mclindner/galcollide

Environment for creating initial conditions for galaxy collisions.

galcollide's Issues

Make units into parameters in Parameters.py for flexibility

Update documentation to include gas

Brentq fails when eccentricity is low

Problem: (-1*d_perigalactic * e) / (eccentricity - 1)) must be greater than initial separation for brentq to work

The _get_vxvy() function in Combine.py works fine for the parameters we are interested in, but if eccentricity is too low and (-1*d_perigalactic * e) / (eccentricity - 1)) - r) is negative,
brentq will fail. This makes sense given that f(a) and f(b) must have different signs, but I am unsure if this makes sense physics-wise. Obviously the initial separation must also be less than or equal to the intergalactic distance, and violating that errors as it should.

This may all be fine, but investigation is needed to make sure.

Error message:
Traceback (most recent call last):
File "Main.py", line 31, in
combined = two_bodys.combine()
File "/home/michael/NBody/Combine.py", line 205, in combine
x1, y1, vx1, vy1 = self._initial_conds(which_gal=self.Gal1)
File "/home/michael/NBody/Combine.py", line 157, in _initial_conds
x, y, vx, vy = self._get_vxvy(which_gal)
File "/home/michael/NBody/Combine.py", line 84, in _get_vxvy
self.inital_separation)
File "/home/michael/miniconda3/lib/python3.7/site-packages/scipy/optimize/zeros.py", line 776, in brentq
r = _zeros._brentq(f, a, b, xtol, rtol, maxiter, args, full_output, disp)
ValueError: f(a) and f(b) must have different signs

Period of oscillation in y versus time plot does not correspond to calculated period

The period given by T = np.sqrt(((4*np.pi ** 2) / (k ** 2)) * self.semimajor_axis ** 3) is used in the solve_ivp function, so the domain of the output should match the period. However, when I plot the output values, this is not the case. Both galaxies seem to orbit many more times than expected. To me this seems like a units problem, but I am having a hard time identifying the error.

Confirmation that orbits match physics needed

Validation that the orbits look as they should given the parameters that we input is needed - I will have to look through some textbooks. The units seem correct, but I am not 100% sure that changing the perigalactic distance is having the correct effect on the orbits.

Intergrate observation frame transformation into Combine.py

Now that the length/vel scaling isn't needed, we could the (fully combined) model into the observation frame at the last step of the code. Our movies would then be in the correct perspective.

Param file generation issue.

When there is no param file in the working directory, the NSteps in the param file created by running the code will be wrong. Running again fixes this when the file is overwritten. Maybe a default param file should be included, or specify in code.

Investigate order of mag difference between gas and no gas velocies in unscaled gas run

Fix the size of plots in wiki

Run a check with mass scaling factor = 1

We need to do this to ensure that the mass scaling isn't messing up the IC calculation math anywhere.