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Register a new userDisk Outflows and High-Luminosity True Type 2 AGN
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The absence of intrinsic broad line emission has been reported in a number of active galactic nuclei (AGN), including some with high Eddington ratios. Such true type 2 AGN are inherent to the disk-wind scenario for the broad line region: Broad line emission requires a minimal column density, implying a minimal outflow rate and thus a minimal accretion rate. Here we perform a detailed analysis of the consequences of mass conservation in the process of accretion through a central disk. The resulting constraints on luminosity are consistent with all the cases where claimed detections of true type 2 AGN pass stringent criteria, and predict that intrinsic broad line emission can disappear at luminosities as high as about 4x$10^{46}$ erg s$^{-1}$ and any Eddington ratio, though more detections can be expected at Eddington ratios below about 1%. Our results are applicable to every disk outflow model, whatever its details and whether clumpy or smooth, irrespective of the wind structure and its underlying dynamics. While other factors, such as changes in spectral energy distribution or covering factor, can affect the intensities of broad emission lines, within this scenario they can only produce true type 2 AGN of higher luminosity then those prescribed by mass conservation.
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We study outflows driven by Active Galactic Nuclei (AGNs) using high- resolution simulations of idealized z=2 isolated disk galaxies. Episodic accretion events lead to outflows with velocities >1000 km/s and mass outflow rates up to the star formation rate (several tens of Msun/yr). Outflowing winds escape perpendicular to the disk with wide opening angles, and are typically asymmetric (i.e. unipolar) because dense gas above or below the AGN in the resolved disk inhibits outflow. Owing to rapid variability in the accretion rates, outflowing gas may be detectable even when the AGN is effectively off. The highest velocity outflows are sometimes, but not always, concentrated within 2-3 kpc of the galactic center during the peak accretion. With our purely thermal AGN feedback model -- standard in previous literature -- the outflowing material is mostly hot (10^6 K) and diffuse (nH<10^(-2) cm-3), but includes a cold component entrained in the hot wind. Despite the powerful bursts and high outflow rates, AGN feedback has little effect on the dense gas in the galaxy disk. Thus AGN-driven outflows in our simulations do not cause rapid quenching of star-formation, although they may remove significant amounts of gas of long (>Gyr) timescales.
We present a detailed study of ionized outflows in a large sample of ~650 hard X-ray detected AGN. Using optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS) we are able to reveal the faint wings of the [OIII] emission lines associated with outflows covering, for the first time, an unexplored range of low AGN bolometric luminosity at low redshift (z~0.05). We test if and how the incidence and velocity of ionized outflow is related to AGN physical parameters: black hole mass, gas column density, Eddington Ratio, [OIII], X-ray, and bolometric luminosities. We find a higher occurrence of ionized outflows in type 1.9 (55%) and type 1 AGN (46%) with respect to type 2 AGN (24%). While outflows in type 2 AGN are evenly balanced between blue and red velocity offsets with respect to the [OIII] narrow component, they are almost exclusively blueshifted in type 1 and type 1.9 AGN. We observe a significant dependence between the outflow occurrence and accretion rate, which becomes relevant at high Eddington ratios (> -1.7). We interpret such behaviour in the framework of covering factor-Eddington ratio dependence. We dont find strong trends of the outflow maximum velocity with AGN physical parameters, as an increase with bolometric luminosity can be only identified when including samples of AGN at high luminosity and high redshift taken from literature.
In the manuscript, the composite galaxy SDSS J103911-000057 (=SDSS J1039) is reported as a better candidate of true Type-2 AGN without hidden BLRs. None broad but only narrow emission lines detected in SDSS J1039 can be well confirmed both by the F-test technique and by the expected broad emission lines with EW smaller than 13.5AA~ with 99% confidence level. Meanwhile, a reliable AGN power law component is preferred with confidence level higher than 7sigma in SDSS J1039. Furthermore, the long-term variability of SDSS J1039 from CSS can be well described by the DRW process with intrinsic variability timescale $tausim100{rm days}$, similar as normal quasars. And, based on BH mass in SDSS J1039 through the msig relation and on the correlation between AGN continuum luminosity and total H$alpha$ luminosity, the expected broad H$alpha$, if there was, could be re-constructed with line width about $300-1000{rm km~s^{-1}}$ and with line flux about $666times10^{-17}{rm erg~s^{-1}~cm^{-2}}$ under the Virialization assumption to BLRs, providing robust evidence to reject the probability that the intrinsic probable broad H$alpha$ were overwhelmed by noises of the SDSS spectrum in SDSS J1039. Moreover, the SDSS J1039 does follow the same correlation between continuum luminosity and [O~{sc iii}] line luminosity as the one for normal broad line AGN, indicating SDSS J1039 classified as a changing-look AGN at dim state can be well ruled out. Therefore, under the current knowledge, SDSS J1039 is a better candidate of true Type-2 AGN.
Feedback from active galactic nuclei (AGN) on their host galaxies, in the form of gas outflows capable of quenching star formation, is considered a major player in galaxy evolution. However, clear observational evidence of such major impact is still missing; uncertainties in measuring outflow properties might be partly responsible because of their critical role in comparisons with models and in constraining the impact of outflows on galaxies. Here we briefly review the challenges in measuring outflow physical properties and present an overview of outflow studies from high to low redshift. Finally, we present highlights from our MAGNUM survey of nearby AGN with VLT/MUSE, where the high intrinsic spatial resolution (down to $sim$10 pc) allows us to accurately measure the physical and kinematic properties of ionised gas outflows.
We investigate the process of rapid star formation quenching in a sample of 12 massive galaxies at intermediate redshift (z~0.6) that host high-velocity ionized gas outflows (v>1000 km/s). We conclude that these fast outflows are most likely driven by feedback from star formation rather than active galactic nuclei (AGN). We use multiwavelength survey and targeted observations of the galaxies to assess their star formation, AGN activity, and morphology. Common attributes include diffuse tidal features indicative of recent mergers accompanied by bright, unresolved cores with effective radii less than a few hundred parsecs. The galaxies are extraordinarily compact for their stellar mass, even when compared with galaxies at z~2-3. For 9/12 galaxies, we rule out an AGN contribution to the nuclear light and hypothesize that the unresolved core comes from a compact central starburst triggered by the dissipative collapse of very gas-rich progenitor merging disks. We find evidence of AGN activity in half the sample but we argue that it accounts for only a small fraction (<10%) of the total bolometric luminosity. We find no correlation between AGN activity and outflow velocity and we conclude that the fast outflows in our galaxies are not powered by on-going AGN activity, but rather by recent, extremely compact starbursts.
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