double collisional_starburst_recipe(double mass_ratio, int merger_centralgal, int centralgal,
double time, double deltaT, int nstep) //ROB: New variable 'nstep' added, for use in update_yields()
{
/** @brief If StarBurstRecipe = 1 (since Croton2006), the Somerville 2001
* model of bursts is used. The burst can happen for both major
* and minor mergers, with a fraction of the added cold gas from
* the satellite and central being consumed. SN Feedback from
* starformation is computed and the sizes of bulge and disk
* followed (not done for the other burst mode).*/
double mstars, reheated_mass, ejected_mass, fac, metallicitySF;
double CentralVvir, eburst, MergeCentralVvir, Ggas, EjectVmax, EjectVvir;
double SN_Energy, Reheat_Energy;
/* This is the major and minor merger starburst recipe of Somerville 2001.
* The coefficients in eburst are taken from TJ Cox's PhD thesis and should
* be more accurate then previous. */
Ggas=Gal[merger_centralgal].ColdGas;
/* the bursting fraction given the mass ratio */
/* m_dot = 0.56*(m_sat/m_central)^0.7*m_gas */
eburst = SfrBurstEfficiency * pow(mass_ratio, SfrBurstSlope);
//eburst = 0.56 * pow(mass_ratio, 0.7);
mstars = eburst * Gal[merger_centralgal].ColdGas;
if(mstars < 0.0)
mstars = 0.0;
/* this bursting results in SN feedback on the cold/hot gas
* TODO this is the same code used in star_formation_and_feedback.c
* and should be merged if possible. */
if(FeedbackRecipe == 0 || FeedbackRecipe == 1) {
if (Gal[merger_centralgal].Type == 0)
reheated_mass = FeedbackReheatingEpsilon *
mstars*(.5+1./pow(Gal[merger_centralgal].Vmax/ReheatPreVelocity,ReheatSlope));
else
reheated_mass = FeedbackReheatingEpsilon *
mstars*(.5+1./pow(Gal[merger_centralgal].InfallVmax/ReheatPreVelocity,ReheatSlope));
}
//Make sure that the energy used does not exceed the SN energy (central subhalo Vvir used)
if(FeedbackRecipe == 0 || FeedbackRecipe == 1) {
if (reheated_mass * Gal[merger_centralgal].Vvir * Gal[merger_centralgal].Vvir > mstars * EtaSNcode * EnergySNcode)
reheated_mass = mstars * EtaSNcode * EnergySNcode / Gal[merger_centralgal].Vvir / Gal[merger_centralgal].Vvir;
}
/* cant use more cold gas than is available! so balance SF and feedback */
if((mstars + reheated_mass) > Gal[merger_centralgal].ColdGas) {
fac = Gal[merger_centralgal].ColdGas / (mstars + reheated_mass);
mstars *= fac;
reheated_mass *= fac;
}
if (merger_centralgal == centralgal)
{
EjectVmax=Gal[centralgal].Vmax;
EjectVvir=Gal[centralgal].Vvir;// main halo Vvir
}
else
{
EjectVmax=Gal[merger_centralgal].InfallVmax;
EjectVvir=Gal[merger_centralgal].Vvir; //central subhalo Vvir
}
/* determine ejection*/
if(FeedbackRecipe == 0) {
ejected_mass = (FeedbackEjectionEfficiency* (EtaSNcode * EnergySNcode) *mstars
* min(1./FeedbackEjectionEfficiency,.5+1/pow(EjectVmax/EjectPreVelocity,EjectSlope))
- reheated_mass*EjectVvir*EjectVvir) /(EjectVvir*EjectVvir);
}
else if(FeedbackRecipe == 1)
{
SN_Energy = .5 * mstars * (EtaSNcode * EnergySNcode);
Reheat_Energy = .5 * reheated_mass * EjectVvir * EjectVvir;
ejected_mass = (SN_Energy - Reheat_Energy)/(0.5 * FeedbackEjectionEfficiency*(EtaSNcode * EnergySNcode));
if(FeedbackEjectionEfficiency*(EtaSNcode * EnergySNcode)<EjectVvir*EjectVvir)
ejected_mass =0.0;
}
// Finished calculating mass exchanges, so just check that none are negative
if (reheated_mass < 0.0) reheated_mass = 0.0;
if (ejected_mass < 0.0) ejected_mass = 0.0;
/* update the star formation rate */
#ifdef SAVE_MEMORY
Gal[merger_centralgal].Sfr += mstars / deltaT;
#else
for(outputbin = 0; outputbin < NOUT; outputbin++) {
if(Halo[halonr].SnapNum == ListOutputSnaps[outputbin]) {
Gal[merger_centralgal].Sfr[outputbin] += mstars / deltaT;
break;
}
}
#endif
/* Store the value of the metallicity of the cold phase when SF occurs.
* Used to update luminosities below */
#ifdef METALS
//metallicitySF = Gal[merger_centralgal].MetalsColdGas.type2/Gal[merger_centralgal].ColdGas;
metallicitySF = metals_total(Gal[merger_centralgal].MetalsColdGas)/Gal[merger_centralgal].ColdGas;
#else
metallicitySF = Gal[merger_centralgal].MetalsColdGas/Gal[merger_centralgal].ColdGas;
#endif
mass_checks("collisional_starburst_recipe #1",merger_centralgal);
if (mstars > 0.)
update_from_star_formation(merger_centralgal, mstars, deltaT/STEPS, nstep);
mass_checks("collisional_starburst_recipe #2",merger_centralgal);
// Do not call if Gal[merger_centralgal].ColdGas < 1e-8?
if (reheated_mass + ejected_mass > 0.)
update_from_feedback(merger_centralgal, centralgal, reheated_mass, ejected_mass);
#ifndef POST_PROCESS_MAGS
/* update the luminosities due to the stars formed */
if (mstars > 0.0)
add_to_luminosities(merger_centralgal, mstars, time, metallicitySF);
#endif
if (Ggas > 0.)
return mstars/Ggas;
else
return 0.0;
}
/* there are two modes for supernova feedback corresponding to when the mass returning
* by dying stars is returned to the cold gas - reheat and ejection; and when the mass
* is returned to the hot gas - onle ejection.*/
void SN_feedback(int p, int centralgal, double stars, char feedback_location[])
{
double CentralVvir, MergeCentralVvir=0., EjectVmax, EjectVvir, SN_Energy, Reheat_Energy, fac;
double reheated_mass=0., ejected_mass=0.;
/* SN FEEDBACK MODEL */
/* In Guo2010 type 1s can eject, reincorporate gas and get gas from their
* own satellites (is not sent to the type 0 galaxy as in Delucia2007),
* for gas flow computations:
* If satellite is inside Rvir of main halo, Vvir of main halo used
* If it is outside, the Vvir of its central subhalo is used. */
if (strcmp(feedback_location,"HotGas")==0)
reheated_mass = 0.;
else
if (strcmp(feedback_location,"ColdGas")==0)
{
CentralVvir = Gal[centralgal].Vvir; // main halo Vvir
MergeCentralVvir = Gal[Gal[p].CentralGal].Vvir; //central subhalo Vvir
mass_checks("recipe_starform #0",p);
mass_checks("recipe_starform #0.1",centralgal);
// Feedback depends on the circular velocity of the host halo
// Guo2010 - eq 18 & 19
if(FeedbackReheatingModel == 0)
{
if (Gal[Gal[p].CentralGal].Type == 0)
reheated_mass = FeedbackReheatingEpsilon * stars *
(.5+1./pow(Gal[Gal[p].CentralGal].Vmax/ReheatPreVelocity,ReheatSlope));
else
reheated_mass = FeedbackReheatingEpsilon * stars *
(.5+1./pow(Gal[Gal[p].CentralGal].InfallVmax/ReheatPreVelocity,ReheatSlope));
if (reheated_mass * Gal[Gal[p].CentralGal].Vvir * Gal[Gal[p].CentralGal].Vvir > stars * (EtaSNcode * EnergySNcode))
reheated_mass = stars * (EtaSNcode * EnergySNcode) / (Gal[Gal[p].CentralGal].Vvir * Gal[Gal[p].CentralGal].Vvir);
}
/*else if(FeedbackReheatingModel == 1)
{
reheated_mass = ALTERNATIVE Reheating LAW ;
}*/
if(reheated_mass > Gal[p].ColdGas)
reheated_mass = Gal[p].ColdGas;
}// end if feedback_location
/* Determine ejection (for FeedbackEjectionModel 2 we have the dependence on Vmax)
* Guo2010 - eq 22
* Note that satellites can now retain gas and have their own gas cycle*/
if (Gal[Gal[p].CentralGal].Type == 0)
{
EjectVmax=Gal[centralgal].Vmax;
EjectVvir=Gal[centralgal].Vvir;// main halo Vvir
}
else
{
EjectVmax=Gal[Gal[p].CentralGal].InfallVmax;
EjectVvir=Gal[Gal[p].CentralGal].Vvir; //central subhalo Vvir
}
if(FeedbackEjectionModel == 0)
{
ejected_mass = (FeedbackEjectionEfficiency* (EtaSNcode * EnergySNcode) * stars *
min(1./FeedbackEjectionEfficiency, .5+1/pow(EjectVmax/EjectPreVelocity,EjectSlope)) -
reheated_mass*EjectVvir*EjectVvir) /(EjectVvir*EjectVvir);
}
else if(FeedbackEjectionModel == 1)//the ejected material is assumed to have V_SN
{
SN_Energy = .5 * stars * (EtaSNcode * EnergySNcode);
Reheat_Energy = .5 * reheated_mass * EjectVvir * EjectVvir;
ejected_mass = (SN_Energy - Reheat_Energy)/(0.5 * FeedbackEjectionEfficiency*(EtaSNcode * EnergySNcode));
//if VSN^2<Vvir^2 nothing is ejected
if(FeedbackEjectionEfficiency*(EtaSNcode * EnergySNcode)<EjectVvir*EjectVvir)
ejected_mass =0.0;
}
// Finished calculating mass exchanges, so just check that none are negative
if (reheated_mass < 0.0) reheated_mass = 0.0;
if (ejected_mass < 0.0) ejected_mass = 0.0;
/* Update For Feedback */
/* update cold, hot, ejected gas fractions and respective metallicities
* there are a number of changes introduced by Guo2010 concerning where
* the gas ends up */
//ejected_mass = 0.01*Gal[centralgal].HotGas;
if (reheated_mass + ejected_mass > 0.)
update_from_feedback(p, centralgal, reheated_mass, ejected_mass);
}
