Abstract
Spatially resolved velocity maps at high resolutions of 1–10 pc are becoming available for many nearby active galactic nuclei (AGNs) in both optical/infrared atomic emission lines and ...submillimeter molecular lines. For the former, it is known that a linear relationship appears to exist between the velocity of the ionized gas clouds and the distance from the nucleus in the inner ∼100 pc region, where these clouds are outflowing. Here we demonstrate that, in such a case, we can actually derive the three-dimensional (3D) geometrical distribution of the clouds directly from the velocity map. Revisiting such a velocity map taken by the Hubble Space Telescope for the prototypical Type 2 AGN NGC 1068, we implement the visualization of the 3D distribution derived from the map, and show that this inner narrow-line region has indeed a hollow-cone structure, consistent with previous modeling results. Quite possibly, this is the outer extended part of the polar elongated dusty material seen in the recent mid-infrared interferometry at parsec scale. Conversely, the latter small-scale geometry is inferred to have a hollow-cone outflowing structure as the inward extension of the derived 3D distribution above. The AGN obscuring “torus” is argued to be the inner optically thick part of this hollow-cone outflow, and its shadowed side would probably be associated with the molecular outflow seen in certain submillimeter lines. We discuss the nature of the linear velocity field, which could be from an episodic acceleration that occurred ∼10
5
yr ago.
Context. With infrared interferometry it is possible to resolve the nuclear dust distributions that are commonly associated with the dusty torus in active galactic nuclei (AGN). The Circinus galaxy ...hosts the closest Seyfert 2 nucleus and previous interferometric observations have shown that its nuclear dust emission is particularly well resolved. Aims. The aim of the present interferometric investigation is to better constrain the dust morphology in this active nucleus. Methods. To this end, extensive new observations were carried out with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer, leading to a total of 152 correlated flux spectra and differential phases between 8 and 13 μm. To interpret this data, we used a model consisting of black-body emitters with a Gaussian brightness distribution and with dust extinction. Results. The direct analysis of the data and the modelling confirm that the emission is distributed in two distinct components: a disk-like emission component with a size (FWHM) of ~0.2 × 1.1 pc and an extended component with a size of ~0.8 × 1.9 pc. The disk-like component is elongated along PA ~ 46° and oriented perpendicular to the ionisation cone and outflow. The extended component is responsible for 80% of the mid-infrared emission. It is elongated along PA ~ 107°, which is roughly perpendicular to the disk component and thus in polar direction. It is interpreted as emission from the inner funnel of an extended dust distribution and shows a strong increase in the extinction towards the south-east. We find both emission components to be consistent with dust at T ~ 300 K, that is we find no evidence of an increase in the temperature of the dust towards the centre. From this we infer that most of the near-infrared emission probably comes from parsec scales as well. We further argue that the disk component alone is not sufficient to provide the necessary obscuration and collimation of the ionising radiation and outflow. The material responsible for this must instead be located on scales of ~1 pc, surrounding the disk. We associate this material with the dusty torus. Conclusions. The clear separation of the dust emission into a disk-like emitter and a polar elongated source will require an adaptation of our current understanding of the dust emission in AGN. The lack of any evidence of an increase in the dust temperature towards the centre poses a challenge for the picture of a centrally heated dust distribution.
Abstract
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 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
μ
m is unresolved at all available baseline lengths. The remaining 35% is partially resolved and shows angular structure. From geometric modeling, we find that the emission is elongated along a position angle of 155° ± 14° with an axis ratio (major/minor) of 2.9 ± 0.3. Because the system axis is oriented in the position angle 174° ± 2°, we conclude that the dust emission of this object is also polar extended. A
CAT3D-WIND
radiative transfer model of a dusty disk and a dusty wind with a half opening angle of 30° 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.
The active galaxy NGC 4151 has a crucial role as one of only two active galactic nuclei for which black hole mass measurements based on emission line reverberation mapping can be calibrated against ...other dynamical techniques. Unfortunately, effective calibration requires accurate knowledge of the distance to NGC 4151, which is not at present available. Recently reported distances range from 4 to 29 megaparsecs. Strong peculiar motions make a redshift-based distance very uncertain, and the geometry of the galaxy and its nucleus prohibit accurate measurements using other techniques. Here we report a dust-parallax distance to NGC 4151 of 19.0(+2.4)(-2.6) megaparsecs. The measurement is based on an adaptation of a geometric method that uses the emission line regions of active galaxies. Because these regions are too small to be imaged with present technology, we use instead the ratio of the physical and angular sizes of the more extended hot-dust emission as determined from time delays and infrared interferometry. This distance leads to an approximately 1.4-fold increase in the dynamical black hole mass, implying a corresponding correction to emission line reverberation masses of black holes if they are calibrated against the two objects with additional dynamical masses.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The dichotomy between radio-loud (RL) and radio-quiet (RQ) active galactic nuclei (AGNs) is thought to be intrinsically related to radio jet production. This difference may be explained by ...the presence of a strong magnetic field (
B
-field) that enhances, or is the cause of, the accretion activity and the jet power. Here we report the first evidence of an intrinsic difference in the polarized dust emission cores of four RL and five RQ obscured AGNs using 89
μ
m polarization with SOFIA/HAWC+. We find that the thermal polarized emission increases with the nuclear radio-loudness,
R
20
=
L
5GHz
/
L
20
μ
m
. The dust emission cores of RL AGNs are measured to be polarized, ∼5%–11%, while RQ AGNs are unpolarized, <1%. For RQ AGNs, our results are consistent with the observed region being filled with an unmagnetized or highly turbulent disk and/or expanding outflow at scales of 5–130 pc from the AGNs. For RL AGNs, the measured 89
μ
m polarization arises primarily from magnetically aligned dust grains associated with a 5–130 pc scale dusty obscuring structure with a toroidal
B
-field orientation highly offset, 65° ± 22°, with respect to the jet axis. Our results indicate that the size and strength of the
B
-fields surrounding the AGNs are intrinsically related to the strength of the jet power—the stronger the jet power is, the larger and stronger the toroidal
B
-field is. The detection of a ≤130 pc scale ordered toroidal
B
-field suggests that (a) the infalling gas that fuels RL AGNs is magnetized, (b) there is a magnetohydrodynamic wind that collimates the jet, and/or (c) the jet is able to magnetize its surroundings.
Abstract
Infrared interferometry of the local active galactic nucleus (AGN) has revealed a warm (∼300–400 K) polar dust structure that cannot be trivially explained by the putative dust torus of the ...unified model. This led to the development of the disk+wind scenario which comprises a hot (∼1000 K) compact equatorial dust disk and a polar dust wind. This wind is assumed to be driven by radiation pressure and, therefore, we would expect that long-term variation in radiation pressure would influence the dust distribution. In this paper we attempt to quantify if and how the dust distribution changes with radiation pressure. We analyze so far unpublished Very Large Telescope Interferometer (VLTI)/MID-infrared Interferometer (MIDI) data on 8 AGN and use previous results on 25 more to create a sample of 33 AGN. This sample comprises all AGN successfully observed with VLTI/MIDI. For each AGN, we calculate the Eddington ratio, using the intrinsic 2–10 keV X-ray luminosity and black hole mass, and compare this to the resolved dust emission fraction as seen by MIDI. We tentatively conclude that there is more dust in the wind at higher Eddington ratios, at least in type 2 AGN where such an effect is expected to be more easily visible.
Resolving the Hot Dust Disk of ESO323-G77 Leftley, James H.; Tristram, Konrad R. W.; Hönig, Sebastian F. ...
Astrophysical journal/The Astrophysical journal,
05/2021, Letnik:
912, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Infrared interferometry has led to a paradigm shift in our understanding of the dusty structure in the central parsecs of active galactic nuclei (AGNs). The dust is now thought to comprise a ...hot (∼1000 K) equatorial disk, some of which is blown into a cooler (∼300 K) polar dusty wind by radiation pressure. In this paper, we utilize the new near-IR interferometer GRAVITY on the Very Large Telescope Interferometer (VLTI) to study a Type 1.2 AGNs hosted in the nearby Seyfert galaxy ESO 323-G77. By modeling 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 spectral energy distribution of ESO 323-G77 and observations in the mid-IR from VLTI/MID-infrared Interferometric instrument).
The taxonomy and phylogeny of the subgenus Mus, the Eurasian lineage of the genus Mus, remain unresolved, even for the house mouse (Mus musculus). While the subgenus is diverse in Asia, few studies ...cover both its morphology and molecular phylogeny. We re-examined 70 specimens identified as M. cervicolor that were collected from central Nepal in 1968 and 1975 and are currently deposited in the Hokkaido University Natural History Museum. To compare morphological features, we examined skull geometric morphometrics and body coloration, and performed a phylogenetic analysis of the mitochondrial cytochrome b gene sequences of representative specimens. The specimens were most likely either M. booduga or M. musculus. The best morphological characteristics for distinguishing the two species were the nasal length ratio, which was high and low, respectively. Mus booduga was found to inhabit altitudes lower than 1000 m and have light ventral fur, while M. musculus inhabited various altitudes up to 3000 m and had variable fur color depending on the altitude. We also discuss the taxonomic status of the fawn-colored mouse M. cervicolor.
Abstract
The nuclear region of Type 1 active galactic nuclei (AGNs) has only been partially resolved so far in the near-infrared (IR), where we expect to see the dust sublimation region and the ...nucleus directly without obscuration. Here, we present the near-IR interferometric observation of the brightest Type 1 AGN NGC 4151 at long baselines of ∼250 m using the CHARA Array, reaching structures at hundred microarcsecond scales. The squared visibilities decrease down to as low as ∼0.25, definitely showing that the structure is resolved. Furthermore, combining with the previous visibility measurements at shorter baselines but at different position angles, we show that the structure is elongated
perpendicular
to the polar axis of the nucleus, as defined by optical polarization and a linear radio jet. A thin-ring fit gives a minor/major axis ratio of ∼0.7 at a radius ∼0.5 mas (∼0.03 pc). This is consistent with the case where the sublimating dust grains are distributed preferentially in the equatorial plane in a ring-like geometry, viewed at an inclination angle of ∼40°. The recent mid-IR interferometric finding of polar-elongated geometry at a pc scale, together with a larger-scale polar outflow as spectrally resolved by the Hubble Space Telescope, would generally suggest a dusty, conical and hollow outflow being launched, presumably in the dust sublimation region. This might potentially lead to a polar-elongated morphology in the near-IR, as opposed to the results here. We discuss a possible scenario where an episodic, one-off anisotropic acceleration formed a polar-fast and equatorially slow velocity distribution, having led to an effectively flaring geometry as we observe.
Quasars are thought to be powered by supermassive black holes accreting surrounding gas. Central to this picture is a putative accretion disk which is believed to be the source of the majority of the ...radiative output. It is well known, however, that the most extensively studied disk model-an optically thick disk which is heated locally by the dissipation of gravitational binding energy-is apparently contradicted by observations in a few major respects. In particular, the model predicts a specific blue spectral shape asymptotically from the visible to the near-infrared, but this is not generally seen in the visible wavelength region where the disk spectrum is observable. A crucial difficulty has been that, towards the infrared, the disk spectrum starts to be hidden under strong, hot dust emission from much larger but hitherto unresolved scales, and thus has essentially been impossible to observe. Here we report observations of polarized light interior to the dust-emitting region that enable us to uncover this near-infrared disk spectrum in several quasars. The revealed spectra show that the near-infrared disk spectrum is indeed as blue as predicted. This indicates that, at least for the outer near-infrared-emitting radii, the standard picture of the locally heated disk is approximately correct.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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