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David Cole University of Leicester 9 December 2010.

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Presentation on theme: "David Cole University of Leicester 9 December 2010."— Presentation transcript:

1 David Cole University of Leicester 9 December 2010

2 Overview Background and motivation Results Basis for further work

3 Bars are common in disc galaxies Nair and Abraham 2010

4 How are bars formed Transfer of angular momentum Relative strength depends on the ability of the bar to grow Bar instability Massive halo suppresses bar instability (self gravity) but allows bar to grow. As bar increase in strength the pattern speed slows

5 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 mass In the Milky Way this would be 2 to 4 x 10 9 M

6 My work


8 No CMC Bar forms easily Can see transport of angular momentum from centre MD model forms very quickly due to the bar instability MH model forms more slowly due to suppression of self gravity – spheroid imposed on m=2 Fourier component of bar MH grows stronger – develops peanut As bar stengthens the pattern speed slows

9 Massive Disc


11 Massive Halo


13 Introduce CMC before bar formed


15 Add CMC when bar formed


17 Mechanisms Different mechanisms In 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

18 Orbits From Contopoulos & Payannopoulos (1980)

19 Conclusions Mechanisms for suppression of a bar different to destruction Just feasible BH can suppress a bar. Significant effect for MW mass disc at 8 x 10 8 M The timing and creation of bars/CMC have an effect on galaxy morphology Future – convergence tests changes in central softening Implications for gas transport

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