Using VLTI/GRAVITY and SINFONI data, we investigate the subparsec gas and dust structure around the nearby type 1 active galactic nucleus (AGN) hosted by NGC 3783. The
K
-band coverage of GRAVITY ...uniquely allows simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-infrared(near-IR)-continuum-emitting hot dust, and the size of the coronal line region (CLR). We find the BLR, probed through broad Br
γ
emission, to be well described by a rotating, thick disc with a radial distribution of clouds peaking in the inner region. In our BLR model, the physical mean radius of 16 light-days is nearly twice the ten-day time-lag that would be measured, which closely matches the ten-day time-lag that has been measured by reverberation mapping. We measure a hot dust full-width at half-maximum (FWHM) size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust, which reveals a faint (5% of the total flux) offset cloud that we interpret as an accreting or outflowing cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the Ca
VIII
and narrow Br
γ
line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01 to 100 pc.
We present new near-infrared VLTI/GRAVITY interferometric spectra that spatially resolve the broad Br
γ
emission line in the nucleus of the active galaxy IRAS 09149−6206. We use these data to measure ...the size of the broad line region (BLR) and estimate the mass of the central black hole. Using an improved phase calibration method that reduces the differential phase uncertainty to 0.05° per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ∼0.5° between the line and continuum. This represents an offset of ∼120
μ
as (0.14 pc) between the BLR and the centroid of the hot dust distribution traced by the 2.3
μ
m continuum. The offset is well within the dust sublimation region, which matches the measured ∼0.6 mas (0.7 pc) diameter of the continuum. A clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the Br
γ
line. We infer the radius of the BLR to be ∼65
μ
as (0.075 pc), which is consistent with the radius–luminosity relation of nearby active galactic nuclei derived based on the time lag of the H
β
line from reverberation mapping campaigns. Our dynamical modelling indicates the black hole mass is ∼1 × 10
8
M
⊙
, which is a little below, but consistent with, the standard
M
BH
–
σ
*
relation.
We present near-infrared interferometric data on the Seyfert 2 galaxy NGC 1068, obtained with the GRAVITY instrument on the European Southern Observatory Very Large Telescope Interferometer. The ...extensive baseline coverage from 5 to 60
M
λ
allowed us to reconstruct a continuum image of the nucleus with an unrivaled 0.2 pc resolution in the
K
-band. We find a thin ring-like structure of emission with a radius
r
= 0.24 ± 0.03 pc, inclination
i
= 70 ± 5°, position angle PA = −50 ± 4°, and
h
/
r
< 0.14, which we associate with the dust sublimation region. The observed morphology is inconsistent with the expected signatures of a geometrically and optically thick torus. Instead, the infrared emission shows a striking resemblance to the 22 GHz maser disc, which suggests they share a common region of origin. The near-infrared spectral energy distribution indicates a bolometric luminosity of (0.4–4.7) × 10
45
erg s
−1
, behind a large
A
K
≈ 5.5 (
A
V
≈ 90) screen of extinction that also appears to contribute significantly to obscuring the broad line region.
We use VLTI/GRAVITY near-infrared interferometry measurements of eight bright type 1 AGN to study the size and structure of hot dust that is heated by the central engine. We partially resolve each ...source, and report Gaussian full width at half-maximum sizes in the range 0.3−0.8 mas. In all but one object, we find no evidence for significant elongation or asymmetry (closure phases ≲1°). The narrow range of measured angular sizes is expected given the similar optical flux of our targets, and implies an increasing effective physical radius with bolometric luminosity, as found from previous reverberation and interferometry measurements. The measured sizes for Seyfert galaxies are systematically larger than for the two quasars in our sample when measured relative to the previously reported
R
∼
L
1/2
relationship, which is explained by emission at the sublimation radius. This could be evidence of an evolving near-infrared emission region structure as a function of central luminosity.
ABSTRACT
The way supermassive black holes (SMBHs) in Galactic Centres (GCs) accumulate their mass is not completely determined. At large scales, it is governed by galactic encounters, mass inflows ...connected to spirals arms and bars, or due to expanding shells from supernova (SN) explosions in the central parts of galaxies. The investigation of the latter process requires an extensive set of gas dynamical simulations to explore the multidimensional parameter space needed to frame the phenomenon. The aims of this paper are to extend our investigation of the importance of SNe for inducing accretion on to an SMBH and carry out a comparison between the fully hydrodynamic code flash and the much less computationally intensive code ring, which uses the thin shell approximation. We simulate 3D expanding shells in a gravitational potential similar to that of the GC with a variety of homogeneous and turbulent environments. In homogeneous media, we find convincing agreement between flash and ring in the shapes of shells and their equivalent radii throughout their whole evolution until they become subsonic. In highly inhomogeneous, turbulent media, there is also a good agreement of shapes and sizes of shells, and of the times of their first contact with the central 1-pc sphere, where we assume that they join the accretion flow. The comparison supports the proposition that an SN occurring at a galactocentric distance of 5 pc typically drives 1–3 M⊙ into the central 1 pc around the GC.
Context. The Very Large Telescope Interferometer (VLTI) has been providing breakthrough images of the dust in the central parsecs of active galactic nuclei (AGNs), which is thought to be a key ...component of the AGN unification scheme and AGN host galaxy interaction. In single infrared bands, these images can enjoin multiple interpretations, some of which could challenge the unification scheme. This is the case for the archetypal type 2 AGN of NGC 1068, whereby the degeneracy is reduced by multi-band temperature maps that are hindered by an ambiguity in the alignment between different single-band images. Aims. We aim to solve this problem by creating a chromatic model capable of simultaneously explaining the VLTI GRAVITY+MATISSE 2 μm–13 μm observations of AGNs hosted by NGC 1068. Methods. We employed a simple disk and wind geometry populated by spherical black-body emitters and dust obscuration to create a versatile multi-wavelength modelling method for chromatic IR interferometric data of dusty objects. Results. This simple geometry is capable of reproducing the spectro-interferometric data of NGC 1068 from the K through N bands. It explains the complex single band images with obscuration and inclination effects, and it solves the alignment problem between bands. We find that the resulting model disk and wind geometry is consistent with previous studies of comparable and larger scales. For example, compared to molecular gas emission, our model wind position angle (PA) of 23 2 2° is close to the mas-scale outflowing CO(6–5) PA of ∼33° seen with ALMA. The equivalent 90° offset model disk PA is also consistent with the CO(6–5) disk axis of 112° as well as the mas-scale disk axis from CO(2–1), CO(3–2), and HCO + (4–3) of 115 ± 5°. Furthermore, the resulting model images visually resemble the multiple achromatic image reconstructions of the same data when evaluated at the same wavelengths. We conclude that the IR emitting structure surrounding the AGN within NGC 1068 can indeed be explained by the clumpy disk+wind iteration of the AGN unification scheme. Within the scheme, we find that it is best explained as a type 2 AGN and the obscuring dust chemistry can be explained by a mix of olivine silicates and 16 ± 1% amorphous carbon.
The angular size of the broad line region (BLR) of the nearby active galactic nucleus NGC 3783 has been spatially resolved by recent observations with VLTI/GRAVITY. A reverberation mapping (RM) ...campaign has also recently obtained high quality light curves and measured the linear size of the BLR in a way that is complementary to the GRAVITY measurement. The size and kinematics of the BLR can be better constrained by a joint analysis that combines both GRAVITY and RM data. This, in turn, allows us to obtain the mass of the supermassive black hole in NGC 3783 with an accuracy that is about a factor of two better than that inferred from GRAVITY data alone. We derive
M
BH
= 2.54
−0.72
+0.90
× 10
7
M
⊙
. Finally, and perhaps most notably, we are able to measure a geometric distance to NGC 3783 of 39.9
−11.9
+14.5
Mpc. We are able to test the robustness of the BLR-based geometric distance with measurements based on the Tully–Fisher relation and other indirect methods. We find the geometric distance is consistent with other methods within their scatter. We explore the potential of BLR-based geometric distances to directly constrain the Hubble constant,
H
0
, and identify differential phase uncertainties as the current dominant limitation to the
H
0
measurement precision for individual sources.
How to create Sgr A East Ehlerová, S.; Palouš, J.; Morris, M. R. ...
Astronomy and astrophysics (Berlin),
12/2022, Volume:
668
Journal Article
Peer reviewed
Open access
Context.
Sgr A East is the supernova remnant closest to the centre of the Milky Way. Its age has been estimated to be either very young, around 1–2 kyr, or about 10 kyr, and its exact origin remains ...unclear.
Aims.
We aspire to create a simple model of a supernova explosion that reproduces the shape, size, and location of Sgr A East.
Methods.
Using a simplified hydrodynamical code, we simulated the evolution of a supernova remnant in the medium around the Galactic centre. The latter consists of a nearby massive molecular cloud with which Sgr A East is known to be interacting and a wind from the nuclear star cluster.
Results.
Our preferred models of the Sgr A East remnant are compatible with an age of around 10 kyr. We also find suitable solutions for older ages, but not for ages younger than 5 kyr. Our simulations predict that the supernova exploded at a distance of about 3.5 pc from the Galactic centre, below the Galactic plane, slightly eastwards from the centre and 3 pc behind it.
Context.
The central region of NGC 1068 is one of the closest and most studied active galactic nuclei. It is known to be type 2, meaning that its accretion disk is obscured by a large amount of dust ...and gas. The main properties of the obscuring structure are still to be determined.
Aims.
We aim to model the inner edge of this structure, where the hot dust responsible for the near-infrared emission reaches its sublimation temperature.
Methods.
We used several methods to interpret the
K
-band interferometric observables from a GRAVITY/VLTI observation of the object. At first, we used simple geometrical models in image reconstructions to determine the main 2D geometrical properties of the source. In a second step, we tried to reproduce the observables with
K
-band images produced by 3D radiative transfer simulations of a heated dusty disk. We explore various parameters to find an optimal solution and a model consistent with all the observables.
Results.
The three methods are consistent in their description of the image of the source, an elongated structure with ∼4 × 6 mas dimensions and its major axis along the northwest–southeast direction. The results from all three methods suggest that the object resembles an elongated ring rather than an elongated thin disk, with the northeast edge appearing less luminous than the southwest one. The best 3D model is a thick disk with an inner radius
r
= 0.21
−0.03
+0.02
pc and a half-opening angle
α
1/2
= 21 ± 8° observed with an inclination
i
= 44
−6
10
° and PA = 150
−13
8
°. A high density of dust
n
= 5
−2.5
+5
M
⊙
pc
−3
is required to explain the contrast between the two edges by self-absorption from the closer one. The overall structure is itself obscured by a large foreground obscuration
A
V
∼ 75.
Conclusions.
The hot dust is not responsible for the obscuration of the central engine. The geometry and the orientation of the structure are different from those of the previously observed maser and molecular disks. We conclude that a single disk is unable to account for these differences, and favor a description of the source where multiple rings originating from different clouds are entangled around the central mass.
Context.
Several bright emission line regions have been observed in the central 100 parsecs of the active galaxy NGC 1068.
Aims.
We aim to determine the properties and ionization mechanism of three ...regions of NGC 1068: the nucleus (B) and two clouds located at 0.3″ and 0.7″ north of it (C and D).
Methods.
We combined SPHERE (0.95–1.65 μm) and SINFONI (1.5–2.45 μm) spectra for the three regions B, C, and D. We compared these spectra to several CLOUDY photoionization models and to the MAPPINGS III Library of Fast Radiative Shock Models.
Results.
The emission line spectra of the three regions are almost identical to each other and contribute to most of the emission line flux in the nuclear region. The emitting media contain multiple phases, the most luminous of which have temperatures ranging from 10
4.8
K to 10
6
K. Central photoionization models can reproduce some features of the spectra, but the fast radiative shock model provides the best fit to the data.
Conclusions.
The similarity between the three regions indicates that they belong to the same class of objects. Based on our comparisons, we conclude that they are shock regions located where the jet of the active galactic nucleus impacts massive molecular clouds.
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