Spatially Resolved Ionized Outflows Extending to ∼ 2 kpc in Seyfert 1 Galaxy NGC 7469 Revealed by the Very Large Telescope/MUSE

The MUSE (Bacon et al. 2010) is an IFS located at the Very Large Telescope (VLT) of the European Southern Observatory (ESO). In the wide field mode (WFM), MUSE provides a large field of view (FOV) of nearly 1 arcmin² with spatial sampling of 02 pixel⁻¹, and a wavelength coverage of 4650–9300 Å with a mean resolution of R ∼3000. NGC 7469 was observed in WFM-NOAO mode on 2014 August 19 during the science verification run with an exposure time of 2.4 ks and mean seeing of 123 (see also Galbany et al. 2016; Robleto-Orús et al. 2021).

We downloaded the processed data from the ESO Archive Science Portal ¹ and fitted the data cube using the LZIFU pipeline (Ho et al. 2016), which is an IDL toolkit including the penalized pixel-fitting method (PPXF; Cappellari & Emsellem 2004) and the MPFIT routine that performs Levenberg–Marquardt least-squares minimization (Markwardt 2009). To cover the main emission lines in the optical band, for example, Hβ, [O iii]λ λ 4959,5007, Hα, [N ii]λ λ 6548,6583, and [S ii]λ λ 6716,6731, a fitting range of 4770–7550 Å was set. The redshift z = 0.01632 measured by Keel (1996) is used to correct the observed wavelength to the rest frame. Spaxels with mean S/N ≤ 1 (calculated from the spectrum between 5000 and 7000 Å) were excluded. We rebinned the remaining spaxels using the Voronoi binning method (Cappellari & Copin 2003) to achieve an S/N threshold of 25. The [O iii] emission lines show apparent blue asymmetry in the line profile, which is indicative of ionized gas outflow. The Balmer emission lines also present asymmetric profiles but are weaker than the [O iii], which is more likely dominated by rotation of the gas disk (also noted by Robleto-Orús et al. 2021). Such features in kinematics are common in nearby AGN hosts (e.g., Karouzos et al. 2016). When fitting Hβ, [O iii], Hα, and [N ii], two Gaussian components were used in the whole FOV for asymmetric line profiles. Note that the [O iii] doublets were fitted independently, and when fitting Hβ, Hα, and [N ii] emission lines, their center wavelength and velocity dispersion σ for the same component share the same value. Because [N ii]λ λ 6548, 6583 are strongly blended with Hα, it is reasonable to fix their velocity and σ with the same values of Balmer emission lines. Two components of emission lines were sorted using σ, i.e., the one with smaller σ was component one (the narrow component) and the one with larger σ was component two (the broad component). The [S ii]λ λ 6716,6731 doublets show a very weak asymmetric line profile, and only one Gaussian component is used to fit them for estimating the electron density. Figure 1 shows one example of the spectra and models. The broad component of [O iii] evidently shows larger wavelength shifts compared with other lines.

Zoom In Zoom Out Reset image size

In this work, we focus on the larger scale ionized gas of NGC 7469 with a FOV of ∼14″ × 14″ than Robleto-Orús et al. (2021) with a FOV of ∼5″ × 5″. To improve robustness of our results, we rejected components and spaxels with S/N < 5 for all fitted emission lines.

To correct the extinction effect, the Balmer decrement (the flux ratio of Hα and Hβ) was used. The attenuation law from Fitzpatrick (1999) with R_V = 3.12 and an intrinsic Balmer decrement Hα/Hβ = 2.86 (Osterbrock & Ferland 2006) were adopted for galactic diffuse ISM.

A nonparametric method is applied to characterize the line width and the velocity of emission lines within each spaxel for MUSE data following Harrison et al. (2014). For simplicity, the synthetic model with two Gaussian components (fitted by LZIFU) of each emission line was used instead of the data to provide the kinematics. As shown in Figure 2, we use W₈₀ = v₉₀ − v₁₀ and Δv = (v₉₀ + v₁₀)/2 to represent the line width and the velocity offset of the emission line model, where v₁₀ and v₉₀ are the velocities at the 10th and 90th percentiles.

Zoom In Zoom Out Reset image size

NGC 7469 was observed with ACIS-S with HETG on board the Chandra X-ray Observatory for 10 times from 2002 to 2016. Previously diffuse soft X-ray emission in NGC 7469 has been found by Mehdipour et al. (2018) using the Chandra observation with longest exposure (79ks, Obs. ID: 2956). We obtained all available Chandra observations of NGC 7469 from the Chandra Data Archive, ² reprocessed and merged them using CIAO 4.13 (Fruscione et al. 2006) with CALDB version 4.9.4. The total exposure time is 384 ks. We use this data set to compare the diffuse soft X-ray emission (here denotes the 0.2–1.0 keV band with the optical integral field unit (IFU) data). In Figure 11 of Mehdipour et al. (2018), the observation brightness profile shows an excess than the point-spread function (PSF). Following Mehdipour et al. (2018), a PSF for the X-ray image is simulated using Chandra Ray Tracer (ChaRT; Carter et al. 2003) and MARX (Davis et al. 2012). A PSF model representing the bright nucleus of NGC 7469 is subtracted from the merged data. The smoothed soft X-ray zeroth-order image with the PSF model subtracted is shown in Figure 3.

Zoom In Zoom Out Reset image size

The flux maps of Hα from the MUSE data are shown in Figure 4. In the narrow component flux map of Hα (Figure 4(b)), bright clumpy ionized gas emissions can be found around the nuclear starburst ring, and the spiral arms appear outside the ring. The broad component of Hα shows a bright nucleus (Figure 4(c)), which is expected given that the line emission is severely contaminated by the broad line region (BLR). Several clumps of Hα are clearly present along the starburst ring, likely associated with the giant H ii complexes. The [O iii] flux maps (Figure 5) show no clumpy or spiral features. This may indicate that the [O iii] emission is mainly originated from the nonrotational gas instead of the disk.

Zoom In Zoom Out Reset image size

Zoom In Zoom Out Reset image size

In Figures 4(a) and 5(a), soft X-ray contours are superimposed on the total flux maps of Hα and [O iii]. To quantify the asymmetry of these flux maps, the surface brightness (normalized to the mean value) of different bands in the labeled regions (see Figures 3, 4(a), and 5(a)) are shown in Figure 6. Because the nuclear region ( ≤14) is strongly affected by the BLR and we mostly focus on the extended emission on a larger scale, this central region is excluded here. In general, the soft X-ray, Hα, and [O iii] emissions present an asymmetric distribution along the northwest to southeast and the soft X-ray shows less asymmetry than the two optical emission lines in three panels. As for the Hα emission, it tends to be more asymmetric along the east to the west than the soft X-ray and [O iii], which can be seen from the enhancement in the west regions (A1, O1, A2, O2, and A3) and the deficiency in the east regions (A5, O5, A6, O6, A7, and O7). The asymmetry features of the soft X-ray emission around and outside the nuclear region are more consistent with the [O iii] emission than Hα.

Zoom In Zoom Out Reset image size

The kinematics maps of Hα ionized gas are shown in Figure 7. Note that Hα, Hβ, and [N ii]λ λ 6548,6583 were fitted with the same velocity and velocity dispersion. For simplicity, the kinematics maps of Hα in fact represent the kinematics for these emission lines. Because the kinematics of [S ii]λ λ 6716,6731 (fitted with a single component) are very similar to the narrow component of Hα, we do not present the velocity and velocity dispersion maps of [S ii]λ λ 6716,6731 here.

Zoom In Zoom Out Reset image size

The narrow component of Hα is dominated by the ionized gas disk due to the rotational pattern shown by the velocity and velocity dispersion maps (Figures 7(a) and 7(b)). We verified that the stellar kinematics are very similar to that of the narrow component of Hα by fitting the stellar continuum in individual spaxels. Previous studies have also established that the kinematics maps of the narrow component of Hα are dominated by the gravitational potential of a galaxy (e.g., Karouzos et al. 2016). For the broad component, complex patterns are present in the kinematics maps of Hα (Figure 7(c)). For [O iii] the velocity map (Figure 8) of the narrow component cannot be solely explained by a rotating gas disk. However, the velocity map of [O iii] shows mostly blueshifted features across the FOV. Comparing narrow and broad components of Hα and [O iii], the corresponding relationships between them cannot be directly obtained. A possible reason is that [O iii] doublet and Balmer emission lines are dominated by different ionized gas components. Balmer emission lines are sensitive to rotational disk and low-velocity ionized outflows, while [O iii] traces the narrow line region (NLR) and relatively high-velocity ionized outflows. To compare and quantify the kinematics of Balmer emission lines and [O iii] simultaneously, the nonparametric kinematics maps are further analyzed.

Zoom In Zoom Out Reset image size

Figures 9 and 10 show the nonparametric kinematics maps of Hα and [O iii], respectively. Note that the nuclear region ( <1.4″) is excluded in three panels (Δv_Hα , W80_{H α} , and Δv_Hα − v_Hα,peak) due to the contamination from the bright BLR. The v_peak maps of Hα and [O iii] appear similar to their velocity maps of the narrow component, hence we do not show them here. Theoretically, the velocity offset Δv is affected by two physical components: a rotational gas disk and nonrotational gas component. If an emission line is dominated by a rotational component and can be fitted with a single Gaussian model well, the velocity offset Δv will be equal to the v_peak and reflect the rotational velocity. When there exists another component (i.e., a nonrotational component), an extra velocity offset from this component will be included in the Δv. For example, the Δv_Hα map (Figure 9(a)) shows a rotational feature along the northwest to the southeast, whereas this feature disappears in the Δv_Hα − v_Hα,peak map (Figure 9(c)). Therefore, the Δv_Hα − v_Hα,peak map can represent the velocity offsets originated from the nonrotational gas component.

Zoom In Zoom Out Reset image size

The Δv_Hα − v_Hα,peak map shows complex and intriguing patterns. As the v_Hα,peak map is dominated by the rotational disk, this residual implies significant presence of the nonrotational component. In the Δv_Hα − v_Hα,peak map, there is a remarkable redshifted structure extending from the A7 region to the O7. In the corresponding regions of the W80_{H α} map, a high value of W80 is suggestive that this redshifted feature is an inflow-like structure. Another distinct feature in this map is located at the southeast corner of the FOV (O5 and O6 regions) with redshifted velocity and a high W80 value, which may also resemble an inflowing gas stream. In addition, the southeast redshifted structure appears in contact with a blueshifted feature in the O6 region. The presence of a Hα outflow is evident as shown in the A1, A2, O2, A3, and O3 regions, with significantly blueshifted emission (Δv_Hα − v_Hα,peak). In the corresponding regions of the W80_{H α} map, relatively high values of W80 are also consistent with an outflow feature.

Zoom In Zoom Out Reset image size

Zoom In Zoom Out Reset image size

As for the [O iii] maps (Figure 10), the Δv_{[O III]} map shows mostly blueshifted velocity offsets across the FOV. The Δv_{[O III]} − v_{[O III],peak} and the Δv_{[O III]} − v_Hα,peak maps are shown in Figures 10(c) and 10(e). The former presents less blueshift than the later especially in the A1, A2, A3, and A8 regions. The v_{[O III],peak} map cannot be explained only by the rotational ionized gas disk, with an excess of significant blueshifted velocity especially in the A1, A2, A3, and A8 regions (Figure 10(d)), which indicates in these regions the nonrotational component is more significant. Because the v_Hα,peak map closely resembles a rotational disk than v_{[O III],peak}, we use Δv_{[O III]} −v_Hα,peak to represent the ionized gas outflow component traced by [O iii]. After subtracting the rotational component (v_Hα,peak) from the Δv_{[O III]} map, the remaining shows blueshifted velocity offsets across the FOV (Figure 10(e)), especially in the western regions around the starburst ring (A1, A2, A3) and the regions outside the ring (O1–O8). The W80_{O III} map (Figure 10(b)) also shows good correspondence with the Δv_{[O III]} − v_Hα,peak map, indicating the Δv_{[O III]} − v_Hα,peak map is dominated by ionized gas outflows.

Both AGNs and starbursts can drive galactic ionized winds, and consequently it is difficult to determine the powering source. The Baldwin, Phillips, and Telervich (BPT) diagnostic diagram (Baldwin et al. 1981) is often adopted to distinguish ionization and excitation mechanisms of ionized gas with similar kinematics. Generally it is assumed that the ionizing source of the gas also drives the outflow, so the BPT diagram of ionized gas with similar kinematics is a popular diagnostic tool.

In Figures 7 and 8, our results show that the kinematics of [O iii] and Hα are inconsistent for both the narrow and the broad components, which suggests that the BPT diagram with the two components cannot be used directly. Previous work by Robleto-Orús et al. (2021) derived the BPT diagram for the narrow component, and cautioned that the blueshifted component of [O iii] and Hβ have inconsistent kinematics for many spaxels ( <25).

To obtain the BPT diagnostic diagrams for the rotational disk and the outflow components, two intervals in the line profile are invoked: the “narrow peak” and the “blue wing”. As illustrated in Figure 11, the “narrow peak” is the portion of emission line with velocity v_Hα,peak − 100 < v < v_Hα,peak + 100km s⁻¹, which should be dominated by the rotational disk (see the v_Hα,peak map in Figure 9). The “blue wing” is part of the line wing with v < −400 km s⁻¹, which is dominated by emission from the outflow component (see the Δv_{[O III]} −v_Hα,peak map in Figure 10). Such kinematically resolved BPT diagrams and maps have been demonstrated as useful by previous works (e.g., Mingozzi et al. 2019).

Figures 12(a) and 12(b) show the BPT diagnostic diagram and the corresponding ionization map of the “narrow peak” emission, respectively. Due to the exclusion of the nuclear region ( <14), the low ionization emission line region (LIER) is used instead of the low ionization nuclear emission line region (LINER) in this work. The “narrow peak” BPT diagram (Figure 12(a)) shows a concentrated distribution in the composite region extending to the Seyfert/LIER and the star-forming region, which is expected given the coexistence of starbursts and AGNs in NGC 7469. A patchy spiral arm structure classified as H ii (star formation) ionization can be found in the “narrow peak” BPT map, which is consistent with the spiral arm structure in the flux map of Hα (Figure 4). An intriguing arc structure mainly classified as LIER is also apparent in the southeast quadrant of the “narrow peak” BPT map, ∼ 2″–6″ away from the nucleus. A similar arc structure classified as LIER is also present in the “blue wing” BPT map, corresponding to the same area but slightly further away from the nucleus. According to previous work, such extended LIER regions could be associated with shocks produced by a jet or an outflow (e.g., Ho et al. 2014). Some studies also suggested that LI(N)ER can usually be found along the wall of conical outflow in an AGN (e.g., Maksym et al. 2016; Mingozzi et al. 2019). The emission from the outflow can also contribute to the “narrow peak” due to low line-of-sight velocity clouds in the outflow. We speculate that the arc structures in the “narrow peak” and “blue wing” BPT map could be associated with the edge of the kiloparsec-scale ionization cone, which is affected by shocks produced by the outflow. Based on the morphology, we can estimate the projected outflow size of ∼2kpc.

Zoom In Zoom Out Reset image size

Figures 12(c) and 12(d) show the BPT diagnostic diagram and map of the “blue wing” emission. The “blue wing” BPT diagram shows two domains of significantly clustered spaxels, one is the H ii region and the other is the Seyfert/LIER region. Figure 12(d) shows that most spaxels beyond the starburst ring are classified as an AGN ionized region, which suggests that the outflow beyond the starburst ring is mainly powered by the central AGN. The regions around the starburst ring and extending to the northeast are dominated by H ii ionization, which indicates the outflows in these regions are likely driven by a starburst. This is consistent with the strong star-forming activities in the ring and the findings of Robleto-Orús et al. (2021).

The ionized gas outflow mass can be estimated following Osterbrock & Ferland (2006), which assumes the “case B” recombination with electron temperature T_e = 10⁴K:

where L_Hβ is the luminosity of Hβ, n_e is the electron density, which can be calculated from the ratio [S ii]λ6716/[S ii]λ6731. Assuming the electron temperature T_e = 10⁴ K, the mean electron density across the FOV is estimated to be n_e ∼ 380 cm⁻³. The mass, energy, and momentum outflow rate are calculated following:

where v_out denotes the averaged velocity of the outflow, and R_out is the outflow size.

According to the kinematics maps of Hα, the nonrotational component cannot fully represent the outflow. Consequently, the broad component of Hβ cannot be directly used to estimate the total mass of the outflowing ionized gas. The Hβ flux associated with the outflow component (F_Hβ,OF) can be estimated following:

where F denotes the flux, the subscripts [O iii] and Hβ represent different emission lines, and the subscripts R, OF, and tot denote the rotational component, outflow component, and total flux, respectively. The total luminosity of Hβ and [O iii] associated with the outflow component can be estimated to be L_Hβ,OF =7.6 × 10⁴¹erg s⁻¹ and L_{[O III],OF} = 8.2 × 10⁴¹erg s⁻¹.

In NGC 7469, both the nuclear starburst ring and the AGN are the powering source responsible for the total mass and energy outflow rates. To estimate the outflow rates, we assume that the outflows in spaxels classified as H ii in the BPT diagram are driven by starbursts, and the outflows in other spaxels are driven by AGNs (see Figure 12(d)). Robleto-Orús et al. (2021) suggest that most of the ionized outflows in the circumnuclear region (r < 25) are possibly driven by starbursts. We use the mean value of [O iii]/Hβ of those pixels classified as H ii in the BPT diagram as the [O iii]/Hβ ratio of the masked nuclear region (r < 14).

The luminosity of Hβ associated with the starburst wind is estimated at L_Hβ,SB = 4.8 × 10⁴¹ erg s⁻¹ according to Equation (5) and as an assumption of the biconical outflow geometry. The luminosity of Hβ produced by the AGN outflow is L_Hβ,AGN =L_Hβ,tot − L_Hβ,SB = 2.8 × 10⁴¹ erg s⁻¹. Note that L_Hβ,SB can be overestimated under our assumptions due to ignoring the AGN contribution in the masked region. For simplicity, the sizes of the starburst wind and the AGN outflow are both assumed to be R_out ∼ 2 kpc. The average v₁₀ ∼ −510 km s⁻¹ and electron density n_e ∼ 380 cm⁻³ across the FOV are used to estimate the outflow rates. Based on Equations (1)–(4), the mass, energy, and momentum outflow rate of the starburst wind and the AGN outflow are estimated and summarized in Table 1. Outflow rates from starbursts are larger than the ones from AGNs, implying that starburst-driven outflows are more powerful than AGN-driven outflows in NGC 7469. Nevertheless, the AGN-driven outflows are also nonnegligible, carrying >30% of the total outflow mass and energy rates.

Table 1. Properties of Ionized Outflowing Gas

	L[O III]	LHβ				Fraction
Source	(× 1041erg s−1)	(× 1041erg s−1)	(M⊙ yr−1)	(× 1041erg s−1)	(× 1034g cm s−2)	(%)
(1)	(2)	(3)	(4)	(5)	(6)	(7)
Starburst	4.6	4.8	6.8	5.5	2.2	63.3
AGN	3.6	2.8	3.9	3.2	1.3	36.7
Total	8.2	7.6	10.7	8.7	3.5	⋯

Note. (1) Ionization source of the outflowing gas. (2) Luminosity of [O iii] associated with the outflow. (3) Luminosity of Hβ associated with the outflow. (4) Mass outflow rate with unit of M_⊙ yr⁻¹. (5) Energy outflow rate with unit of × 10⁴¹ erg s⁻¹. (6) Momentum outflow rate with unit of × 10³⁴ g cm s⁻². (7) Fractions of outflow rates of ionized gas powered by AGNs and starbursts to total outflow rate.

Download table as:  ASCIITypeset image

It is worth noting that in recent years, many works have pointed out the estimated mass and energy outflow rates may vary by one to two orders of magnitude when using different assumptions and derived quantities such as ionized gas mass, velocities, and densities (e.g., Dall’Agnol de Oliveira et al. 2021). Our work also cannot avoid these uncertainties, and the coexisting starburst and AGN outflows further complicate the measurement. However, the first-order estimated outflow rates and the relative contribution are still useful for our understanding of the impact of the starburst wind and the AGN outflow.

In NGC 7469, a biconical outflow across the east–west direction traced by [Si vi]λ 1.96 μm emission in the near-infrared was previously discovered by Müller-Sánchez et al. (2011). Robleto-Orús et al. (2021) recently reported the discovery of a patch of fast outflow in [O iii] in the circumnuclear region possibly driven by an AGN. The location is to the northwest of the nucleus, which appears to be associated with the blueshifted edge of the outflow in Müller-Sánchez et al. (2011). We have found a subgalactic-scale AGN-driven outflow extending to at least ∼2 kpc, which resembles a blueshifted tilted cone outflowing toward us. The direction of the larger scale AGN-driven outflow does not fully correspond to the circumnuclear outflow in the inner few arcseconds.

One possible explanation of the misalignment is the projection effect and the contamination of starburst-driven outflows. NGC 7469 is a nearly face-on Seyfert 1 galaxy with an inclination angle of ∼30°, which implies that the starburst wind is heavily affected by the projection along the line of sight. The inclination angle of the AGN outflow has been modeled by Müller-Sánchez et al. (2011) with ∼57° (the blueshifted cone points to the west) using [Si vi] emission on the subarcsecond scale, which also suggests that the projection effect can have influence on the AGN outflow. The detailed geometry of the outflow requires more spatially resolved data with a higher S/N, which is beyond the capability of current data. Besides the projection effect, the emission of the starburst wind could overwhelm the emission from the AGN-driven outflow around the starburst ring. In the “blue wing” BPT map (Figure 12(d)), the H ii ionization is more extended in the eastern region (A5, A6, and A7) than in the west (A1, A2, and A3) around the starburst ring, which indicates that emission from the AGN outflow in the eastern region is weaker than the western region. The asymmetric features of optical line emissions (Figure 6) are consistent with this scenario. This may well explain why Robleto-Orús et al. (2021) only found outflows from a small region in the west region inside the starburst ring, which was attributed to be driven by an AGN. Moreover, Robleto-Orús et al. (2021) distinguish the AGN outflow only based on the kinematics and the BPT diagram of narrow component emission, while our approach is complementary to identify outflows with broad wings in emission lines. In reality, it is more likely that the AGN outflow and the starburst wind both contribute to the kiloparsec scale outflow in NGC 7469. The outflowing gas driven by a starburst could also become photoionized by the AGN once entering the AGN ionization cone, and the line ratios may be altered to values corresponding to AGN ionization (see Section 4.2).

The diffuse soft X-ray emission in NGC 7469 has been found by Mehdipour et al. (2018) using the longest Chandra observation (see Section 2.3). They suggested that the diffuse soft X-ray emission is coronal emission from a nuclear starburst ring. Our results show that the ionized outflows driven by an AGN reach to ∼2 kpc, which is fully in agreement with the size of the diffuse soft X-ray emission (see Figures 5 and 12). The asymmetry of soft X-ray is also consistent with [O iii] emission generally (Figure 6). We have shown in Figure 12 that the starburst wind is mainly concentrated in the circumnuclear regions in and around the starburst ring. Therefore, it is plausible that the AGN-driven outflow may contribute to a part of this diffuse soft X-ray emission especially on a kiloparsec scale, besides the main emission from the starburst ring.

Figure 13 shows the outflow rates as a function of the AGN bolometric luminosity following Fiore et al. (2017). Our measurement of the NGC 7469 AGN outflow is consistent with the best-fit correlation. This implies the properties of the NGC 7469 outflow are rather typical of the sources in Fiore et al. (2017).

Zoom In Zoom Out Reset image size

Theoretically the AGN outflow can be energy-driven or momentum-driven according to the different cooling efficiencies (e.g., Zubovas & King 2012). Considering the bolometric luminosity of the AGN, L_bol = 10^44.53 erg s⁻¹ (Ponti et al. 2012), the momentum of AGN radiation is . As shown in Table 1, the momentum flux of the kiloparsec-scale AGN outflow is , which is consistent with the momentum-driven scenery. The kinetic coupling efficiency of AGN-driven outflows can be estimated as , which is lower than the threshold of 0.5% suggested by the “two-stage” feedback model by Hopkins & Elvis (2010). The low value of the kinetic coupling efficiency might suggest that the kiloparsec-scale AGN outflow does not significantly affect the growth of the host galaxy. Note that the kinetic coupling efficiency estimated here is only based on ionized gas outflow driven by the AGN; other phases of outflows and starburst winds are not included. Whereas cold gas outflow in NGC 7469 can be important, previous works (e.g., Izumi et al. 2015) have shown no significant evidence of molecular or neutral outflows have been found.

The energy outflow rate of the starburst-driven wind can be expected by the equation as follows (Fiore et al. 2017):

where ψ denotes the fraction of massive stars under a certain initial mass function (IMF), is the number of supernova (SN) per solar mass, is the total luminosity for each SN, and η denotes the efficiency from total luminosity transform to kinetic power of ISM. Assuming the Salpeter IMF, , , and η = 0.1, is expected at ∼10⁴² erg s⁻¹ adopting star formation rate (SFR) ∼48 M_⊙ yr⁻¹ (Pereira-Santaella et al. 2011). This value is broadly consistent with estimated by us, which indicates the SN process can power the starburst wind in NGC 7469.

Combining the [O iii] kinematics maps (Figure 10) and the “blue wing” BPT map (Figure 12), the kinematics of the starburst wind in the east region around the starburst ring show lower velocity than the AGN-driven outflows in the west region, which is consistent with the findings of Robleto-Orús et al. (2021). However, considering the outflow rates (see Table 1 and Section 3.4), the starburst wind is more powerful than the AGN-driven outflow due to the higher outflowing mass in the starburst wind. These results indicate that the starburst wind could show slower kinematics but is energetically more powerful than the AGN-driven outflow in NGC 7469.

According to the “blue wing” BPT map, impact of the starburst wind is concentrated around the starburst ring, and outflows on the larger scale (∼2 kpc) are mainly driven by the AGN. This result may suggest that the starburst mainly drives a wind on a small scale (100 pc) in NGC 7469, while on the larger scale (kiloparsec), the AGN becomes the main powering source driving the outflow. Such a dynamic scenario suggests that the ionized outflow in NGC 7469 should be a joint contribution from stellar and AGN feedback. Ionized gas clouds in the starburst ring are constantly blown out of the disk by starbursts. When these clouds enter the AGN ionization cone and are far away from the starburst ring, they will be ionized and become photoionized by the AGN.

In many nearby Seyfert galaxies, a starburst nuclear ring and a galactic outflow can be found similar to NGC 7469. For example, a star formation ring and a kiloparsec-scale biconical ionized outflow can be found in Seyfert 1.8 galaxy NGC 1365 (see Wang et al. 2009a; Venturi et al. 2018, and references therein). Because the biconical outflow is mainly classified as AGN photoionization in the BPT diagram and its mass outflow rate is similar to that of nuclear AGN wind detected by X-ray, Venturi et al. (2018) attributed the driving source of the outflow to the AGN. Using the kinematically resolved BPT diagram and map, Mingozzi et al. (2019) further confirmed that the ionization source of the kiloparsec-scale outflow in NGC 1365 is dominated by the AGN, and the line ratios of the outflow are dominated by SF ionization only in the starburst ring (see Figure D.1 in Mingozzi et al. 2019). Compared to NGC 1365 (SFR ∼ 5.6 M_⊙ yr⁻¹, Alonso-Herrero et al. 2012), the starburst wind of NGC 7469 is more energetic, which might be attributed to the higher star formation rate of NGC 7469 (SFR ∼ 48 M_⊙ yr⁻¹). Both galaxies contain circumnuclear starburst rings and AGNs in the nuclear region; their outflows can be driven by different sources, i.e., AGNs and starbursts.

In most previous studies, outflows in galaxies are often assumed to be driven by a single powering source (an AGN or starburst) for simplicity, which seems appropriate for galaxies like NGC 1365 but not the ones like NGC 7469. Our results suggest that the starburst wind and the AGN outflow can both be important in some cases in terms of energetics. In the local universe, many (U)LIRGs containing both starburst and AGN activities are rather similar to NGC 7469, which can possess both powerful starburst winds and the AGN outflow. In the case of high redshift quasars, it is generally expected that nuclear starburst and AGN activities can both be more powerful than local Seyfert galaxies (e.g., Fabian 2012; Förster Schreiber & Wuyts 2020). NGC 7469 is an excellent example for further studying the feedback from both SF and AGN processes.

As shown in Figure 9, Δv_Hα − v_Hα,peak and W80_Hα maps of Hα present a redshifted, possibly inflow-like feature in the northeast and east regions around the starburst ring. Theoretical work and many observations suggested that a bar-like structure in galaxies can dynamically drive molecular gas inflows and enhance star formation in the central region (e.g., Ellison et al. 2011; Wang et al. 2012a). A bar-like or spiral structure in molecular gas along the northeast to southwest has been detected by Davies et al. (2004), which is partially coincident with the circumnuclear inflow-like structure connecting the CND and the starburst ring . However, no stellar bar is found in the infrared (Genzel et al. 1995; Scoville et al. 2000) or radio (Condon et al. 1991; Orienti & Prieto 2010). Davies et al. (2004) also reported that no molecular gas inflow or other kinematics characteristics expected for a bar have been observed along the bar-like structure. Izumi et al. (2015) further suggest that this feature is possibly not a bar but several spiral structures blending for the lack of spatial resolution. Nevertheless, Izumi et al. (2015) noted that the existence of a faint stellar bar cannot be ruled out. In addition to the bar, the tidal interaction due to galaxies merging can also drive gas inflows and starburst activities in the central region of galaxies. In our case, NGC 7469 and IC 5283 are undergoing the merger process, and the nuclear starburst ring in NGC 7469 is believed to be produced by the tidal interaction with IC 5283 (Genzel et al. 1995). We suggest the inflow-like features in the Hα nonparametric kinematics maps might not be driven by the bar, but instead by the tidal interaction between NGC 7469 and IC 5283.

There exists another inflow-like feature in the southeast region of the FOV, approximately 4″ away from the nucleus (Figure 9). In the “narrow peak” BPT map, this region is dominated by LIER and composite emission, while star-forming, LIER, and the AGN all exist in this region in the “blue wing” BPT map. It is likely that a stream of cold gas is falling into the disk, and spatially superimposed by outflows from the AGN. However, the quality of current data is insufficient to further verify this scenario.