david cole university of leicester 9 december 2010
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David ColeUniversity of Leicester
9 December 2010
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OverviewBackground and motivationResultsBasis for further work
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Nair and Abraham 2010
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How are bars formedTransfer of angular momentumRelative strength depends on the ability of the
bar to growBar instabilityMassive halo suppresses bar instability (self
gravity) but allows bar to grow.As bar increase in strength the pattern speed
slows
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Can a CMC destroy a bar?Shen & Sellwood (2004)Hozumi & Herquist( 2005)Athanassoula and Dehnen (2005)Bar can be destroyed but the CMC needs to be
unfeasibly massive ~ 5 to 10% of disk massIn the Milky Way this would be 2 to 4 x 109 M
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My work
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My work
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No CMCBar forms easilyCan see transport of angular momentum from
centreMD model forms very quickly due to the bar
instabilityMH model forms more slowly due to suppression
of self gravity – spheroid imposed on m=2 Fourier component of bar
MH grows stronger – develops peanutAs bar stengthens the pattern speed slows
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Introduce CMC before bar formed
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Introduce CMC before bar formed
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MechanismsDifferent mechanismsIn MD suppression by suppressing the swing
amplification – wave transmission through the centre
CMC blocks the transmission of the density wave through the centre
On introduction –destructing by suppression the box orbits which come arbitrarily close to the centre
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From Contopoulos & Payannopoulos (1980)
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ConclusionsMechanisms for suppression of a bar different to
destructionJust feasible BH can suppress a bar.Significant effect for MW mass disc at 8 x 108 M
The timing and creation of bars/CMC have an effect on galaxy morphology
Future – convergence testschanges in central softeningImplications for gas transport