Detecting ionized bubbles in redshifted 21-cm maps |
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| Authors: | Kanan K Datta Somnath Bharadwaj T Roy Choudhury |
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| Institution: | E. Kharadze Georgian National Astrophysical Observatory, 2a Kazbegi Ave, Tbilisi 0160, Georgia |
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| Abstract: | Linear transient phenomena induced by flow non-normality in thin self-gravitating astrophysical discs are studied using the shearing sheet approximation. The considered system includes two modes of perturbations: vortex and (spiral density) wave. It is shown that self-gravity considerably alters the vortex mode dynamics; its transient (swing) growth may be several orders of magnitude stronger than in the non-self-gravitating case and two to three times larger than the transient growth of the wave mode. Based on this finding, we comment on the role of vortex mode perturbations in a gravitoturbulent state. We also describe the linear coupling of the perturbation modes, caused by the differential character of disc rotation. The coupling is asymmetric: vortex mode perturbations are able to excite wave mode perturbations, but not vice versa. This asymmetric coupling lends additional significance to the vortex mode as a participant in spiral density waves and shock manifestations in astrophysical discs. |
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| Keywords: | accretion accretion discs gravitation hydrodynamics instabilities planetary systems: protoplanetary discs |
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