| 1. |
- Fathi, Kambiz, et al.
(author)
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Two-Dimensional Kinematics of a Bar and Central Disk in NGC5448
- 2007
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Conference paper (other academic/artistic)abstract
- We analyse SAURON kinematic maps of the inner kpc of the early-type (Sa) barred spiral galaxy NGC 5448. The observed morphology and kinematics of the emission-line gas is patchy and perturbed, indicating clear departures from circular motion. The kinematics of the stars is more regular, and displays a small inner disk-like system embedded in a large-scale rotating structure. We focus on the [O iii] gas, and use a harmonic decomposition formalism to analyse the gas velocity field. The higher-order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model, which is derived using linear theory. Our study illustrates how the harmonic decomposition formalism can be used as a powerful tool to quantify non-circular motions in observed gas velocity fields.
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| 2. |
- Aros, Francisco I, et al.
(author)
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Dynamical modelling of globular clusters: challenges for the robust determination of IMBH candidates
- 2020
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 499:4, s. 4646-4665
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Journal article (peer-reviewed)abstract
- The presence or absence of intermediate-mass black holes (IMBHs) at the centre of Milky Way globular clusters (GCs) is still an open question. This is due to either observational restrictions or limitations in the dynamical modelling method; in this work, we explore the latter. Using a sample of high-end Monte Carlo simulations of GCs, with and without a central IMBH, we study the limitations of spherically symmetric Jeans models assuming constant velocity anisotropy and mass-to-light ratio. This dynamical method is one of the most widely used modelling approaches to identify a central IMBH in observations.With these models, we are able to robustly identify and recover the mass of the central IMBH in our simulation with a high-mass IMBH (MIMBH/MGC∼4 per cent). Simultaneously, we show that it is challenging to confirm the existence of a low-mass IMBH (MIMBH/MGC∼0.3 per cent), as both solutions with and without an IMBH are possible within our adopted error bars. For simulations without an IMBH, we do not find any certain false detection of an IMBH. However, we obtain upper limits that still allow for the presence of a central IMBH. We conclude that while our modelling approach is reliable for the high-mass IMBH and does not seem to lead towards a false detection of a central IMBH, it lacks the sensitivity to robustly identify a low-mass IMBH and to definitely rule out the presence of an IMBH when it is not there.
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| 3. |
- Aros, Francisco I, et al.
(author)
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Using binaries in Globular Clusters to catch sight of Intermediate-Mass Black Holes
- 2021
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 508:3, s. 4385-4398
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Journal article (peer-reviewed)abstract
- The dynamical evolution of globular clusters (GCs) is tied to their binary population, as binaries segregate to the cluster centre, leading to an increased binary fraction in the core. This central overabundance of mainly hard binaries can serve as a source of energy for the cluster and has a significant effect on the observed kinematics, such as artificially increasing the observed line-of-sight velocity dispersion. We analyse the binary fractions and distributions of 95 simulated GCs, with and without an intermediate-mass black hole (IMBH) in their centre. We show that an IMBH will not only halt the segregation of binaries towards the cluster centre, but also, directly and indirectly, disrupt the binaries that segregate, thus, depleting binaries in the cluster core. We illustrate this by showing that clusters with an IMBH have fewer binaries and flatter radial binary distributions than their counterparts without one. These differences in the binary fraction and distribution provide an additional indicator for the presence of a central IMBH in GCs. In addition, we analyse the effects of the binary fraction on the line-of-sight velocity dispersion in the simulated GCs and find that binaries can cause an overestimation of up to 70percent of the velocity dispersion within the core radius. Using recent VLT/MUSE observations of NGC 3201 by Giesers et al. (2019), we find an overestimation of 32.2±7.8percent in the velocity dispersion that is consistent with the simulations and illustrates the importance of accurately accounting for the binary population when performing kinematic or dynamical analysis.
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| 4. |
- Fathi, Kambiz, et al.
(author)
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ALMA FOLLOWS STREAMING OF DENSE GAS DOWN TO 40 PC FROM THE SUPERMASSIVE BLACKHOLE IN NGC 1097
- 2013
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In: Astrophysical Journal Letters. - 2041-8205. ; 770:2, s. L27-
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Journal article (peer-reviewed)abstract
- We present a kinematic analysis of the dense gas in the central 200 parsecs of thenearby galaxy NGC1097, based on Cycle 0 observations with the Atacama LargeMillimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line to trace the densest interstellar molecular gas (nH2 ~ 10^8 cm-3), and quantify its kinematics by means of Fourier decomposition. We find a striking similarity between the ALMA kinematic data and the analytic spiral in ow model that we have previously constructed based onionized gas velocity fields on larger scales. We are able to follow dense gas streamingdown to 40 pc distance from the supermassive black hole in this Seyfert 1 galaxy. In order to fulll marginal stability, we deduce that the dense gas is conned to a very thin disc, with 6.0+2.2-2.7 10^6 Msun dynamical mass inside a radius of 40 pc. Finally, we derive a dense gas in ow rate of 0.09Msun yr-1 at 40 pc radius. Combined with previous valuesfrom the H and CO gas, we calculate a combined molecular and ionized gas in ow rateof 0.2Msun yr-1 at 40 pc distance from the central supermassive black hole of NGC1097.
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| 5. |
- Piñol-Ferrer, Nuria, 1984-, et al.
(author)
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Bar pattern speed and position of the circumnuclear ringin NGC 1097
- 2014
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 438:2, s. 971-982
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Journal article (peer-reviewed)abstract
- We present the first galactic-scale model of the gas dynamics of the prototype barred Seyfert 1 galaxy NGC 1097. We use large scale FaNTOmM Fabry-Perot interfer-ometric data covering the entire galactic disc and combined the distribution andkinematics maps with high resolution two-dimensional spectroscopy from the Gemini telescope. We build a dynamical model for the gravitational potential by applying the analytic solution to the equations of motion, with in the epicyclic approximation. Our model reproduces all the significant kinematic and structural signatures of thisgalaxy. We find that the primary bar is 7.9±0.6 kpc long and has a pattern speedof 36 ± 2 km s−1 kpc−1. This places the corotation radius at 8.6±0.5 kpc, the outer Lindblad resonance at 14.9±0.9 kpc and two inner Lindblad resonances at 60±5 pcand 2.9±0.1 kpc. These derivations lead to a ratio of the corotation radius over barlength of 1.0–1.2, which is in concordance with simulations of barred galaxies. Our model presents evidence that the circumnuclear ring in this galaxy is not located near any of the resonance radii in this galaxy. The ring might have once formed at the outer inner Lindblad resonance radius, and it has been migrating inward, toward the centre of the galactic gravitational potential.
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| 6. |
- Thater, Sabine, et al.
(author)
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Cross-checking SMBH mass estimates in NGC 6958-I. Stellar dynamics from adaptive optics-assisted MUSE observations
- 2022
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 509:4, s. 5416-5436
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Journal article (peer-reviewed)abstract
- Supermassive black hole masses (M (BH)) can dynamically be estimated with various methods and using different kinematic tracers. Different methods have only been cross-checked for a small number of galaxies and often show discrepancies. To understand these discrepancies, detailed cross-comparisons of additional galaxies are needed. We present the first part of our cross-comparison between stellar- and gas-based M-BH estimates in the nearby fast-rotating early-type galaxy NGC 6958. The measurements presented here are based on ground-layer adaptive optics-assisted Multi-Unit Spectroscopic Explorer (MUSE) science verification data at around 0."6 spatial resolution. The spatial resolution is a key ingredient for the measurement and we provide a Gaussian parametrization of the adaptive optics-assisted point spread function for various wavelengths. From the MUSE data, we extracted the stellar kinematics and constructed dynamical models. Using an axisymmetric Schwarzschild technique, we measured an M-BH of (3.6(-2.4)(+2.7)) x10(8) M-circle dot at 3 sigma significance taking kinematical and dynamical systematics (e.g. radially varying mass-to-light ratio) into account. We also added a dark halo, but our data do not allow us to constrain the dark matter fraction. Adding dark matter with an abundance matching prior results in a 25 per cent more massive black hole. Jeans anisotropic models return M-BH of (4.6(-2.7)(+2.5)) x10(8) and (8.6(-0.8)(+0.8)) x10(8) M-circle dot at 3 sigma confidence for spherical and cylindrical alignments of the velocity ellipsoid, respectively. In a follow-up study, we will compare the stellar-based M (BH) with those from cold and warm gas tracers, which will provide additional constraints for the M-BH for NGC 6958, and insights into assumptions that lead to potential systematic uncertainty.
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| 7. |
- van de Ven, Glenn, et al.
(author)
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Kinematic Analysis of Nuclear Spirals : Feeding the Black Hole in NGC 1097
- 2010
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In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 723:1, s. 767-780
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Journal article (peer-reviewed)abstract
- We present a harmonic expansion of the observed line-of-sight velocity field as a method to recover and investigate spiral structures in the nuclear regions of galaxies. We apply it to the emission-line velocity field within the circumnuclear star-forming ring of NGC 1097, obtained with the GMOS-IFU spectrograph. The radial variation of the third harmonic terms is well described by a logarithmic spiral, from which we interpret that the gravitational potential is weakly perturbed by a two-arm spiral density wave with an inferred pitch angle of 52° ± 4°. This interpretation predicts a two-arm spiral distortion in the surface brightness, as hinted by the dust structures in central images of NGC 1097, and predicts a combined one-arm and three-arm spiral structure in the velocity field, as revealed in the non-circular motions of the ionized gas. Next, we use a simple spiral perturbation model to constrain the fraction of the measured non-circular motions that is due to radial inflow. We combine the resulting inflow velocity with the gas density in the spiral arms, inferred from emission-line ratios, to estimate the mass inflow rate as a function of radius, which reaches about 0.011 M ☉ yr–1 at a distance of 70 pc from the center. This value corresponds to a fraction of about 4.2 × 10–3 of the Eddington mass accretion rate onto the central black hole in this LINER/Seyfert1 galaxy. We conclude that the line-of-sight velocity can not only provide a cleaner view of nuclear spirals than the associated dust, but that the presented method also allows the quantitative study of these possibly important links in fueling the centers of galaxies, including providing a constraint on the mass inflow rate as a function of radius.
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