David Cole University of Leicester 9 December 2010.

David ColeUniversity of Leicester

9 December 2010

OverviewBackground and motivationResultsBasis for further work

Nair and Abraham 2010

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

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

My work

My work

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

Introduce CMC before bar formed

Introduce CMC before bar formed

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

From Contopoulos & Payannopoulos (1980)

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