galpy.df.evolveddiskdf.sigmaRT¶

evolveddiskdf.sigmaRT(R, t=0.0, nsigma=None, deg=False, epsrel=0.01, epsabs=1e-05, phi=0.0, grid=None, gridpoints=101, returnGrid=False, surfacemass=None, meanvR=None, meanvT=None, hierarchgrid=False, nlevels=2, integrate_method='dopr54_c')[source]

Calculate the radial-rotational co-variance of the velocity distribution at (R,phi)

Parameters:
• R (float) – Radius at which to calculate the moment (can be Quantity)

• phi (float, optional) – Azimuth (rad unless deg=True; can be Quantity), by default 0.0

• t (float or array, optional) – 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) (can be Quantity), by default 0.0

• surfacemass (float, optional) – If set use this pre-calculated surfacemass and mean rotational velocity, by default None

• meanvT (float, optional) – If set use this pre-calculated surfacemass and mean rotational velocity, by default None

• nsigma (float, optional) – Number of sigma to integrate the velocities over (based on an estimate, so be generous), by default None

• deg (bool, optional) – Azimuth is in degree (default=False); do not set this when giving phi as a Quantity, by default False

• epsrel (float, optional) – Scipy.integrate keywords (the integration calculates the ratio of this vmoment to that of the initial DF), by default 1.0e-02

• epsabs (float, optional) – Scipy.integrate keywords (the integration calculates the ratio of this vmoment to that of the initial DF), by default 1.0e-05

• grid (bool or evolveddiskdfGrid or evolveddiskdfHierarchicalGrid, optional) – 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, by default None

• gridpoints (int, optional) – Number of points to use for the grid in 1D (default=101), by default 101

• returnGrid (bool, optional) – If True, return the grid object (default=False), by default False

• hierarchgrid (bool, optional) – If True, use a hierarchical grid (default=False), by default False

• nlevels (int, optional) – Number of hierarchical levels for the hierarchical grid, by default 2

• integrate_method (str, optional) – orbit.integrate method argument, by default “dopr54_c”

Returns:

Covariance of vR and vT or tuple of covariance of vR and vT and grid object

Return type:

float or tuple

Notes

• 2011-03-31 - Written - Bovy (NYU)