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Thaisa Storchi-Bergmann

Publications and source records attributed to Thaisa Storchi-Bergmann.

At least 55 records · Page 3Linked to original sources

Gas inflows in the polar ring of NGC 4111: the birth of an AGN

We have used Hubble Space Telescope (HST) images, SAURON Integral Field Spectroscopy (IFS) and adaptative optics assisted Gemini NIFS near-infrared K-band IFS to map the stellar and gas distribution, excitation and kinematics of the inner few kpc of the nearby edge-on S0 galaxy NGC 4111. The HST images map its $\approx$ 450 pc diameter dusty polar ring, with an estimated gas mass $\ge10^7$ M$_\odot$. The NIFS datacube maps the inner 110 pc radius at $\approx$ 7 pc spatial resolution revealing a $\approx$ 220 pc diameter polar ring in hot ($2267\pm166$ K) molecular H$_2$ 1-0 S(1) gas embedded in the polar ring. The stellar velocity field shows disk-dominated kinematics along the galaxy plane both in the SAURON large-scale and in the NIFS nuclear-scale data. The large-scale [O III] $\lambda5007$ Åvelocity field shows a superposition of two disk kinematics: one similar to that of the stars and another along the polar ring, showing non-circular motions that seem to connect with the velocity field of the nuclear H$_2$ ring, whose kinematics indicate accelerated inflow to the nucleus. The estimated mass inflow rate is enough not only to feed an Active Galactic Nucleus (AGN) but also to trigger circumnuclear star formation in the near future. We propose a scenario in which gas from the polar ring, which probably originated from the capture of a dwarf galaxy, is moving inwards and triggering an AGN, as supported by the local X-ray emission, which seems to be the source of the H$_2$ 1-0 S(1) excitation. The fact that we see neither near-UV nor Br$γ$ emission suggests that the nascent AGN is still deeply buried under the optically thick dust of the polar ring.

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Gemini NIFS survey of feeding and feedback processes in nearby Active Galaxies: VI -- Stellar Populations

We use Gemini Near-Infrared Integral Field Spectrograph (NIFS) adaptive optics assisted data-cubes to map the stellar population of the inner few hundred parsecs of a sample of 18 nearby Seyfert galaxies. The near-infrared light is dominated by the contribution of young to intermediate old stellar populations, with light-weighted mean ages $ _L\ \lesssim $ 1.5\,Gyr. Hot dust ($HD$) emission is centrally peaked (in the unresolved nucleus), but it is also needed to reproduce the continuum beyond the nucleus in nearly half of the sample. We have analysed the stellar population properties of the nuclear region and their relation with more global properties of the galaxies. We find a correlation between the X-ray luminosity and the contributions from the $HD$, featureless continuum $FC$ and reddening $A_V$. We attribute these correlations to the fact that all these properties are linked to the mass accretion rate to the active galactic nuclei (AGN). We also find a correlation of the bolometric luminosity $log(LBol_{obs})$ with the mass-weighted mean age of the stellar population, interpreted as due a delay between the formation of new stars and the triggering/feeding of the AGN. The gas reaching the supermassive black hole is probably originated from mass loss from the already somewhat evolved intermediate-age stellar population ($ _L \lesssim $ 1.5\,Gyr). In summary, our results show that there is a significant fraction of young to intermediate age stellar populations in the inner few 100\,pc of active galaxies, suggesting that this region is facing a rejuvenation process in which the AGN, once triggered, precludes further star formation, in the sense that it can be associated with the lack of new star formation in the nuclear region.

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Gas phase metallicity determinations in nearby AGNs with SDSS-IV MaNGA: evidence of metal poor accretion

We derive the metallicity (traced by the O/H abundance) of the Narrow Line Region ( NLR) of 108 Seyfert galaxies as well as radial metallicity gradients along their galaxy disks and of these of a matched control sample of no active galaxies. In view of that, observational data from the SDSS-IV MaNGA survey and strong emission-line calibrations taken from the literature were considered. The metallicity obtained for the NLRs %each Active Galactic Nucleus (AGN) was compared to the value derived from the extrapolation of the radial oxygen abundance gradient, obtained from \ion{H}{ii} region estimates along the galaxy disk, to the central part of the host galaxies. We find that, for most of the objects ($\sim 80\,\%$), the NLR metallicity is lower than the extrapolated value, with the average difference ($ $) between these estimates ranging from 0.16 to 0.30 dex. We suggest that $ $ is due to the accretion of metal-poor gas to the AGN that feeds the nuclear supermassive black hole (SMBH), which is drawn from a reservoir molecular and/or neutral hydrogen around the SMBH. Additionally, we look for correlations between $D$ and the electron density ($N_{\rm e}$), [\ion{O}{iii}]$λ$5007 and H$α$ luminosities, extinction coefficient ($A_{V})$ of the NLRs, as well as the stellar mass ($M_{*}$) of the host galaxies. Evidences of an inverse correlation between the $D$ and the parameters $N_{\rm e}$, $M_{*}$ and $A_{\rm v}$ were found.

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The Eddington ratio-dependent changing look events in NGC 2992

We present an analysis of historical multi-wavelength emission of the Changing Look (CL) Active Galactic Nucleus (AGN) in NGC 2992, covering epochs ranging from 1978 to 2021, as well as new X-ray and optical spectra. The galaxy presents multiple Seyfert type transitions from type 2 to intermediate-type, losing and regaining its H$α$ BEL recurrently. In X-rays, the source shows intrinsic variability with the absorption corrected luminosity varying by a factor of $\sim$ 40. We rule out tidal disruption events or variable obscuration as causes of the type transitions and show that the presence and the flux of the broad H$α$ emission line are directly correlated with the 2-10 keV X-ray luminosity (L$_{2-10}$): the component disappears at L$_{2-10} \leq 2.6\times10^{42}$\ergcms, this value translates into an Eddington ratio ($λ_{\rm Edd}$) of $\sim$ 1\%. The $λ_{\rm Edd}$ in which the BEL transitions occur is the same as the critical value at which there should be a state transition between a radiatively inefficient accretion flow (RIAF) and a thin accretion disk, such similarity suggests that the AGN is operating at the threshold mass accretion rate between the two accretion modes. We find a correlation between the narrow Fe K$α$ flux and $λ_{\rm Edd}$, and an anti-correlation between full-width at half maximum of H$α$ BEL and $λ_{\rm Edd}$, in agreement with theoretical predictions. Two possible scenarios for type transitions are compatible with our results: either the dimming of the AGN continuum, which reduces the supply of ionising photons available to excite the gas in the Broad Line Region (BLR), or the fading of the BLR structure itself occurs as the low accretion rate is not able to sustain the required cloud flow rate in a disk-wind BLR model.

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AGN STORM 2: I. First results: A Change in the Weather of Mrk 817

We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura-Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission line variability. The correlation recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured state. The short CIV and Ly alpha lags suggest that the accretion disk extends beyond the UV broad line region.

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The Cepheid Distance to the Narrow-Line Seyfert 1 Galaxy NGC 4051

We derive a distance of $D = 16.6 \pm 0.3$~Mpc ($μ=31.10\pm0.04$~mag) to the archetypal narrow-line Seyfert 1 galaxy NGC 4051 based on Cepheid Period--Luminosity relations and new Hubble Space Telescope multiband imaging. We identify 419 Cepheid candidates and estimate the distance at both optical and near-infrared wavelengths using subsamples of precisely-photometered variables (123 and 47 in the optical and near-infrared subsamples, respectively). We compare our independent photometric procedures and distance-estimation methods to those used by the SH0ES team and find agreement to 0.01~mag. The distance we obtain suggests an Eddington ratio $\dot{m} \approx 0.2$ for NGC 4051, typical of narrow-line Seyfert 1 galaxies, unlike the seemingly-odd value implied by previous distance estimates. We derive a peculiar velocity of $-490\pm34$~km~s$^{-1}$ for NGC 4051, consistent with the overall motion of the Ursa Major Cluster in which it resides. We also revisit the energetics of the NGC 4051 nucleus, including its outflow and mass accretion rates.

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Gemini NIFS survey of feeding and feedback in nearby Active Galaxies -- IV. Excitation

The near-infrared spectra of Active Galactic Nuclei (AGN) present emission lines of different atomic and molecular species. The mechanisms involved in the origin of these emission lines in AGN are still not fully understood. We use J and K band integral field spectra of six luminous ($43.1<\log L_{\rm bol}/({\rm erg s^{-1}})<44.4$) Seyfert galaxies (NGC 788, Mrk 607, NGC 3227, NGC 3516, NGC 5506 and NGC 5899) in the Local Universe ($0.0039<z<0.0136$) to investigate the gas excitation within the inner 100-300 pc radius of the galaxies at spatial resolutions of a few tens of parsecs. In all galaxies, the H$_2$ emission originates from thermal processes with excitation temperatures in the range 2400-5200 K. In the high line ratio (HLR) region of the H$_2$/Br$γ$ vs. [Fe II]/Pa$β$ diagnostic diagram, which includes 29 % of the spaxels, shocks are the main excitation mechanism, as indicated by the correlation between the line widths and line ratios. In the AGN region of the diagram (64 % of the spaxels) the H$_2$ emission is due to the AGN radiation. The [Fe II] emission is produced by a combination of photoionisation by the AGN radiation and shocks in five galaxies and is dominated by photoionisation in NGC 788. The [S IX]1.2523$μ$m coronal emission line is present in all galaxies, and its flux distributions are extended from 80 to 185 pc from the galaxy nuclei, except for NGC 5899, in which this line is detected only in the integrated spectrum.

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Interactions between the large-scale radio structures and the gas in a sample of optically selected type 2 quasars

The role of radio mode feedback in non radio-loud quasars needs to be explored in depth to determine its true importance. Its effects can be identified based on the evidence of interactions between the radio structures and the ambient ionised gas. We investigate this in a sample of 13 optically selected type-2 quasars (QSO2) at z<0.2 with FIRST radio detections. None are radio loud. All show complex optical morphologies, with signs of distortion across tens of kpc due to mergers/interactions. The radio luminosity has an AGN component in 11/13 QSO2. It is spatially extended in 9 of them (jets/lobes/bubbles/other). The maximum sizes are in the range few kpc to ~500 kpc. Evidence for radio-gas interactions exist in 10/13 QSO2; that is, all but one with confirmed AGN radio components. The interactions are identified across different spatial scales, from the nuclear narrow line region up to tens of kpc from the AGN. Large scale low/modest power radio sources can exist in radio-quiet QSO2, which can provide a source of feedback on scales of the spheroidal component of galaxies and well into the circumgalactic medium in systems where radiative mode feedback is expected to dominate.

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Exploring the AGN-Merger Connection in Arp 245 I: Nuclear Star Formation and Gas Outflow in NGC 2992

Galaxy mergers are central to our understanding of galaxy formation, especially within the context of hierarchical models. Besides having a large impact on the star formation history, mergers are also able to influence gas motions at the centre of galaxies and trigger an Active Galactic Nucleus (AGN). In this paper, we present a case study of the Seyfert galaxy NGC 2992, which together with NGC 2993 forms the early-stage merger system Arp 245. Using Gemini Multi-Object Spectrograph (GMOS) integral field unit (IFU) data from the inner 1.1 kpc of the galaxy we were able to spatially resolve the stellar populations, the ionisation mechanism and kinematics of ionised gas. From full spectral synthesis, we found that the stellar population is primarily composed by old metal-rich stars (t $\geq$ 1.4 Gyr, $Z \geq 2.0$\zsun), with a contribution of at most 30 per cent of the light from a young and metal-poor population (t $\leq$ 100 Myr, $Z \leq 1.0$\zsun). We detect \halpha and \hbeta emission from the Broad Line Region (BLR) with a Full Width at Half Maximum (FWHM) of $\sim$ 2000\kms. The Narrow Line Region (NLR) kinematics presents two main components: one from gas orbiting the galaxy disk and a blueshifted (velocity $\approx$ -200\kms) outflow, possibly correlated with the radio emission, with mass outflow rate of $\sim$ 2 M$_{\odot}$ yr$^{-1}$ and a kinematic power of $\sim$ 2 $\times 10^{40}$ erg s$^{-1}$ (\Eout/\Lbol $\approx$ 0.2 per cent). We also show even though the main ionisation mechanism is the AGN radiation, ionisation by young stars and shocks may also contribute to the emission line ratios presented in the innermost region of the galaxy.

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Spatially resolved BPT mapping of nearby Seyfert 2 galaxies

We present spatially resolved BPT mapping of the extended narrow line regions (ENLRs) of seven nearby Seyfert 2 galaxies, using HST narrow band filter imaging. We construct the BPT diagrams using $\leq$ 0.1" resolution emission line images of [O III]$λ$5007, H$α$, [S II]$λ$$λ$6717,6731, and H$β$. By mapping these diagnostic lines according to the BPT classification, we dissect the ENLR into Seyfert, LINER, and star-forming regions. The nucleus and ionization cones are dominated by Seyfert-type emission, which can be interpreted as predominantly photoionization by the active galactic nucleus (AGN). The Seyfert nucleus and ionization cones transition to and are surrounded by a LINER cocoon, extending up to $\sim$ 250 pc in thickness. The ubiquity of the LINER cocoon in Seyfert 2 galaxies suggests that the circumnuclear regions are not necessarily Seyfert-type, and LINER activity plays an important role in Seyfert 2 galaxies. We demonstrate that spatially resolved diagnostics are crucial to understanding the excitation mechanisms in different regions and the AGN-host galaxy interactions.

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The Cepheid Distance to the Seyfert 1 Galaxy NGC 4151

We derive a distance of $15.8\pm0.4$ Mpc to the archetypical Seyfert 1 galaxy NGC 4151 based on the near-infrared Cepheid Period-Luminosity relation and new Hubble Space Telescope multiband imaging. This distance determination, based on measurements of 35 long-period ($P > 25$d) Cepheids, will support the absolute calibration of the supermassive black hole mass in this system, as well as studies of the dynamics of the feedback or feeding of its active galactic nucleus.

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A Catalog of 406 AGNs in MaNGA: A Connection between Radio-mode AGN and Star Formation Quenching

Accurate active galactic nucleus (AGN) identifications and spatially resolved host galaxy properties are a powerful combination for studies of the role of AGNs and AGN feedback in the coevolution of galaxies and their central supermassive black holes. Here, we present robust identifications of 406 AGNs in the first 6261 galaxies observed by the integral field spectroscopy survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA). Instead of using optical line flux ratios, which can be difficult to interpret in light of the effects of shocks and metallicity, we identify the AGNs via mid-infrared WISE colors, Swift/BAT ultra hard X-ray detections, NVSS and FIRST radio observations, and broad emission lines in SDSS spectra. We subdivide the AGNs into radio-quiet and radio-mode AGNs, and examine the correlations of the AGN classes with host galaxy star formation rates and stellar populations. When compared to the radio-quiet AGN host galaxies, we find that the radio-mode AGN host galaxies reside preferentially in elliptical galaxies, lie further beneath the star-forming main sequence (with lower star formation rates at fixed galaxy mass), have older stellar populations, and have more negative stellar age gradients with galactocentric distance (indicating inside-out quenching of star formation). These results establish a connection between radio-mode AGNs and the suppression of star formation.

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The OH Megamaser galaxy IRAS11506-3851: an AGN and starformation revealed by multiwavelength observations

We present Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the OH Megamaser (OHM) galaxy IRAS 11506-3851. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions and VLA data allow us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ~ 500 pc. While this ring shows starburst excitation and low velocity dispersion, the region internal to the ring shows higher excitation and velocity dispersion values, with values increasing towards its borders at ~ 240 pc from the nucleus, resembling a projected bubble. The enhanced excitation and velocity dispersion of this bubble surrounds a 8.5 GHz radio emission structure, supporting its origin in a faint AGN that is mostly shocking the surrounding gas via a plasma ejection seen in radio at the present stage. This is the fourth of the 5 OHM galaxies we have studied so far (from our sample of 15 OHM) for which GMOS-IFU data indicate the presence of a previously unknown faint AGN at the nucleus, consistent with the hypothesis that OHM galaxies harbor recently triggered AGN.

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Powerful ionized gas outflows in the interacting radio galaxy 4C +29.30

We investigate the ionized gas excitation and kinematics in the inner $4.3 \times 6.2$ kpc$^{2}$ of the merger radio galaxy 4C +29.30. Using optical integral field spectroscopy with the Gemini North Telescope, we present flux distributions, line-ratio maps, peak velocities and velocity dispersion maps as well as channel maps with a spatial resolution of $\approx 955$ pc. We observe high blueshifts of up to $\sim -650$ km s$^{-1}$, in a region $\sim 1''$ south of the nucleus (the southern knot, SK), which also presents high velocity dispersions ($\sim 250$ km s$^{-1}$), which we attribute to an outflow. A possible redshifted counterpart is observed north from the nucleus (the northern knot, NK). We propose that these regions correspond to a bipolar outflow possibly due to the interaction of the radio jet with the ambient gas. We estimate a total ionized gas mass outflow rate of $\dot{M}_{out} = 25.4 \substack{+11.5 \\ -7.5}$ M$_\odot$ yr$^{-1}$ with a kinetic power of $\dot{E} = 8.1 \substack{+10.7 \\ -4.0} \times 10^{42}$ erg s$^{-1}$, which represents $5.8 \substack{+7.6 \\ -2.9} \%$ of the AGN bolometric luminosity. These values are higher than usually observed in nearby active galaxies with the same bolometric luminosities and could imply a significant impact of the outflows in the evolution of the host galaxy. The excitation is higher in the NK (that correlates with extended X-ray emission, indicating the presence of hotter gas) than in the SK, supporting a scenario in which an obscuring dust lane is blocking part of the AGN radiation to reach the southern region of the galaxy.

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Ionized and hot molecular outflows in the inner 500 pc of NGC1275

The role of feedback from Active Galactic Nuclei (AGN) in the evolution of galaxies is still not not fully understood, mostly due to the lack of observational constraints in the multi-phase gas kinematics on the ten to hundred parsec scales. We have used the Gemini Near-infrared Integral Field Spectrograph (NIFS) to map the molecular and ionized gas kinematics in the inner 900$\times$900 pc$^2$ of the Seyfert galaxy NGC1275 at a spatial resolution of $\sim$70 pc. From the fitting of the CO absorption bandheads in the K-band, we derive a stellar velocity dispersion of $265\pm26$ km s$^{-1}$, which implies a black hole mass of $M_{\rm SMBH}=1.1^{+0.9}_{-0.5}\times10^9$ M$_\odot$. We find hot ($T\gtrsim1000$ K) molecular and ionized outflows with velocities of up to 2 000 km s$^{-1}$ and mass outflow rates of $2.7\times10^{-2} {\rm M_\odot}$ yr$^{-1}$ and $1.6 {\rm M_\odot}$ yr$^{-1}$, respectively, in each of these gas phases. The kinetic power of the ionized outflows corresponds to only 0.05 per cent of the luminosity of the AGN of NGC 1275, indicating that they are not powerful enough to provide significant AGN feedback, but may be effective in redistributing the gas in the central region of the galaxy. The AGN driven outflows seem to be responsible for the shocks necessary to produce the observed H$_2$ and [Fe II] line emission.

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LLAMA: The $M_{BH}$ - $σ_{\star}$ Relation of the most luminous local AGNs

The $M_{BH}$ - $σ_{\star}$ relation is considered a result of co-evolution between the host galaxies and their super-massive black holes. For elliptical-bulge hosting inactive galaxies, this relation is well established, but there is still a debate whether active galaxies follow the same relation. In this paper, we estimate black hole masses for a sample of 19 local luminous AGNs (LLAMA) in order to test their location on the $M_{BH}$ - $σ_{\star}$ relation. Super-massive black hole masses ($M_{BH}$) were derived from the broad-line based relations for H$α$, H$β$ and Pa$β$ emission line profiles for the Type 1 AGNs. We compare the bulge stellar velocity dispersion ($σ_{\star}$) as determined from the Ca II triplet (CaT) with the dispersion measured from the near-infrared CO (2-0) absorption features for each AGN and find them to be consistent with each other. We apply an extinction correction to the observed broad line fluxes and we correct the stellar velocity dispersion by an average rotation contribution as determined from spatially resolved stellar kinematic maps. The H$α$-based black hole masses of our sample of AGNs were estimated in the range 6.34 $\leq$ $\log{M_{BH}}$ $\leq$ 7.75 M$_\odot$ and the $σ_{\star CaT}$ estimates range between 73 $\leq$ $σ_{\star CaT}$ $\leq$ 227 km s$^{-1}$. From the so-constructed $M_{BH}$ - $σ_{\star}$ relation for our Type 1 AGNs, we estimate the black hole masses for the Type 2 AGNs and the inactive galaxies in our sample. In conclusion, we find that our sample of local luminous AGNs is consistent with the $M_{BH}$ - $σ_{\star}$ relation of lower luminosity AGNs and inactive galaxies, after correcting for dust extinction and the rotational contribution to the stellar velocity dispersion.

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A panchromatic spatially resolved study of the inner 500pc of NGC1052 -- II: Gas excitation and kinematics

We map the optical and near-infrared (NIR) emission-line flux distributions and kinematics of the inner 320$\times$535pc$^2$ of the elliptical galaxy NGC1052. The integral field spectra were obtained with the Gemini Telescope using the GMOS-IFU and NIFS instruments, with angular resolutions of 0''88 and 0''1 in the optical and NIR, respectively. We detect five kinematic components: (1 and 2) Two spatially unresolved components, being a broad line region visible in H$α$, with a FWHM of $\sim$3200km s$^{-1}$ and an intermediate-broad component seen in the [OIII]$λλ$4959,5007 doublet; (3) an extended intermediate-width component with 280<FWHM<450km s$^{-1}$ and centroid velocities up to 400km s$^{-1}$, which dominates the flux in our data, attributed either to a bipolar outflow related to the jets, rotation in an eccentric disc or a combination of a disc and large-scale gas bubbles; (4 and 5) two narrow (FWHM<150km s$^{-1}$) components, one visible in [OIII], and one visible in the other emission lines, extending beyond the field-of-view of our data, which is attributed to large-scale shocks. Our results suggest that the ionization within the observed field of view cannot be explained by a single mechanism, with photoionization being the dominant mechanism in the nucleus with a combination of shocks and photoionization responsible for the extended ionization.

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Outflows, Inflows and Young Stars in the inner 200 pc of the Seyfert galaxy NGC 2110

We present a two-dimensional mapping of stellar population age components, emission-line fluxes, gas excitation and kinematics within the inner $\sim200$ pc of the Seyfert 2 galaxy NGC 2110. We used the Gemini North Integral Field Spectrograph (NIFS) in the J and K bands at a spatial resolution of $\sim22$ pc. The unresolved nuclear continuum is originated in combined contributions of young stellar population (SP; age$\leq100$ Myr), a featureless AGN continuum and hot dust emission. The young-intermediate SP ($100<$age$\leq700$ Myr) is distributed in a ring-shaped structure at $\approx140$ pc from the nucleus, which is roughly coincident with the lowest values of the stellar velocity dispersion. In the inner $\approx115$ pc the old SP (age$>2$ Gyr) is dominant. The [FeII]1.25$μ$m emission-line flux distribution is correlated with the radio emission and its kinematics comprise two components, one from gas rotating in the galaxy plane and another from gas in outflow within a bicone oriented along north-south. These outflows seem to originate in the interaction of the radio jet with the ambient gas producing shocks that are the main excitation mechanism of the [FeII] emission. We estimate: (1) an ionized gas mass outflow rate of $\sim0.5$ M$_\odot$/yr at $\sim$70 pc from the nucleus; and (2) a kinetic power for the outflow of only 0.05% of the AGN bolometric luminosity implying weak feedback effect on the galaxy.

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