def Jz(self,**kwargs):
        """
        NAME:
           Jz
        PURPOSE:
           Calculate the vertical action
        INPUT:
           fixed_quad= (False) if True, use n=10 fixed_quad
           +scipy.integrate.quad keywords
        OUTPUT:
           J_z(R,vT,vT)/ro/vc + estimate of the error
        HISTORY:
           2012-11-27 - Written - Bovy (IAS)
        """
        if hasattr(self,'_JZ'): #pragma: no cover
            return self._JZ
        vmin= self.calcVmin()
        if (nu.pi/2.-vmin) < 10.**-7: return nu.array([0.])
        order= kwargs.pop('order',10)
        if kwargs.pop('fixed_quad',False):
            # factor in next line bc integrand=/2delta^2
            self._JZ= 2./nu.pi*nu.sqrt(2.)*self._delta \
                *integrate.fixed_quad(_JzStaeckelIntegrand,
                                      vmin,nu.pi/2,
                                      args=(self._E,self._Lz,self._I3V,
                                            self._delta,
                                            self._ux,self._coshux**2.,
                                            self._sinhux**2.,
                                            self._potupi2,self._pot),
                                      n=order,
                                      **kwargs)[0]
        else:
            # factor in next line bc integrand=/2delta^2
            self._JZ= 2./nu.pi*nu.sqrt(2.)*self._delta \
                *integrate.quad(_JzStaeckelIntegrand,
                                vmin,nu.pi/2,
                                args=(self._E,self._Lz,self._I3V,
                                      self._delta,
                                      self._ux,self._coshux**2.,
                                      self._sinhux**2.,
                                      self._potupi2,self._pot),
                                **kwargs)[0]
        return self._JZ
NAME:
           Jz
        PURPOSE:
           Calculate the vertical action
        INPUT:
           fixed_quad= (False) if True, use n=10 fixed_quad
           +scipy.integrate.quad keywords
        OUTPUT:
           J_z(R,vT,vT)/ro/vc + estimate of the error
        HISTORY:
           2012-11-27 - Written - Bovy (IAS)