Recent content by florian101

hello I would like to know the frequency width of a decaying axion Lets say the axion has a mass of 10^-6 eV and it decays via the primakoff effect within a B field into one photon. Because there is only one photon in the final state I would assume that the photon frequency is quite narrow but...

Thanks Wallace... Yes it makes sense that I should not trust the simulation for smaller scales then the softening length... Just for completeness I use dark matter particles with different mass and therefore different softening length... The name Star, Bulge, disk... what you find in the...

thanks for the answers... I will try to provide some more details of what I am trying to do... First of all it is true that if you start with a distribution of matter and let gravity work you will end up with a universe full of DM halos. I am not interested in DM evolution... I just assume I...

Hello I try to get stable dark matter halos with n-body simulations. I set up the halo following a NFW-profile and I define the velocity distribution with a Gauss distribution or Edington inversion (the result is the same). After approximately 2Gyr my cusp turns into a core...?? I use about...

Hay Can anybody tell me how to change from km/s to kpc/Gyr? I found a facto of 0.96 but I need it very precise and I am not sure about the exact definition of a Gyr because people use different definitions... kpc/Gyr = 3.08568e16km/3.2e16s = 0.964275? thanks a lot for help regards florian

hay ok if anybody is interested I think I found the solution... d phi = - GdM/r Therefore r<r': phi_1 = -GM(r')/r' r>r': phi_2 = int^infinity_r' rho(R)*R dR phi = phi_1 + phi_2 The result shows a small discrepancy which I do not understand so far but I think this is a numerical...

ok I had a chat to my prof and he told me that the potential should go with ln(r) so the equation we are using is wrong...:-( florian

I did the simulation by myself. The halo mass within the viral radius (r_viral = 32.4kpc) is 2e09 solar masses. The scale radius is 0.81kpc and the concentration parameter is 40. Just to be sure about the formula E = 1/2*m*v^2 - grav_const*m*M(r_viral)/r r is still the position of the...

I thought because the force within r (position of the particle) is not zero and outside r it is zero I have two different contributions to the potential. Outside it should be constant because the gradient of the potential (=force) has to be zero and within r it should depend on r... If I use...

In principle I would like to see a lindblad plot of all dark matter particles in my dark matter halo. This means a plot with total energy vs. angular momentum. To calculate the total energy I need the potential to calculate the potential energy. My question is therefore whether E = 1/2*m*v^2 -...

Hay I would like to calculate the potential energy of a particle which is within a big dark matter halo. The Newton shell theorem says that if I have a particle within a spherical mass distribution (let us say at radius r) the mass with R>r exert no net Force to the particle. But there is a...