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Spatially Resolved Kinematics of Ionized Gas with CFHT’s SITELLE in the Merging Luminous Infrared Galaxy: Mrk 266 - Host of Dual-AGN Maya Merhi,1 Andreea Petric,2, 3 Laurie Rousseau-Nepton, Simon Prunet, Nicolas Flagey,4 and Laurent Drissen, Carmelle Robert5

1Lycoming College, 700 College Pl. Williamsport, PA 17701, USA 2Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA 3CanadaFranceHawaii Telescope, 65-1238 Mamalahoa Highway, Kamuela, HI 96743, USA 4CanadaFranceHawaii Telescope, 65-1238 Mamalahoa Hi, Kamuela, HI 96743, USA 5Universite Laval,Quebec, QC, Canada, G1V0A6A

Abstract We present the first wide-field study of the spatially resolved ionized gas kinematics in the well studied, nearby dual-AGN host Markarian 266 (Mrk 266, NGC 5256). Mrk 266 is a gas-rich luminous 11 infrared galaxy (LIRG: galaxy with LIR > 10 L ) merger at z ∼ 0.0278 that hosts Mrk 266 SW - a Seyfert, and Mrk 266 NE - a LINER. Using the Canada France Hawaii Telescope’s (CFHT’s) SITELLE instrument we study the effect of dual-AGN on Mrk 266’s ISM and the surrounding medium. We present the morphologies and kinematics of the Hα, [NII], Hβ, and [OIII] emissions. Using emission line diagnostics, we find that 5% of the Hα gas comes from new stars in HII regions, while 35% is composite (LINER + HII) emission, and 50% is from shocked gas, either associated with the AGN, or with the tidal disruption. Mrk 266’s complex [OIII] dynamics allow us to speculate that Mrk 266 is analogous to some of the high redshift, dusty systems observed to have high velocity [OIII] outflows. We also suggest that galaxies like Mrk 266 enrich the circumgalactic medium (CGM) in agreement with theoretical work on the role of mergers in transporting metals to the CGM.

1. INTRODUCTION

11 Luminous Infrared Galaxies (LIRGs: galaxies with LIR > 10 L ) are fundamental to the study of galaxy evolution. LIRGs form stars faster than nearby normal galaxies, and in the local universe (z < 0.088 ) 20% of LIRGs contain growing super massive black holes known as active galactic nuclei (AGN) that emit more energy in the infrared than the rest of the emission in the galaxy combined (e.g, Sanders et al. 1988; Armus et al. 2009; Petric et al. 2011; Petric et al. 2018). Half of nearby LIRGs are gravitationally interacting systems, and ∼ 10% exhibit large-scale outflows known as superwinds (Mazzarella et al. 2012; Petric et al. 2011; Rich et al. 2014). Thus, LIRGs exhibit interesting physical processes known to shape galaxies, dominate the total star formation density at z ∼ 1 , and are an important population at higher redshift (Le Floc’h et al. 2005; Magnelli et al. 2009).

Nearby merging LIRG systems are ideal targets in which to study the connections between gravitational galactic interactions and black hole growth. Merging gas-rich galaxies trigger AGN, as galaxy-wide shocks decrease the gas’ angular momentum and kinetic energy. In a system with two AGN, gas is funneled toward the center of the systems, feeding the central supermassive black holes (SMBHs) and powering AGN activity, while the nuclei are still apart (Colpi et al. 2009). The study of gas-rich merging systems with two AGN is integral to the understanding of galaxy merger evolution, because dual-AGN systems represent a short-lived, but rich dynamical phase of the galaxy merger evolutionary path. However, observations of dual-AGN are rare because most of their activity occurs in small and often obscured regions, and because the duration of the AGN duty-cycle and gas motions associated with the mergers appear to conspire. 2 Merhi et al.

One of the most intriguing LIRGs found in the local universe is Mrk 266 (Figure1). Mrk 266 is a gas-rich merger that harbors dual-AGN: Mrk 266 SW - a Seyfert, and Mrk 266 NE - a low-ionization nuclear emission-line region (LINER). While the true nature of LINERs has been vigorously debated in the literature, Kewley et al.(2006) show that LINERs are AGN, and that the Seyfert/LINER dichotomy is analogous to the high-low state modes in X-ray binary states. Mazzarella et al.(2012) used multi-wavelength photometric data together with several MIR low- resolution spectra to study Mrk 266. These authors proposed that Mrk 266 belongs to an evolutionary path in which dual-AGN with kiloparsec separations are predecessors to binary AGN with parsec-scale orbital radii. Mazzarella et al. (2012), however, lacked kinematic information throughout entire system. As such, both the gas depletion rates and merger time-scales are uncertain in their investigation.

We observed Mrk 266 using SITELLE (Spectrom`etreImageur `aTransform´eede Fourier pour l’Etude en Long et en Large de raies d’Emission) at the Canada-France-Hawaii Telescope (CFHT). We used SITELLE’s large field of view to probe the large merging systems including tidal tales, kiloparsec winds, and the environment surrounding the dual-AGN. Here, we take advantage of the wide field, spatial, and velocity resolution of the SITELLE instrument at CFHT to measure the amount of Hα and Hβ line emissions, from which we derive extinction corrected star-formation rates. This, together with published maps of cold molecular gas, will give us a better estimate of the depletion time- scales associated with star-formation. We use emission line diagnostics to quantify the amount of shocked gas, and assess the impact of this gas on the star-formation evolution of the systems. We also derive velocity and dispersion maps to investigate how outflowing gas may impact the circumgalactic medium. In this paper, we also briefly explore the possible analogies between Mrk 266 and high redshift dusty quasars with powerful outflows.

Figure 1: Combined image of Mrk 266, Hα at 6563A˚ and the [NII] doublet at 6548A˚ and 6583A˚ and continuum emission in SITELLE’s SN3 filter. The σ limit of this integrated emission map is 1.340 × 10−18. Mrk 266 is a complex system: two bright nuclei containing more than 13% AGN emission (Mazzarella et al. 2012), a bridge of shocked gas between the two nuclei, and a filamentary nebulae of ionized hydrogen (Armus et al. 1990; Petrosian et al. 1980). We mark those regions in Figure2. Ionized gas Kinematics in dual-AGN host Mrk 266 3

Figure 2: Image of Mrk 266 showing the features of interest. Features of interest identified in red: appearance of superwinds (left arrow), Mrk 266 NE which is classified as a LINER (left circle), Mrk 266 SW which is classified as a Seyfert 2 (right circle), Northern Loop (right arrow).

2. METHODOLOGY

Mazzarella et al.(2012) point out several striking features in Mrk 266: (1) the NE nucleus, (2) the SW nucleus, (3) extending ∼ 2500 (15kpc) to the north is a fragmented, filamentary structure known as the Northern Loop, (4) faint emission extending ∼ 6000 (24kpc) to the southeast from the center of the system appears to be tidal debris. The morphology and vast extend of emission are consistent with numerical simulations of tidal debris created during major mergers (e.g Dubinski et al. 1999; Stoehr et al. 2006). Throughout this paper, we will refer to those major structures detailed by the Mazzarella et al.(2012) study as the Northern loop, the NE nucleus, the SW nucleus, the bridge, and the Southern extended emission. Mrk 266 is at a redshift of 0.0278 corresponding to a recession velocity of 8400 km/sec. We adapt the cosmological parameters of: Hubble parameter - h = 0.7, matter denisty - Ωm = 0.3, and dark energy density - ΩΛ = 0.7, which correspond to a luminosity distance of 129 Mpc and a spatial scale of 0.59 kpc arcsec−1.

2.1. Observations

On 11 and 12 May 2019, Mrk 266 (RA, Dec [J2000]: 13h 38m 17.5s +48d 16m 37s) was observed with SITELLE on the Canada France Hawaii Telescope. The seeing on both nights varied between 0.7 ” to 0.9 ”. SITELLE’s FOV is 11 by 11 arcmuinutes, allowing us a first look at the 100 kpc extended emission kinematics in a nearby dual- AGN system. We use the SN2 filter (480-520 nm) to map the Hβ at 4861A,˚ and [OIII] at 4959A,˚ and 5007A˚ line emissions and the SN3 filter (651-685 nm) to map the Hα at 6563A˚ and [NII] at 6548A˚ and 6583A.˚ Table1 gives the observing parameters. 4 Merhi et al.

Table 1: SITELLE observations of Mrk 266

Lines Filter Res. (λ/∆λ) Steps Exp. time/step Int. time [hr] Seeing Hα, [NII] SN3 (647-685nm) 2000 347 51.0 5.23 0.7” Hβ, [OIII] SN3 (483-513nm) 1000 225 74.0 4.83 0.9”

2.2. Fitting the Spectra

Using ORCS, a software designed specially for SITELLE data cubes (Martin et al. 2015), we begin by fitting single pixels in different dynamical regions of the galaxy to estimate input parameters for the fit such as velocity and velocity dispersion (σv). Extracting these parameters determines how the ionized gas is behaving in the galaxy. We use the method fit lines in spectrum() to extract and fit the spectrum of a single pixel. The pixels are input to the method in the format: (X coordinate, Y coordinate, Radius). This method is based on the following parameters:

• the name of the line(s) to be fitted,

• ‘f model’, which indicates the fitting model to be used (sinc, sincgauss, gaussian) (Figure3),

• ‘pos def’, which defines whether emission lines are fit with the same velocity or with their own individual velocities, and ‘pos cov’, which defines the initial guess for the velocity,

• ‘sigma def’, which defines whether emission lines are fit with the same velocity dispersion (σv), or with their own individual σv, and ‘sigma cov’, which defines the initial guess for σv of the fitted line(s). These σv parameters are only relevant when fitting with sincgauss or gaussian.

We use a sincgauss model to fit the regions based on the broadness of the spectral lines we see within the galaxy. The sincgauss model is a fitting engine with a base of a sinc, convolved with a gaussian (Figure3). Various fitting tests were done to determine the quality of the final fitting parameters; such as, fitting individual pixels in various regions of the galaxy to determine the accuracy of the fit with the specified parameters.

Once our fitting parameters are determined by fitting individual pixels in the galaxy, we then begin fitting larger regions of the galaxy by extracting regions using DS9, an astronomical imaging and data visualization appli- cation. Using DS9 allows us to visualize the data and extract regions to fit in ORCS. We use the ORCS method cube.fit lines in region(), which depends on the same parameters as listed above, but instead of fitting a single pixel, it fits a region of the galaxy.

2.3. Morphology of Ionized gas

The above-mentioned ORCS fitting routine outputs FITS files containing maps of flux, velocity, σv, and all of their associated error maps. All of these maps were produced for the emission lines of interest: Hα,Hβ, [OIII] doublet, and [NII] doublet. The flux maps give the morphology of the complex structure throughout the system. The velocity and velocity width maps gives the kinematics throughout the system. Based on previous studies of Mrk 266 (Mazzarella et al. 2012; Petrosian et al. 1980), we expected to see complex kinematic structure concentrated around the nuclei, and throughout the Northern Loop and superwind regions.

2.4. Measure Luminosity and Star Formation Rate (SFR)

We used Hα and Hβ flux maps to assess the amount of extinction using the Balmer decrement (Hα/Hβ). This allowed us to correct for the amount of Hα absorbed and scattered by dust grains. We used the dust extinction Ionized gas Kinematics in dual-AGN host Mrk 266 5

1.00 gaussian1d 0.75

0.50

0.25

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0.25 2.0 1.5 1.0 0.5 0.0 0.5 1.0 1.5 2.0 (a) Gaussian model.

1.00 sinc1d 0.75

0.50

0.25

0.00

0.25 2.0 1.5 1.0 0.5 0.0 0.5 1.0 1.5 2.0 (b) Sinc model.

1.00 sincgauss1d 0.75

0.50

0.25

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0.25 2.0 1.5 1.0 0.5 0.0 0.5 1.0 1.5 2.0 (c) Sincgauss model. Figure 3: Example of three fitting model engines used in ORCS. Gaussian (a), Sinc (b), and Sincgauss (c). These fitting models are used to fit spectral lines in SITELLE datacubes (Martin et al. 2018)

methods of Calzetti et al.(2000), who assumed the dust is a uniform slab between the observed H 2 regions and the observer. First, we calculated the observed Hα luminosity using:

2 Lobs = 4πD FHα (1) where L is luminosity, D is distance, and F is flux. Then we calculated the reddening using:

(F /F ) E(B-V) = 2.2 log Hα Hβ (2) 10 2.86 The reddening equation was then applied to every pixel, and a reddening map was created. For pixels detected in Hα, but not Hβ, we used an upper limit for the Hβ emission from the standard deviation in Hβ non-detections. From the reddening map, we calculated the extinction corrected Hα luminosity from:

0.4·kHα·E(B-V) LHα(int) = LHα(obs) × 10 (3) where kHα = 3.3. Then, we calculated SFR using (Kennicutt 1998):

−42 SFRHα = 5.5 × 10 LHα[ergs/s] (4)

Applying the equation pixel by pixel allowed us to produce an extinction corrected star formation map. 6 Merhi et al.

2.5. Compute line ratio maps and BPT diagram

We used the flux maps of Hα,Hβ, [NII]6583A,˚ and [OIII]5007A˚ to compute line ratio maps of [NII]6583A/H˚ α and [OIII]5007A/H˚ β. These line ratio maps allowed us to calculate a BPT diagram, which distinguishes if the emission we are seeing in Mrk 266 is dominated by the AGN (LINER and Seyfert) or if it is coming from star forming [HII] regions (Baldwin et al. 1981).

3. RESULTS

We resolved the kinematics of the features of interest in Mrk 266: NE nucleus, SW nucleus, Northern Loop, Southern extended emission, and the bridge. Figure4 shows the features of interest and a single pixel fit of the SN3 spectral lines within the features. The single pixel fits were done using the ORCS method cube.fit lines in spectrum to fit the Hα, [NII] at 6548A,˚ and [NII] at 6548A˚ emission lines using a sincgauss model, subtracting the background sky spectrum, and using an initial velocity guess of 8453 km/s and an initial σv guess of 118 km/s. The upper left image shows Hα, and the [NII] doublet at 6548A˚ and 6583A˚ spectrum from a pixel in the NE nucleus. The image in the upper right shows the same spectrum in the Northern Loop, middle right shows spectrum in the bridge, lower left shows Southern extended emission region and lower right shows SW nucleus. Table2 shows the results from the single pixel fits in the different dynamical regions in Figure4. The pixel fits in Table2 in the regions of interest produce initial guess parameters that are required to fit the galaxy as a whole region.

Table 2: Results from Fits in Figure4

˚ ˚ Hα F lux [NII]6583A Flux [NII]6548A Flux Hα V elocity Hα σv Region (erg/cm2/s) (erg/cm2/s) (erg/cm2/s) (km/s) (km/s)

NE Nucleus 2.10(±0.033)×10−13 1.25(±0.026)×10−13 5.96(±0.023)×10−14 8372.7±2.3 184.0±2.0 SW Nucleus 2.38(±0.028)×10−13 1.34(±0.021)×10−13 4.46(±0.019)×10−14 8275.4±1.9 201.1±1.6 Northern Loop 5.24(±0.096)×10−14 1.31(±0.062)×10−14 3.79(±0.059)×10−15 8531.6±1.4 87.8±1.5 Southern Outflow 4.30(±0.096)×10−14 2.50(±0.010)×10−14 8.39(±0.034)×10−15 8152.0±2.1 121.0±2.0 The Bridge 2.50(±0.040)×10−13 1.42(±0.031)×10−13 6.50(±0.026)×10−14 8369.7±2.1 169.0±1.9

3.1. Fitting emission lines in SN3 filter

We began our fitting process by fitting the galaxy with a sinc fitting model (Figure3). We extracted output parameters from the sinc fits and used them as input parameters for the sincgauss fit. Fitting the galaxy with a sinc model first allowed us to better estimate the input parameters to get a more precise fit using the sincgauss model. Then, we fit the emission lines of interest in the galaxy using a sincgauss model. From this fit, we produced flux, velocity, and σv maps for the emission lines of interest: Hα, [NII] at 6548A,˚ and [NII] at 6583A.˚ Figure5 shows the region of Mrk 266 that was used to fit the spectral lines of interest in the SN3 filter. The region of interest (ROI) is indicated by the green circle enclosing the dual-AGN and diffuse gas surrounding the galaxy. Table3 shows the fitting parameters.

Figure 6a shows the Hα flux map, Figure 6b shows the [NII]6548A˚ flux map, Figure 6c shows the [NII]6583A˚ flux map, Figure 6d shows the Hα velocity map, Figure 6e shows the [NII]6548A˚ and [NII]6583A˚ composite flux map, and Figure 6f shows the combined σv map for all three lines. These maps were masked by filtering out all pixels with SNR < 2. Figure 6a shows a rich Hα flux gradient within the center of the galaxy. As expected, we see the highest amount of the Hα emission concentrated in the two nuclei and in the surrounding medium. Mrk 266 SW is known to have spiral arms, which are visible in Figure 6a.Hα emission is visible surrounding the two nuclei, especially the Ionized gas Kinematics in dual-AGN host Mrk 266 7

Figure 4: Combined image of Mrk 266, Hα at 6563A˚ and the [NII] doublet at 6548A˚ and 6583A˚ and continuum emission in SITELLE’s SN3 filter. The upper left image shows the Hα at 6563A˚ and the [NII] doublet at 6548A˚ and 6583A˚ spectrum from a pixel in the NE nucleus. The image in the upper right shows the same spectrum in the Northern Loop, middle right shows spectrum in the bridge, lower left shows Southern extended emission region and lower right shows SW nucleus. See in-text for details on the pixel fits.

SW nucleus, and throughout the surrounding medium and up through the Northern Loop. We see a lack of optical emission between the two nuclei, which Mazzarella et al.(2012) also saw in their optical observations of Mrk 266, and they found bright radio continuum in the region between the nuclei. Bright Hα flux emission is present throughout the Northern Loop, which was expected since it is predicted to be a powerful superwind. This Hα flux map allows us to see the structure and morphology of the galaxy. We see outflow regions stemming from the two nuclei which tell us that the nuclei are spewing material into the ISM.

For the [NII] flux maps, only parameter difference from the Hα flux map was an initial velocity guess of 8368.9 km/s. There is very similar structure in Figure 6b as there is in Figure 6a. The brightest flux emission for this map is concentrated at the two nuclei and in the surrounding medium. There is less prominent emission surrounding the SW nuclei in Figure 6b than is visible in Figure 6a. The spiral arms in the SW nuclei are less visible, and there is also less prominent [NII]6548A˚ throughout the Northern Loop than is visible in Figure 6a. The [NII]6548A˚ flux map shows less structure throughout the galaxy than the Hα, but there is still prominent [NII]6548A˚ flux emitted from the

Table 3: Sincgauss Model Fitting Parameters for SN3 Filter

Lines f model pos def pos cov sigma def sigma cov binning snr guess no filter Subtract sky Hα sincgauss 2 8368.9 1 70 1 auto True Yes NII6548A˚ sincgauss 1 8357.2 1 70 1 auto True Yes NII583A˚ sinc 1 8357.2 1 70 1 auto True Yes 8 Merhi et al.

Figure 5: Combined image of Mrk 266, Hα at 6563A˚ and the [NII] doublet at 6548A˚ and 6583A˚ and continuum emission in SITELLE’s SN3 filter. The σ limit of this integrated emission map is 1.340 × 10−18. The green circle marks the region of interest (ROI) that was extracted from DS9 and used to fit the following maps. two nuclei and in the surrounding medium. In Figure 6c, we see brighter flux emission than in Figure 6b, but still less emission than in Figure 6a. There is prominent emission surrounding Mrk 266 SW, and the spiral arms are visible, but still less prominent than in the Hα flux map. Figure 6c shows high amounts of [NII] emission and what appears to be shocked gas at the bottom of the central emission region. In Figure 6c, we see the same morphological structure as the previous two flux maps, but we see slight variations in the flux emissions between the different spectral lines.

Figure 6d shows the highest velocities in km/s throughout the Northern Loop, and the lowest velocities surrounding the SW nucleus. The high velocities found in the Northern Loop support the claim that the Northern Loop is due to powerful superwinds and gas outflows. The lowest velocities, in the lower end of the galaxy, are hypothesized to be gas inflowing to the SW nucleus. The radial velocity of the galaxy is 8353 km/s (Mazzarella et al. 2012), so the low velocities surrounding the SW nucleus and the lower region of the galaxy are negative relative to the radial velocity of the galaxy, indicating inflowing gas. Mid velocities in the galaxy are seen in the two arms stemming from the region containing the NE nucleus on the left side of the galaxy. This shows that gas is flowing outward in the regions, but the winds are not nearly as powerful as they are in the Northern Loop. Figure 6e shows similar structures as the Hα velocity map, with the highest velocities concentrated in the Northern Loop and upper regions of the galaxy, and the lowest velocities in the lower region of the galaxy. We also see mid-to-high velocities in the arms flowing to the left of the center of the galaxy, as well as in the southern outflow region.

Figure6 shows that Mrk 266 has a rich kinematic structure that can have many implications for the complex processes taking place in the galaxy. From the maps, we see many dynamical regions in Mrk 266 that provide more evidence for claims of strong superwinds and outflows taking place in the galaxy. The kinematic structure from these maps can help us have a better understanding of how a dual-AGN effects its host galaxy. Ionized gas Kinematics in dual-AGN host Mrk 266 9

(a) Hα at 6563A˚ flux map. (b) NII at 6548A˚ flux map.

(c) NII at 6583A˚ flux map. (d) Hα at 6563A˚ velocity map.

(e) NII doublet (6548A˚ and 6583A˚ ) velocity (f) Sigma map for all three emission lines of map. interest, Hα and the NII doublet (6548A˚ and 6583A˚ ). Figure 6: SN3 maps produced from fit in ROI using ORCS method cube.fit lines in region() with an initial velocity of 8357.2 km/s, 1 × 1 binning applied, and initial sigma value of 70km/s. These maps show the morphology of the galaxy and the kinematics od the emission lines in the SN3 filter.

3.2. Fitting emission lines in SN2 filter

Similar to SN3 fitting, we began by fitting the galaxy with a sinc model. However, the emission lines of interest in the SN2 filter (Hβ, [OIII]4959A,˚ [OIII]5007A)˚ all required separate fitting with a sincgauss model, and therefore independent flux, velocity, and velocity dispersion maps were produced. The lines in the SN3 filter were able to be fit all at once, however, the lines in the SN2 filter required independent fitting, possibly due to the lower resolution of the SN2 filter. The resolution in the SN2 filter is 1000, whereas the resolution in the SN3 filter is 2000. 10 Merhi et al.

Due to computation time, a smaller region of the galaxy was fitted for the lines in the SN2 filter. Figure7 shows the region that was used to fit the lines in the SN2 filter.

Figure 7: Composite image of Hβ at 4681A˚ and [OIII] doublet at 4959A˚ and 5007A.˚ This image shows the region of interest that was used to fit the emission lines in the SN2 filter. A smaller region of Mrk 266 was used to fit the emission lines in the SN2 filter than in the SN3 filter due to computation time.

Figures 8a, 8b, and 8c show the flux maps for the Hβ and the [OIII] emissions in the galaxy. The fits were done using the ORCS method cube.fit lines in region() with a sincgauss fitting engine, initial velocity of 8353 km/s, initial σv value of 100 km/s, 1 × 1 binning applied. The [OIII]5007A˚ flux map shows the most prominent emission concentrated in the two nuclei, in the surrounding medium, and in the Northern Loop, as expected. The spiral arms in Mrk 266 SW are not as prominent as they are in Figure 6a, however, we still see bright [OIII] flux surrounding the galaxy. These maps are slightly more pixelated than the maps in the SN3 filter, because the resolution in the SN2 filter is half that of the resolution in the SN3 filter. To verify the fit, the observed wavenumber was calculated given the wavelength in nm of Hβ (486.1 nm) and the redshift of Mrk 266 (0.0278), using λobs = λemit(z + 1), and then converting to wavenumber using k = 1 × 107/λ(nm), because SITELLE spectral data is given in wavenumber. With the observed wavenumber, we compared single pixel fits, using cube.fit lines in spectrum, to individual pixels from the flux map. The fluxes from the single pixel fits matched up with the fluxes from those same pixels in the map, within the error bars. This shows that the flux map is properly fitting Hβ.

The fitted Hβ flux map shows bright emission in the regions of interest that we expected. The color bar on Figure 8a shows that the brightest regions of emission have values around 1 × 10−16 erg/cm2/s. This scaling is the same for Figure 8b, which shows the flux maps of the emission lines of [OIII]4959A.˚ The flux map for [OIII]4959A˚ shows much greater emission concentrated in the Northern Loop and in the SW nucleus compared to the Hβ flux map. There is a strong outflow coming from the SW nucleus, and flowing SE from the AGN. [OIII] is an indicator of shocked gas. This flux map shows that the gas in the Northern Loop is shocked, which is likely a result of the host galaxies merging, and causing the gas throughout the system to become shocked. The scaling on the color bar in Figure 8c is larger, with the brightest emission around 3.5 × 10−16. There is brighter [OIII] emission from the line at 5007A˚ than the line at 4959A.˚ We see bright emission regions in the Northern Loop, concentrated at the two nuclei, in the area surrounding the SW nucleus, and flowing SE from the SW nucleus. We also see fairly strong [OIII]5007A˚ flux Ionized gas Kinematics in dual-AGN host Mrk 266 11

(a) Hβ at 4681A˚ flux map. (b) OIII at 4959A˚ flux map.

(c) OIII at 5007A˚ flux map Figure 8: Flux maps produced from SN2 data. These maps were all produced from a fit in the ROI using ORCS method cube.fit lines in region() with a sincgauss fitting engine, initial velocity of 8353 km/s, initial σv value of 100 km/s, 1 × 1 binning applied. These maps show the morphology of the galaxy through the SN2 emission lines.

(2.0 × 10−16) in the arms in the left region of the galaxy. These high amounts of [OIII]5007A˚ flux are another strong indicator for shocked gas throughout the system.

Figures 9a, 9b and 9c show the velocity maps for Hβ, [OIII] at 4959A,˚ and 5007A,˚ respectively. The velocity map for Hβ at 4861A˚ shows a large velocity gradient throughout the system. The greatest velocities are found in the upper and left regions of the galaxy, as well as in the center, to the left of the NE AGN. There are negative velocities relative to the radial velocity (8353 km/s) in region surrounding the SW nucleus and in the region to the left of the region between the two nuclei. There is a similar velocity gradient in the velocity map for [OIII]4959A˚ (Figure 9b). However, the color bar scale is greater, showing the brightest pixels to have velocities around 8600 km/s. These high velocities are present throughout the Northern Loop, showing outflows and super winds. We also see a bright region indicating high velocities in the southern outflow region in the lower left region of the galaxy. There are negative velocities relative to the radial velocity near the SW nucleus. Figure 9c has the same color bar scaling as Figure 8b. However, in Figure 9c, we see greater [OIII]5007A˚ velocity than in Figure 9b, specifically in the Northern Loop. This is further evidence for the outflows and superwinds taking place in the Northern Loop. Figure9 shows great kinematic detail of Mrk 266. These maps give greater evidence to support the claims of complex processes that cause complex dynamics in the system.

Figures 10a, 10b, and 10c show the velocity dispersion map for the Hβ and the [OIII] doublet in the galaxy. Velocity dispersion maps can tell us about the thermal and kinetic energy of the interacting system. More structure 12 Merhi et al.

(a) Hβ at 4681A˚ velocity map.

(b) OIII at 4959A˚ velocity map. (c) OIII at 5007A˚ velocity map Figure 9: Velocity maps produced from SN2 data. These maps were all produced from a fit in the ROI using ORCS method cube.fit lines in region() with a sincgauss fitting engine, initial velocity of 8353 km/s, initial σv value of 100 km/s, 1 × 1 binning applied. These maps show the kinematics of the galaxy through the SN2 emission lines. is visible in Figure 10b than in Figure 10a. Greater velocity dispersion is seen in the Northern Loop in Figure 10b than in Figure 10a. Figure 10c shows the velocity dispersion map for the [OIII]5007A˚ emission, which was fit using the same parameters as Figure 10b. The scaling on the color bar for Figure 10c is lower than on Figure 10b, but we do see similar structure in the two maps, and Figure 10c allows us to see more differences in the velocity dispersion in regions of the galaxy. The [OIII]5007A˚ map shows a richer velocity dispersion throughout the system than the Hβ velocity dispersion map. This shows that the [OIII] gas has more complex kinematic components.

3.3. Emission Line Analysis and Sources of Ionization in Mrk 266

Figure 11a shows the flux ratio map of Hα/Hβ. This ratio map was produced using the flux maps from Figures 6a and 8a. The typical ratio for Hα/Hβ is roughly 3:1, in favor of Hα. However, interstellar dust absorbs more blue light than red, so that ratios greater than this are typical in observations. Observed ratios of Hα/Hβ provide an interesting probe of dust in front of and within the ionized gas. Since we see ratios higher than 3:1 throughout certain areas of the galaxy, it indicates that these areas have more dust.

Figures 11b and 11c show the ratio maps for [NII]6583/Hα and [OIII]5007/Hβ, respectively. These figures were created using the flux maps for Hα,Hβ, [NII]6583A˚ and [OIII]5007A˚ shown in Figures 6a& 8a and 6c& 8c. They are used to create a BPT diagram (Baldwin, Phillips, Terlevich 1981), which classifies the sources of emission in the galaxy. A BPT diagram uses the nebular emission lines to distinguish the ionization mechanism of nebular gas. The [NII]/Hα ratio map (Figure 11b) shows quite weak emission, especially throughout the Northern Loop. We see the strongest [NII]/Hα ratio emission concentrated throughout the outside of the galaxy. The [OIII]5007/Hβ ratio Ionized gas Kinematics in dual-AGN host Mrk 266 13

(a) Hβ at 4681A˚ σv map

(b) OIII at 4959A˚ σv map. (c) OIII at 5007A˚ σv map.

Figure 10: σv maps produced from SN2 data. These maps were all produced from a fit in the ROI using ORCS method cube.fit lines in region() with a sincgauss fitting engine, initial velocity of 8353 km/s, initial σv value of 100 km/s, 1 × 1 binning applied. (a) shows Hβ at 4681A˚ σv map. (b) shows OIII at 4959A˚ σv map. (c) shows OIII at 5007A˚ σv map. map (Figure 11c) shows stronger ratio emission than [NII]/Hα. We expected to see a stronger [OIII]5007/Hβ ratio since the galaxy contains two powerful AGN, and therefore contains highly ionized gas.

Figure 12 shows the BPT diagrams created using the emission line ratios of [NII]6583/Hα and [OIII]5007/Hβ. We separated the emission into regions of AGN only, Seyfert AGN only, LINER AGN only, composite (LINER + HII Regions) and HII regions only. These separated regions are used to calculate star formation rates in section 3.4. The separations were made using the line equations in Kewley et al.(2006). The blue, red, and green lines overlayed on Figure 12 distinguish what type of emission is coming from the galaxy. The blue line labeled ‘Kewley+01’ shows the theoretical ‘maximum starburst line’ determined by the upper limit of the theoretical pure stellar photoionization models (Kewley et al. 2006). The Kewley line is used to distinguish between galaxies dominated by AGN and those dominated by star forming regions. The green line labeled ‘Kauffmann+03’ shows the modified Kewley line used to rule out possible composite galaxies. Galaxies whose emission falls under the Kauffmann line are most likely purely star forming, whereas those whose emission lies above the Kauffmann line are likely Seyfert-HII composite objects (Kewley et al. 2006). The red line labeled ‘Schawinski+07’ shows the division between galaxies with Seyfert AGN and those with LINER AGN. Galaxies with emission lying above the Schawinski line most likely contain a Seyfert AGN, and those with emission lying below the Schawinski line most likely contain a LINER AGN (Schawinski et al. 2007).

From Figure 12, it is clear that Mrk 266 has multiple sources of emission. There are high amounts of AGN emission, both Seyfert and LINER. The Seyfert emission lies above the blue and red lines, and the LINER emission lies above the Kewley+01 line and below the Schawinski+07 line. There is also significant emission in the region above 14 Merhi et al.

(a) Flux ratio map of Hα to Hβ.

(b) Flux ratio map of NII at 6583A˚ to Hα. (c) Flux ratio map of OIII at 5007A˚ to Hα. Figure 11: Ratio maps produced from Hα,Hβ, [NII] at 6583A˚ , and [OIII] at 5007A˚ . For all three maps, pixels with SNR < 2 were filtered out of the map. (a) shows the ratio map showing the flux ratio of Hα to Hβ: the minimum pixel ratio for this map is 2.00 and the maximum is 9.57. (b) shows the ratio map showing the flux ratio of [NII]6583 to Hα: the minimum pixel ratio for this map is 0.124 and the maximum is 34.600. (c) shows the ratio map showing the flux ratio of [OIII]5007 to Hβ: the minimum pixel ratio for this map is 0.079 and the maximum is 2.635. Panel (a) is used to estimate extinction corrected star formation rates, and panels (b) and (c) are used to create a BPT diagran the Kauffmann+03 line and below the Kewley+01. Emission in this region is most likely composite star formation and AGN emission (Kewley et al. 2006). Mrk 266 is most heavily dominated by AGN emission, both Seyfert and LINER, with some composite star forming and AGN emission. We see very little pure star forming region emission, which is as expected since the galaxy contains a dual-AGN, and AGN are thought to quench star formation.

3.4. Star Formation Rates

Using the methods outlined in 2.4 we calculated the reddening of the galaxy, uncorrected Hα luminosity, extinction corrected Hα luminosity, and the star formation rate (SFR). We calculated SFR from the whole galaxy, AGN emission, Seyfert emission only, LINER emission only, composite (LINER + HII) regions, and HII regions only.

Figure 13 shows the reddening map and the SFR map. Figure 13a shows the reddening map created by applying Equation (2) to Hα/Hβ ratio map. The reddening map allowed us to calculate the extinction corrected Hα luminosity using Equation (3), and from there, we calculated the extinction corrected SFR using Equation (4) (Kennicutt 1998). Figure 13b shows the SFR map created following the steps outlined above. We found total SFR −1 −1 of 41.28 M yr . We found SFR from total AGN only emission to be 7.30 M yr , from Seyfert only to be 6.77 −1 −1 −1 M yr , from LINER only to be 0.52 M yr , from composite (LINER + HII regions) to be 15.6 M yr , and Ionized gas Kinematics in dual-AGN host Mrk 266 15

(a) BPT diagram showing the whole galaxy’s (b) BPT diagram showing only AGN emission emission

(c) BPT diagram showing only Seyfert emission (d) BPT diagram showing only LINER emis- sion

(e) BPT diagram showing composite AGN + (f) BPT diagram showing only HII regions. HII regions. Figure 12: BPT diagrams showing different regions of emission in Mrk 266. The blue, red, and green lines overlayed on the figures distinguish what type of emission is coming from the galaxy. The blue line is the ‘Kewley+01’ line, the green line is the ‘Kauffmann+03’ line, and the red line is the Schawinski+07. See in text for details on how the lines separate emission. 16 Merhi et al.

−1 from HII regions only to be 2.48 M yr . We found that ∼ 5 ± 2% of the Hα emission comes from HII regions only, ∼ 35 ± 3% comes from composite (LINER + HII) regions, and ∼ 50 ± 5% comes from the AGN. Most of the ionizing radiation likely comes from shocked gas either associated with the AGN or with the tidal disruption.

(a) Reddening map created using Hα/Hβ ratio map, and applying Equation (2) to ratio map.

(b) SFR map created following the steps outlined in Section 2.4 using Equation (4) and applying it to every pixel. Figure 13: Reddening E(B-V) and SFR maps. The map in panel (a) is used in order to calculate the map in panel (b), detailed in 2.4. Panel (b) shows the total star formation map in the galaxy. These maps are used to calculate the total star formation rates in the galaxy, and in the features of interest. Using these maps and Figure 12, we calculate the sources Hα emission. Ionized gas Kinematics in dual-AGN host Mrk 266 17

4. DISCUSSION AND CONCLUDING REMARKS

We used optical imaging spectroscopy with SITELLE, a wide-field Fourier Transfrom Spectrograph, on the Canada France Hawaii Telescope to study Mrk 266’s ionized gas kinematics and excitation conditions. Analyzing these properties helps us to understand its star-formation properties, the impact of the dual-AGN on total ISM reservoir, and the connections between merging gas-rich galaxies and the enrichment of the circum-galactic medium. Mrk 266 provides an excellent low-z laboratory to study the triggering and evolution of dual-AGN systems.

We used the [OIII]/Hβ versus [NII]/Hα emission line ratios, and the widths of the lines to separate the Hα emission that originates in HII regions from that produced by AGN and/or tidal shocks. We found that ∼ 5 ± 2% of Hα comes from new stars in HII regions, while ∼ 35 ± 3% is of composite (LINER + HII) origin, and ∼ 50 ± 5% comes from the AGN. We found that most of the ionizing radiation comes from shocked gas either associated with the AGN or with the tidal disruption.

Our extinction corrected star-formation rates (SFR) estimated from the pure star-formation, Hα is on the −1 9 order of 2 M yr . This suggests that the current available gas reservoir (∼ 3.4 × 10 M Mazzarella et al.(2012)) will be consumed in ∼ 3Gyr, which gives a timescale for the system to become an elliptical. This timescale is longer than the time between an object at z ∼ 3 and z ∼ 0.278, suggesting that if Mrk 266 was at z ∼ 2.5, we would see today an elliptical galaxy, without much star-formation, unless there is significant in-fall and cooling of gas from the outer tidal tails.

Perrotta et al.(2019) investigates Extremely Red Quasars (ERQs) which are heavily-reddened quasars at redshift z ∼ 2-3 that might be seen during a short lived phase of quasar/galaxy evolution known as the “blow-out” phase. ERQs exhibit the broadest and most blue-shifted [OIII] at 4959A˚ and 5007A˚ emission ever reported (Perrotta et al. 2019). ERQs have incredible large velocity widths ranging between 2053 and 7227 km/s, and maximum outflow speeds up to 6702 km/s (Perrotta et al. 2019). ERQs also have, on average, [OIII] outflow velocities about 3 times greater than those of luminosity matched blue quasar samples. In their study, Perrotta et al.(2019), showed that the faster [OIII] outflows in ERQs are strongly correlated with their extreme red colors, and NOT the quasar luminosity, and their results reveal that ERQs have the potential to strongly affect the evolution of host galaxies (Perrotta et al. 2019). The [OIII] kinematics and morphology of Mrk 266 make this target analogous to high redshift, dusty Quasars, with massive outflows of ionized gas and metals. If Mrk 266 were to be observed at a high redshift, it may look similar to these ERQs.

We also investigated the impact a system like Mrk 266 has on the circum-galactic medium (CGM). The CGM is the gas that surrounds a galaxy and hosts a significant amount of metals (Hani et al. 2018). The CGM acts as a mediator between the galaxy and the extra-galactic medium, however, our understanding of how galaxy mergers impact the CGM remains deficient (Hani et al. 2018). Galaxy mergers are often invoked to explain the presence of metals and low ionization species in the CGM (Hani et al. 2018). Despite the possibly significant influence of galaxy mergers on the CGM, the details of the effect of galaxy mergers on the CGM remains relatively unexplored and we are currently lacking clear predictions of how the CGM will be affected during the merger process (Hani et al. 2018).

Using a simple kinematic investigation of the highest velocity gas we assessed that if (1) the line-of-site velocity is similar to the velocity the gas has moving away from the center of mass, (2) the amount of dark matter in 11 11 the inner 100 kpc is less than 4×10 M and the total barryonic mass is 1×10 M , then 3% of the observed shocked gas is unbound and will reach 500kpc as predicted by Hani et al.(2018). This result indicates that the outflowing [OII] gas in Mrk 266 is enriching the CGM with metals.

From our work, we further confirm the complex ionized gas kinematics that have been briefly explored in previous studies of Mrk 266 (Mazzarella et al. 2012; Petrosian et al. 1980) using spatially resolved IFU data from CFHT’s SITELLE instrument. Future work with Mrk 266 SITELLE data will focus on a dynamical model for Mrk 266 combining the ionized gas data presented here with VLA observations of the neutral hydrogen emission to assess the likely merger geometry and timescales. 18 Merhi et al.

5. ACKNOWLEDGEMENTS

Maya Merhi would like to thank Nader Haghighipour and Aaron Do for their teaching and guidance through- out the duration of this work. She would like to thank the graduate students at University of Hawaii at Hilo for their guidance and help, especially Jessica Schonhut Stasik for her dedication to teaching, aiding, and providing support during the course of this work. Maya Merhi acknowledges support from Research Experience for Undergraduate pro- gram at the Institute for Astronomy, University of Hawaii-Manoa funded through NSF grant 6104374. Maya Merhi would like to thank the Institute for Astronomy for their kind hospitality during the course of this project. This work is based on observations made by Canada-France-Hawaii Telescope. We wish to extend our special thanks to those of Hawaiian ancestry on whose sacred mountain of Maunakea, we are privileged to be guests. Without their generous hospitality, the observations presented herein would not have been possible.

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