# galpy.df.evolveddiskdf.vmomentsurfacemass¶

evolveddiskdf.vmomentsurfacemass(R, n, m, t=0.0, nsigma=None, deg=False, epsrel=0.01, epsabs=1e-05, phi=0.0, grid=None, gridpoints=101, returnGrid=False, hierarchgrid=False, nlevels=2, print_progress=False, integrate_method='dopr54_c', deriv=None)[source]

NAME:

vmomentsurfacemass

PURPOSE:

calculate the an arbitrary moment of the velocity distribution at (R,phi) times the surfacmass

INPUT:

R - radius at which to calculate the moment (in natural units)

n - vR^n

m - vT^m

t= time at which to evaluate the DF (can be a list or ndarray; if this is the case, list needs to be in descending order and equally spaced)

nsigma - number of sigma to integrate the velocities over (based on an estimate, so be generous, but not too generous)

deg= azimuth is in degree (default=False)

epsrel, epsabs - scipy.integrate keywords (the integration calculates the ratio of this vmoment to that of the initial DF)

grid= if set to True, build a grid and use that to evaluate integrals; if set to a grid-objects (such as returned by this procedure), use this grid; if this was created for a list of times, moments are calculated for each time

gridpoints= number of points to use for the grid in 1D (default=101)

returnGrid= if True, return the grid object (default=False)

hierarchgrid= if True, use a hierarchical grid (default=False)

nlevels= number of hierarchical levels for the hierarchical grid

print_progress= if True, print progress updates

integrate_method= orbit.integrate method argument

deriv= None, ‘R’, or ‘phi’: calculates derivative of the moment wrt R or phi onnly with grid options

OUTPUT:

<vR^n vT^m x surface-mass> at R,phi (no support for units)

COMMENT:

grid-based calculation is the only one that is heavily tested (although the test suite also tests the direct calculation)

HISTORY:

2011-03-30 - Written - Bovy (NYU)