Nuclear Spirals in Galaxies

Maciejewski, Witold

doi:10.1007/978-0-387-72768-4_24

Cited by 2 publications

(1 citation statement)

References 18 publications

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“…To the contrary, hydrodynamical models by Maciejewski (2004b) showed that the nuclear spiral can propagate to the center of a galaxy as a shock in gas. Strong streaming motions (i.e., large velocity residuals), which take the form of kinematic spiral arms, are expected in the nuclear spiral shock (Maciejewski 2006). Kinematic spiral arms were already observed in emission from ionized gas in NGC 1097 (Fathi et al 2006), NGC 6951 (Storchi-Bergmann et al 2007), and M 83 (Fathi et al 2008).…”

Section: Introductionmentioning

confidence: 95%

Stellar and Molecular Gas Kinematics of NGC 1097: Inflow Driven by a Nuclear Spiral

Davies

Maciejewski

Hicks

et al. 2009

ApJ

124

126

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We present spatially resolved distributions and kinematics of the stars and molecular gas in the central 320 pc of NGC 1097. The stellar continuum confirms the previously reported three-arm spiral pattern extending into the central 100 pc. The stellar kinematics and the gas distribution imply this is a shadowing effect due to extinction by gas and dust in the molecular spiral arms. The molecular gas kinematics show a strong residual (i.e., non-circular) velocity, which is manifested as a two-arm kinematic spiral. Linear models indicate that this is the line-of-sight velocity pattern expected for a density wave in gas that generates a three-arm spiral morphology. We estimate the inflow rate along the arms. Using hydrodynamical models of nuclear spirals, we show that when deriving the accretion rate into the central region, outflow in the disk plane between the arms has to be taken into account. For NGC 1097, despite the inflow rate along the arms being ∼ 1.2 M yr −1 , the net gas accretion rate to the central few tens of parsecs is much smaller. The numerical models indicate that the inflow rate could be as little as ∼ 0.06 M yr −1 . This is sufficient to generate recurring starbursts, similar in scale to that observed, every 20-150 Myr. The nuclear spiral represents a mechanism that can feed gas into the central parsecs of the galaxy, with the gas flow sustainable for timescales of a gigayear.

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Section: Introductionmentioning

confidence: 95%

Stellar and Molecular Gas Kinematics of NGC 1097: Inflow Driven by a Nuclear Spiral

Davies

Maciejewski

Hicks

et al. 2009

ApJ

124

126

View full text Add to dashboard Cite

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The effect of stellar feedback on the formation and evolution of gas and dust tori in AGN

Schartmann

Meisenheimer

Klahr

et al. 2009

Monthly Notices of the Royal Astronomical Society

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Recently, the existence of geometrically thick dust structures in active galactic nuclei (AGN) has been directly proven with the help of interferometric methods in the mid‐infrared. The observations are consistent with a two‐component model made up of a geometrically thin and warm central disc, surrounded by a colder, fluffy torus component. Within the framework of an exploratory study, we investigate one possible physical mechanism, which could produce such a structure, namely the effect of stellar feedback from a young nuclear star cluster on the interstellar medium in centres of AGN. The model is realized by numerical simulations with the help of the hydrodynamics code tramp. We follow the evolution of the interstellar medium by taking discrete mass‐loss and energy ejection due to stellar processes, as well as optically thin radiative cooling into account. In a post‐processing step, we calculate observable quantities like spectral energy distributions (SEDs) and surface brightness distributions with the help of the radiative transfer code mc3d. The interplay between injection of mass, supernova explosions and radiative cooling leads to a two‐component structure made up of a cold geometrically thin, but optically thick and very turbulent disc residing in the vicinity of the angular momentum barrier, surrounded by a filamentary structure. The latter consists of cold long radial filaments flowing towards the disc and a hot tenuous medium in between, which shows both inwards and outwards directed motions. With the help of this modelling, we are able to reproduce the range of observed neutral hydrogen column densities of a sample of Seyfert galaxies as well as the relation between them and the strength of the silicate 10 μm spectral feature. Despite being quite crude, our mean Seyfert galaxy model is even able to describe the SEDs of two intermediate type Seyfert galaxies observed with the Spitzer Space Telescope.

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Nuclear Spirals in Galaxies

Cited by 2 publications

References 18 publications

Stellar and Molecular Gas Kinematics of NGC 1097: Inflow Driven by a Nuclear Spiral

Stellar and Molecular Gas Kinematics of NGC 1097: Inflow Driven by a Nuclear Spiral

The effect of stellar feedback on the formation and evolution of gas and dust tori in AGN

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