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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 starforming ring of NGC1097, obtained with the GMOS-IFU spectrograph. The radial variation of the third harmonic terms are 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 inferred pitch angle of of 52+/-4 degrees. This interpretation predicts a two-arm spiral distortion in the surface brightness, as hinted by the dust structures in central images of NGC1097, and predicts a combined one-arm and three-arm spiral structure in the velocity field, as revealed in the non-circular motions of the ionised gas within the circumnuclear region of this galaxy. 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 Msun/yr at a distance of 70 pc from the center. This value corresponds to a fraction of about 4.2 x 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 not only can 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 handle on the mass inflow rate as a function of radius.
We report ALMA observations of CO(3-2) emission in the Seyfert2/starburst galaxy NGC1808, at a spatial resolution of 4pc. Our aim is to investigate the morphology and dynamics of the gas inside the central 0.5kpc, and to probe nuclear feeding and fee
Warm absorbers are found in many AGN and consist of clouds moving at moderate radial velocities, showing complex ionization structures and having moderate to large column densities. Using 1D numerical calculations, we confirm earlier suggestions that
We introduce massive black holes (BHs) in the Feedback In Realistic Environments project and perform high-resolution cosmological hydrodynamic simulations of quasar-mass halos ($M_{rm halo}(z=2) approx 10^{12.5},rm{M}_{odot}$) down to $z=1$. These si
We use hydrodynamical simulations to construct a new coherent picture for the gas flow in the Central Molecular Zone (CMZ), the region of our Galaxy within $Rleq 500, mathrm{pc}$. We relate connected structures observed in $(l,b,v)$ data cubes of mol
The inter-line comparison between high- and low-ionization emission lines has yielded a wealth of information on the quasar broad line region (BLR) structure and dynamics, including perhaps the earliest unambiguous evidence in favor of a disk + wind