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Register a new userKiloparsec-scale AGN Outflows and Feedback in Merger-Free Galaxies
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Recent observations and simulations have challenged the long-held paradigm that mergers are the dominant mechanism driving the growth of both galaxies and supermassive black holes (SMBH), in favour of non-merger (secular) processes. In this pilot study of merger-free SMBH and galaxy growth, we use Keck Cosmic Web Imager spectral observations to examine four low-redshift ($0.043 < z < 0.073$) disk-dominated `bulgeless galaxies hosting luminous AGN, assumed to be merger-free. We detect blueshifted broadened [OIII] emission from outflows in all four sources, which the oiii/hbeta~ratios reveal are ionised by the AGN. We calculate outflow rates in the range $0.12-0.7~rm{M}_{odot}~rm{yr}^{-1}$, with velocities of $675-1710~rm{km}~rm{s}^{-1}$, large radial extents of $0.6-2.4~rm{kpc}$, and SMBH accretion rates of $0.02-0.07~rm{M}_{odot}~rm{yr}^{-1}$. We find that the outflow rates, kinematics, and energy injection rates are typical of the wider population of low-redshift AGN, and have velocities exceeding the galaxy escape velocity by a factor of $sim30$, suggesting that these outflows will have a substantial impact through AGN feedback. Therefore, if both merger-driven and non-merger-driven SMBH growth lead to co-evolution, this suggests that co-evolution is regulated by feedback in both scenarios. Simulations find that bars and spiral arms can drive inflows to galactic centres at rates an order of magnitude larger than the combined SMBH accretion and outflow rates of our four targets. This work therefore provides further evidence that non-merger processes are sufficient to fuel SMBH growth and AGN outflows in disk galaxies.
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The most accepted scenario for the evolution of massive galaxies across cosmic time predicts a regulation based on the interplay between AGN feedback, which injects large amounts of energy in the host environment, and galaxy mergers, being able to trigger massive star formation events and accretion onto the supermassive black holes. Interacting systems hosting AGN are useful laboratories to get key insights into both phenomena. In this context, we present the analysis of the optical spectral properties of IRAS 20210+1121 (I20210), a merging system at $z = 0.056$. According to X-ray data, this object comprises two interacting galaxies, each hosting an obscured AGN. The optical spectra confirm the presence of AGN features in both galaxies. In particular, we are able to provide a Seyfert classification for I20210 North. The spectrum of I20120 South shows broad blueshifted components associated with the most intense emission lines that indicate the presence of an ionized outflow, for which we derive a maximum velocity of $sim$2000 km s$^{-1}$, an extension of $sim$2 kpc and a mass rate of $sim$0.6 M$_odot$ yr$^{-1}$. We also report the existence of an ionized nebular component with $v sim 1000$ km s$^{-1}$ at $sim$6.5 kpc Southwards of I20210 South, that can be interpreted as disrupted gas ejected from the host galaxy by the action of the outflow. I20120 therefore exhibits a double obscured AGN, with one of them showing evidence of ongoing events for AGN-powered outflows. Future spatially-resolved spectroscopy will allow to accurately map on the gas kinematics in this AGN pair and evaluate the impact of the outflow on both the interstellar medium and galaxy environment.
The prevalence and properties of kiloparsec-scale outflows in nearby Type 1 quasars have been the subject of little previous attention. This work presents Gemini integral field spectroscopy of ten Type 1 radio-quiet quasars at $z<0.3$. The excellent image quality, coupled with a new technique to remove the point spread function using spectral information, allow the fitting of the underlying host on a spaxel-by-spaxel basis. Fits to stars, line-emitting gas, and interstellar absorption show that 100% of the sample host warm ionized and/or cool neutral outflows with spatially-averaged velocities ($langle v_{98%}rangle equiv langle v+2sigmarangle$) of 200-1300 km/s and peak velocities (maximum $v_{98%}$) of 500-2600 km/s. These minor-axis outflows are powered primarily by the central AGN, reach scales of 3-12 kpc, and often fill the field of view. Including molecular data and Type 2 quasar measurements, nearby quasars show a wide range in mass outflow rates ($dM/dt = 1$ to $>$1000 M$_odot$/yr) and momentum boosts [($c$ $dp/dt$)/L$_mathrm{AGN}$ = 0.01-20]. After extending the mass scale to Seyferts, $dM/dt$ and $dE/dt$ correlate with black hole mass ($dM/dt sim M_mathrm{BH}^{0.7pm0.3}$ and $dE/dt sim M_mathrm{BH}^{1.3pm0.5}$). Thus, the most massive black holes in the local universe power the most massive and energetic quasar-mode winds.
We employ optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with X-ray and radio data to study the highly-ionized gas (HIG) phase of the feedback in a sample of five local nearby Active Galactic Nuclei (AGN). Thanks to the superb field of view and sensitivity of MUSE, we found that the HIG, traced by the coronal line [FeVII] $lambda$6089, extends to scales not seen before, from 700 pc in Circinus and up to ~2 kpc in NGC5728 and NGC3393. The gas morphology is complex, following closely the radio jet and the X-ray emission. Emission line ratios suggest gas excitation by shocks produced by the passage of the radio jet. This scenario is further supported by the physical conditions derived for the HIG, stressing the importance of the mechanical feedback in AGN with low-power radio jets.
We present a spatially-resolved analysis of ionized and molecular gas in a nearby Seyfert 2 galaxy NGC 5728, using the VLT/MUSE and ALMA data. We find ionized gas outflows out to ~kpc scales, which encounter the star formation ring at 1 kpc radius. The star formation rate of the encountering region is significantly high (~1.8 M$_{rm sol}/yr/kpc^2$) compared to other regions in the ring. In contrast, the CO (2-1) emission is significantly weaker by a factor of ~3.5, indicating very high star formation efficiency. These results support the positive feedback scenario that the AGN-driven outflows compress the ISM in the ring, enhancing the star formation activity. In addition, we detect outflow regions outside of spiral arms, in which gas is likely to be removed from the spiral arms and no clear sign of star formation is detected. The overall impact of AGN outflows on the global star formation in NGC 5728 is limited, suggesting the feedback of the low-luminosity AGN is insignificant.
Seyfert and LINER galaxies are known to exhibit compact radio emission on $sim$ 10 to 100 parsec scales, but larger Kiloparsec-Scale Radio structures (KSRs) often remain undetected in sub-arcsec high resolution observations. We investigate the prevalence and nature of KSRs in Seyfert and LINER galaxies using the 1.4 GHz VLA FIRST and NVSS observations. Our sample consists of 2651 sources detected in FIRST and of these 1737 sources also have NVSS counterparts. Considering the ratio of total to peak flux density ($theta$ $=$ ${rm (S_{rm int}/S_{rm peak})^{1/2}}$) as a parameter to infer the presence of extended radio emission we show that $geq$ 30$%$ of FIRST detected sources possess extended radio structures on scales larger than 1.0 kpc. The use of low-resolution NVSS observations help us to recover faint extended KSRs that are resolved out in FIRST observations and results in $geq$ 42.5$%$ KSR sources in FIRST-NVSS subsample. This fraction is only a lower limit owing to the combination of projection, resolution and sensitivity effects. Our study demonstrates that KSRs may be more common than previously thought and are found across all redshifts, luminosities and radio-loudness. The extranuclear radio luminosity of KSR sources is found to be positively correlated with the core radio luminosity as well as the [O~III] $lambda$5007{AA} line luminosity and this can be interpreted as KSRs being powered by AGN rather than star-formation. The distributions of the FIR-to-radio ratios and mid-IR colors of KSR sources are also consistent with their AGN origin. However, contribution from star-formation cannot be ruled out particularly in sources with low radio luminosities.
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