sie_grad¶
-
simcado.source.sie_grad(x, y, par)[source]¶ Compute the deflection of an SIE (singular isothermal ellipsoid) potential
- Parameters
- x, ymeshgrid arrays
vectors or images of coordinates; should be matching numpy ndarrays
- parlist
vector of parameters with 1 to 5 elements, defined as follows: par[0]: lens strength, or ‘Einstein radius’ par[1]: (optional) x-center (default = 0.0) par[2]: (optional) y-center (default = 0.0) par[3]: (optional) axis ratio (default=1.0) par[4]: (optional) major axis Position Angle
in degrees c.c.w. of x axis. (default = 0.0)
- Returns
- xg, yggradients at the positions (x, y)
Notes
- This routine implements an ‘intermediate-axis’ convention.
- Analytic forms for the SIE potential can be found in:
Kassiola & Kovner 1993, ApJ, 417, 450 Kormann et al. 1994, A&A, 284, 285 Keeton & Kochanek 1998, ApJ, 495, 157
The parameter-order convention in this routine differs from that of a previous IDL routine of the same name by ASB.