in NGC 7172 using the 3D BAROLO rotation curve. At a radial distance of 900 pc, just outside of the outflow region, the escape velocity is 850 km s −1 , whereas at ...

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... outflow of NGC 7172 is modest when compared with the galaxy circular velocity. In Appendix B we modeled the escape velocity in NGC 7172 using the 3D BAROLO rotation curve. At a radial distance of 900 pc, just outside of the outflow region, the escape velocity is 850 km s −1 , whereas at smaller radial distances this velocity is even higher (see Fig. B.1). Given that the molecular outflow is taking place mostly in the disk of the galaxy and its velocity is low with respect to the expected escape velocity, we can therefore conclude that in this galaxy most of the molecular gas will not leave the galaxy, at least during this period of AGN ...

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... appendix describes a bar-ring model, with the nuclear bar being the source of noncircular motions in the center, as an alternative explanation for the observed CO(3-2) kinematics of the central regions of NGC 7172. The central gas distribution mapped with ALMA has an extent of 3.2 kpc or projected radius of 1.6 kpc (c.f., Fig. 1). Its morphology reveals a central ring, with the characteristic enhancement in the northeast and southwest parts of the ring, as shown in Fig. 2. This indicates that the ring may be a pseudo-ring, made by the winding of the two spiral arms, elongated along the bar, and usually observed as the dusty leading edges of the bar in spiral ...

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... ring is ∼300 pc, typical of an ILR. This central molecular feature appears very elongated. It is likely however that the ring and barred structure are intrinsically elongated, considering that the inclination of the galaxy is not completely edge-on, but of the order of ∼60 • , as noted by Hyperleda and the observed large-scale optical morphology (Fig. 1). We then assumed this value of the inclination in the following modelization. We used N-body simulations with gas, star formation, and feedback, as described in Combes (2008). The Poisson equation is solved with a 3D Particle-Mesh code based on FFT, and is fully self-consistent with a live dark halo. The gas dissipation is represented ...

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... several components, including a stellar bulge and disk, a dark matter halo, and a gas disk, with the parameters listed in Table A.1. The shape of these components are Miyamoto-Nagai disks and Plummer spheres, as described in Chilingarian et al. (2010). The computed circular velocity and angular frequencies, Ω, Ω ± κ/2, Ω − κ/4, are plotted in Fig. ...