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;
}
/** @brief Main recipe, calculates the fraction of cold gas turned into stars due
* to star formation; the fraction of mass instantaneously recycled and
* returned to the cold gas; the fraction of gas reheated from cold to hot,
* ejected from hot to external and returned from ejected to hot due to
* SN feedback. */
void starformation(int p, int centralgal, double time, double dt, int nstep)
{
/*! Variables: reff-Rdisk, tdyn=Rdisk/Vmax, strdot=Mstar_dot, stars=strdot*dt*/
double tdyn, strdot=0., stars, cold_crit, metallicitySF;
if(Gal[p].Type == 0)
{
tdyn = Gal[p].GasDiskRadius / Gal[p].Vmax;
cold_crit = SfrColdCrit * Gal[p].Vmax/200. * Gal[p].GasDiskRadius*100.;
}
else
{
tdyn = Gal[p].GasDiskRadius / Gal[p].InfallVmax;
cold_crit = SfrColdCrit * Gal[p].InfallVmax/200. * Gal[p].GasDiskRadius*100.;
}
//standard star formation law (Croton2006, Delucia2007, Guo2010)
if(StarFormationModel == 0)
{
if(Gal[p].ColdGas > cold_crit)
strdot = SfrEfficiency * (Gal[p].ColdGas - cold_crit) / tdyn;
else
strdot = 0.0;
}
/*if(StarFormationModel == 1)
{
strdot = ALTERNATIVE STAR FORMATION LAW
}*/
/* Note that Units of dynamical time are Mpc/Km/s - no conversion on dt needed */
stars = strdot * dt;
if(stars < 0.0)
terminate("***error stars<0.0***\n");
//otherwise cold gas and stars share material in update_stars_due_to_reheat
#ifdef FEEDBACK_COUPLED_WITH_MASS_RETURN
if(stars > Gal[p].ColdGas)
stars = Gal[p].ColdGas;
#endif
mass_checks("recipe_starform #1",p);
mass_checks("recipe_starform #1.1",centralgal);
/* update for star formation
* updates Mcold, StellarMass, MetalsMcold and MetalsStellarMass
* in Guo2010 case updates the stellar spin -> hardwired, not an option */
/* Store the value of the metallicity of the cold phase when SF occurs */
if (Gal[p].ColdGas > 0.)
metallicitySF= metals_total(Gal[p].MetalsColdGas)/Gal[p].ColdGas;
else
metallicitySF=0.;
if (stars > 0.)
update_stars_due_to_reheat(p, centralgal, &stars);
mass_checks("recipe_starform #2",p);
mass_checks("recipe_starform #2.1",centralgal);
/* update the star formation rate */
/*Sfr=stars/(dt*steps)=strdot*dt/(dt*steps)=strdot/steps -> average over the STEPS*/
Gal[p].Sfr += stars / (dt * STEPS);
// update_from_star_formation can only be called
// after SD_feeedback recipe since stars need to be re_set once the reheated mass is known
// (star formation and feedback share the same fraction of cold gas)
if (stars > 0.)
update_from_star_formation(p, stars, false, nstep); // false indicates not a burst
update_massweightage(p, stars, time);
#ifndef FEEDBACK_COUPLED_WITH_MASS_RETURN
/* ifdef FEEDBACK_COUPLED_WITH_MASS_RETURN feedback is only called
* when stars die, inside DETAILED_METALS_AND_MASS_RETURN */
if (stars > 0.)
SN_feedback(p, centralgal, stars, "ColdGas");
#endif
#ifdef COMPUTE_SPECPHOT_PROPERTIES
#ifndef POST_PROCESS_MAGS
/* Update the luminosities due to the stars formed */
if (stars > 0.0)
add_to_luminosities(p, stars, time, dt, metallicitySF);
#endif //NDEF POST_PROCESS_MAGS
#endif //COMPUTE_SPECPHOT_PROPERTIES
if(Gal[p].DiskMass > 0.0)
check_disk_instability(p);
if (DiskRadiusModel== 0)
get_stellar_disk_radius(p);
}
