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Chemistry in Gear
*****************
Setting the mass range
""""""""""""""""""""""
in chimie.txt
For each stellar particle, we first find the min and max live time of a particle::
/* minimum live time for a given metallicity */
minlivetime = star_lifetime(StP[m].Metal[NELEMENTS-1],Cp->Mmax*SOLAR_MASS/All.UnitMass_in_g)*All.HubbleParam;
/* maximum live time for a given metallicity */
maxlivetime = star_lifetime(StP[m].Metal[NELEMENTS-1],Cp->Mmin*SOLAR_MASS/All.UnitMass_in_g)*All.HubbleParam;
where the function :c:func:`star_lifetime` has been used.
Then, we compute ``t01`` and ``t02``, which bracket the time interval between the current age and
the time during which the stellar particule was created.
Then, ``m1`` and ``m2`` are determined, corresponding to the mass of stars that end their life
during the current time step.
``m1`` is either::
m1 = star_mass_from_age(StP[m].Metal[NELEMENTS-1],t02/All.HubbleParam)*All.HubbleParam;
or::
m1 = Cp->Mmin*SOLAR_MASS/All.UnitMass_in_g*All.HubbleParam;
Similarly, ``m2`` is either::
m2 = star_mass_from_age(StP[m].Metal[NELEMENTS-1],t01/All.HubbleParam)*All.HubbleParam;
or::
m2 = Cp->Mmax*SOLAR_MASS/All.UnitMass_in_g*All.HubbleParam;
where we have used :c:func:`star_mass_from_age`.
Computing the number of dying stars
"""""""""""""""""""""""""""""""""""
Once we know that some stars may die during the
current timestep, we need to compute the number of dying stars
The number(float) of SNIa is given by (:c:func:`SNIa_rate`)::
NSNIa = SNIa_rate(m1/All.HubbleParam,m2/All.HubbleParam)*M0/All.HubbleParam;
The number(float) of SNII is given by (:c:func:`SNII_rate`)::
NSNII = SNII_rate(m1/All.HubbleParam,m2/All.HubbleParam)*M0/All.HubbleParam;
In the case where we use the flag ``CHIMIE_MC_SUPERNOVAE``,
``NSNIa`` and ``NSNII`` are rounded to integer values, according to
some probabilities::
double fNSNIa,fNSNII;
fNSNIa = NSNIa-floor(NSNIa);
NSNIa = floor(NSNIa);
if (get_Chimie_random_number(P[i].ID) < fNSNIa)
NSNIa = NSNIa+1;
fNSNII = NSNII-floor(NSNII);
NSNII = floor(NSNII);
if (get_Chimie_random_number(P[i].ID) < fNSNII)
NSNII = NSNII+1;
Computing ejected mass and yields
"""""""""""""""""""""""""""""""""
If ``CHIMIE_MC_SUPERNOVAE`` is used, the total mass, as well as the ejected mass of each element
is computed using the function :c:func:`Total_single_mass_ejection`::
Total_single_mass_ejection(0.5*(m1+m2)/All.HubbleParam,metals,NSNII,NSNIa,0);
This functions fill the array ``SingleEjectedMass``.
This array is then copied to the variables
containing the total gas mass and the mass ejected per element::
StP[m].TotalEjectedGasMass = SingleEjectedMass[0]*All.HubbleParam;
for (k=0;k<NELEMENTS;k++)
StP[m].TotalEjectedEltMass[k] = SingleEjectedMass[k+2]*All.HubbleParam;
If ``CHIMIE_MC_SUPERNOVAE`` is not used, the ejected total mass, as well as the ejected mass of each element
is computed using the function :c:func:`Total_mass_ejection`::
Total_mass_ejection(m1/All.HubbleParam,m2/All.HubbleParam,M0/All.HubbleParam,metals);
This functions fill the array ``EjectedMass``.
This array is then copied to the variables
containing the total gas mass and the mass ejected per element::
StP[m].TotalEjectedGasMass = EjectedMass[0]*All.HubbleParam;
for (k=0;k<NELEMENTS;k++)
StP[m].TotalEjectedEltMass[k] = EjectedMass[k+2]*All.HubbleParam;
Computing ejected energy
""""""""""""""""""""""""
Finally, the total ejected energy per mass unit is obtained by multiplying the number of SNIa and SNII
by the assumed supernova energy::
StP[m].TotalEjectedEgySpec = All.ChimieSupernovaEnergy* (NSNIa + NSNII) /StP[m].TotalEjectedGasMass;
Variables used for the ejection of mass and energy
""""""""""""""""""""""""""""""""""""""""""""""""""
The variables used for the ejection of mass and energy are::
StP[m].TotalEjectedGasMass
StP[m].TotalEjectedEltMass[k]
StP[m].TotalEjectedEgySpec
StP[m].NumberOfSNIa
StP[m].NumberOfSNII
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