Tidal Stripping of Satellites

Class providing models of tidal stripping for satellites—the gravitational removal of dark matter and stellar mass from satellite halos as they orbit through the tidal field of their host halo. The tidal force strips material outside the tidal radius, reducing the satellite mass over time at a rate (in \(\mathrm{M}_\odot\) Gyr\(^{-1}\)) that depends on the satellite’s orbit, concentration, and the host potential. This mass loss sets the subhalo abundance, the galaxy-to-halo mass ratio in satellites, and drives the evolution of satellite galaxies toward quiescence.

Default implementation: satelliteTidalStrippingZentner2005

Methods

massLossRate → double precision

Returns the rate of tidal mass loss for node (in units of \(\mathrm{M}_\odot\)/Gyr).

  • type(treeNode) node [inout]

satelliteTidalStrippingDu2018

A satellite tidal stripping class which computes the rate at which a satellite loses mass from its FDM solitonic core, following Du et al. (2018). Tides excite the core out of its ground state, allowing it to lose mass by tunneling through the tidal barrier; the rate is set by the imaginary part of the energy eigenvalue of the perturbed core, for which equation (7) of Du et al. (2018) provides a fitting function in terms of the ratio of the central density of the core to the mean density of the host within the orbital radius.

Note that this class assumes that the satellite has been stripped down to its solitonic core, such that its bound mass is the total mass of the soliton. That total is taken to be four times the mass enclosed within the core radius, and it is therefore four times the rate of loss of the core mass which is returned here, as this class must report the rate of loss of the bound mass. The class is consequently not meaningful when applied to a satellite which retains an envelope around its core, and is intended for use only through nodeOperatorSatelliteTidalMassLossSoliton, which applies it only in that state.

satelliteTidalStrippingZentner2005

A satellite tidal stripping class which uses the formalism of Zentner et al. (2005) to compute the mass loss rate \(\dot{M}_\mathrm{sat}\):

\[\dot{M}_\mathrm{sat}=-\alpha \frac{M_\mathrm{sat}(>r_\mathrm{tidal})}{T_\mathrm{loss}},\]

where \(\alpha=\)[efficiency], \(T_\mathrm{loss}\) is the time scale of mass loss, and \(r_\mathrm{tidal}\) is the tidal radius of the satellite, given by the King (1962) formula:

\[r_\mathrm{tidal}=\left(\frac{GM_\mathrm{sat}}{\gamma_\mathrm{c}\omega^2-d^2\Phi/dr^2}\right)^{1/3},\]

where \(\omega\) is the orbital angular velocity of the satellite, \(\Phi(r)\) is the gravitational potential due to the host, and \(\gamma_\mathrm{c}\) is the efficiency of the centrifugal force when computing the tidal radius.

By default, \(T_\mathrm{loss}\) is taken to be the orbital time scale

\[T_\mathrm{orb} = {1 \over \hbox{max}(\omega/2\pi,v_\mathrm{r}/r)},\]

where \(\omega\) is the angular velocity of the satellite, \(v_\mathrm{r}\) is the radial velocity, \(r\) is the orbital radius. If [useDynamicalTimeScale] is set to true, \(T_\mathrm{loss}\) is taken to be the dynamical time scale computed at the tidal radius

\[T_\mathrm{dyn} = \sqrt{\frac{3 \pi}{16 G \overline{\rho}_\mathrm{sat}(r_\mathrm{tidal})}} = 2 \pi \sqrt{\frac{r_\mathrm{tidal}^3}{16 G M_\mathrm{sat}(r_\mathrm{tidal})}}.\]

(Default implementation)

Parameters

  • [efficiency] (real; default 2.5d0) — The dimensionless rate coefficient appearing in the Zentner et al. (2005) expression for the tidal mass loss rate from subhalos.

  • [useDynamicalTimeScale] (boolean; default .false.) — If true, the mass outside the tidal radius is assumed to be lost on dynamical time scale computed at the tidal radius. Otherwise, mass loss occurs on the orbital timescale of the satellite.

satelliteTidalStrippingZero

A satellite tidal stripping class in which the stripping rate is always zero.