104 research outputs found
Nuclear spirals: gas in asymmetric galactic potential with a massive black hole
Nuclear spirals can provide a wealth of information about the nuclear
potential in disc galaxies. They form naturally as a gas response to
non-axisymmetry in the gravitational potential, even if the degree of this
asymmetry is very small. Linear wave theory well describes weak nuclear
spirals, but stronger asymmetries in the potential induce waves beyond the
linear regime, which appear as spiral shocks. If a central massive black hole
(MBH) is present, spiral shocks can extend all the way to its immediate
vicinity, and generate gas inflow up to 0.03 Msun/yr. This coincides with the
accretion rates needed to power local Active Galactic Nuclei.Comment: 4 pages, 3 figures, to appear in the proceedings of the IAU Symp.222
"The Interplay among Black Holes, Stars and ISM in Galactic Nuclei
Central mass accumulation in nuclear spirals
In central regions of non-axisymmetric galaxies high-resolution
hydrodynamical simulations indicate spiral shocks, which are capable of
transporting gas inwards. The efficiency of transport is lower at smaller
radii, therefore instead of all gas dropping onto the galactic centre, a
roughly uniform distribution of high-density gas develops in the gaseous
nuclear spiral downstream from the shock, and the shear in gas is very low
there. These are excellent conditions for star formation. This mechanism is
likely to contribute to the process of (pseudo-) bulge formation.Comment: 4 pages, 2 figures, to appear in the proceedings of the IAU Symposium
245, "Formation and Evolution of Galaxy Bulges
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