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Register a new userNew evidence for the dusty wind model: Polar dust and a hot core in the type-1 Seyfert ESO$,$323-G77
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Infrared interferometry of Seyfert galaxies has revealed that their warm ($300-400,$K) dust emission originates primarily from polar regions instead of from an equatorial dust torus as predicted by the classic AGN unification scheme. We present new data for the type 1.2 object ESO$,$323-G77 obtained with the MID-infrared interferometric Instrument (MIDI) and a new detailed morphological study of its warm dust. The partially resolved emission on scales between $5$ and $50,$mas ($1.6-16,$pc) is decomposed into a resolved and an unresolved source. Approximately $65%$ of the correlated flux between $8$ and $13,mumathrm{m}$ is unresolved at all available baseline lengths. The remaining $35%$ is partially resolved and shows angular structure. From geometric modelling we find that the emission is elongated along a position angle of $155^circpm14^circ$ with an axis ratio (major/minor) of $2.9pm0.3$. Because the system axis is oriented in position angle $174^circpm2^circ$, we conclude that the dust emission of this object is also polar extended. A $textit{CAT3D-WIND}$ radiative transfer model of a dusty disk and a dusty wind with a half opening angle of $30^circ$ can reproduce both the interferometric data and the SED, while a classical torus model is unable to fit the interferometric data. We interpret this as further evidence that a polar dust component is required even for low-inclination type 1 sources.
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Infrared interferometry has fuelled a paradigm shift in our understanding of the dusty structure in the central parsecs of Active Galactic Nuclei (AGN). The dust is now thought to comprise of a hot ($sim1000,$K) equatorial disk, some of which is blown into a cooler ($sim300,$K) polar dusty wind by radiation pressure. In this paper, we utilise the new near-IR interferometer GRAVITY on the Very Large Telescope Interferometer (VLTI) to study a Type 1.2 AGN hosted in the nearby Seyfert galaxy ESO323-G77. By modelling the squared visibility and closure phase, we find that the hot dust is equatorially extended, consistent with the idea of a disk, and shows signs of asymmetry in the same direction. Furthermore, the data is fully consistent with the hot dust size determined by K band reverberation mapping as well as the predicted size from a CAT3D-WIND model created in previous work using the SED of ESO323-G77 and observations in the mid-IR from VLTI/MIDI.
The key ingredient of active galactic nuclei (AGN) unification, the dusty obscuring torus was so far held responsible for the observed mid-infrared (MIR) emission of AGN. However, the best studied objects with VLTI/MIDI show that instead a polar dusty wind is dominating these wavelengths, leaving little room for a torus contribution. But is this wind an ubiquitous part of the AGN? To test this, we conducted a straightforward detection experiment, using the upgraded VLT/VISIR for deep subarcsecond resolution MIR imaging of a sample of nine [O IV]-bright, obscured AGN, all of which were predicted to have detectable polar emission. Indeed, the new data reveal such emission in all objects but one. We further estimate lower limits on the extent of the polar dust and show that the polar dust emission is dominating the total MIR emission of the AGN. These findings support the scenario that polar dust is not only ubiquitous in AGN but also an integral part of its structure, processing a significant part of the primary radiation. The polar dust has to be optically thin on average, which explains, e.g., the small dispersion in the observed mid-infrared--X-ray luminosity correlation. At the same time, it has to be taken into account when deriving covering factors of obscuring material from mid-infrared to bolometric luminosity ratios. Finally, we find a new tentative trend of increasing MIR emission size with increasing Eddington ratio.
I Zwicky 1 is the prototype optical narrow line Seyfert 1 galaxy. It is also a nearby ($z=0.0611$), luminous QSO, accreting close to the Eddington limit. XMM-Newton observations of I Zw 1 in 2015 reveal the presence of a broad and blueshifted P-Cygni iron K profile, as observed through a blue-shifted absorption trough at 9 keV and a broad excess of emission at 7 keV in the X-ray spectra. The profile can be well fitted with a wide angle accretion disk wind, with an outflow velocity of at least $-0.25c$. In this respect, I Zw 1 may be an analogous to the prototype fast wind detected in the QSO, PDS 456, while its overall mass outflow rate is scaled down by a factor $times50$ due to its lower black hole mass. The mechanical power of the fast wind in I Zw 1 is constrained to within $5-15$% of Eddington, while its momentum rate is of the order unity. Upper-limits placed on the energetics of any molecular outflow, from its CO profile measured by IRAM, appear to rule out the presence of a powerful, large scale, energy conserving wind in this AGN. We consider whether I Zw 1 may be similar to a number of other AGN, such as PDS 456, where the large scale galactic outflow is much weaker than what is anticipated from models of energy conserving feedback.
The famous Rosette Nebula has an evacuated central cavity formed from the stellar winds ejected from the 2-6 million-year-old co-distant and co-moving central star cluster NGC 2244. However, with upper age estimates of less than 110,000 years, the central cavity is too young compared to NGC 2244 and existing models do not reproduce its properties. A new proper motion study herein using Gaia data reveals the ejection of the most massive star in the Rosette, HD46223, from NGC 2244 occurred 1.73 (+0.34,-0.25)Myr (1$sigma$ uncertainty) in the past. Assuming this ejection was at the birth of the most massive stars in NGC 2244, including the dominant centrally positioned HD46150, the age is set for the famous ionised region at more than ten times that derived for the cavity. Here, we are able to reproduce the structure of the Rosette Nebula, through simulation of mechanical stellar feedback from a 40M$_{odot}$ star in a thin sheet-like molecular cloud. We form the 135,000M$_{odot}$ cloud from thermally-unstable diffuse interstellar medium under the influence of a realistic background magnetic field with thermal/magnetic pressure equilibrium. Properties derived from a snapshot of the simulation at 1.5Myr, including cavity size, stellar age, magnetic field and resulting inclination to the line of sight, match those derived from observations. An elegant explanation is thus provided for the stark contrast in age estimates based on realistic diffuse ISM properties, molecular cloud formation and stellar wind feedback.
We present sensitive high angular resolution submillimeter and millimeter observations of torsionally/vibrationally highly excited lines of the CH$_3$OH, HC$_3$N, SO$_2$, and CH$_3$CN molecules and of the continuum emission at 870 and 1300 $mu$m from the Orion KL region, made with the Submillimeter Array (SMA). These observations plus recent SMA CO J=3-2 and J=2-1 imaging of the explosive flow originating in this region, which is related to the non-hierarchical disintegration of a massive young stellar system, suggest that the molecular Orion Hot Core is a pre-existing density enhancement heated from the outside by the explosive event -- unlike in other hot cores we do not find any self-luminous submillimeter, radio or infrared source embedded in the hot molecular gas. Indeed, we do not observe filamentary CO flow structures or fingers in the shadow of the hot core pointing away from the explosion center. The low-excitation CH$_3$CN emission shows the typical molecular heart-shaped structure, traditionally named the Hot Core, and is centered close to the dynamical origin of the explosion. The highest excitation CH$_3$CN lines are all arising from the northeast lobe of the heart-shaped structure, {it i. e.} from the densest and most highly obscured parts of the Extended Ridge. The torsionally excited CH$_3$OH and vibrationally excited HC$_3$N lines appear to form a shell around the strongest submillimeter continuum source. Surprisingly the kinematics of the Hot Core and Compact Ridge regions as traced by CH$_3$CN and HC$_3$N also reveal filament-like structures that emerge from the dynamical origin. All of these observations suggest the southeast and southwest sectors of the explosive flow to have impinged on a pre-existing very dense part of the Extended Ridge, thus creating the bright Orion KL Hot Core.
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