More Detailed Models: The GalaxyPopulation object¶
Most of the global 21-cm examples in the documentation tie the volume-averaged emissivity of galaxies to the rate at which mass collapses into dark matter halos. Because of this, they are referred to as \(f_{\mathrm{coll}}\) models throughout, and are selected by setting pop_model='fcoll'. In the code, they are represented by GalaxyAggregate objects.
However, we can also run more detailed models in which the properties of galaxies are allowed to change as a function of halo mass, redshift, and/or potentially other quantities.
A few usual imports before we begin:
import ares
import numpy as np
import matplotlib.pyplot as pl
A Simple GalaxyPopulation¶
pars = \
{
'pop_model': 'sfe',
'pop_sed': 'eldridge2009',
'pop_fstar': 'php',
'php_func': 'dpl',
'php_func_par0': 0.05,
'php_func_par1': 1e11,
'php_func_par2': 0.5,
'php_func_par3': -0.5,
}
pop = ares.populations.GalaxyPopulation(**pars)
MUV = np.linspace(-24, -10)
pl.semilogy(MUV, pop.LuminosityFunction(4, MUV))
To compare to the observed galaxy luminosity function
obslf = ares.analysis.ObservedLF()
obslf.Plot(z=4, round_z=0.3)
The round_z makes it so that any dataset available in the range \(3.7 \leq z \leq 4.3`\) gets included in the plot.
Extrapolation options¶
It’s fairly easy to augment the double power-law used in the previous example. ‘php_faux{0}[0]’: ‘pl’, ‘php_faux_var{0}[0]’: ‘mass’, ‘php_faux_meth{0}[0]’: ‘add’, ‘php_faux_par0{0}[0]’: 0.005, ‘php_faux_par1{0}[0]’: 1e9, ‘php_faux_par2{0}[0]’: 0.01, ‘php_faux_par3{0}[0]’: 1e10,
| Dimension | \(f_{\ast}(M,z)\) options | ||
|---|---|---|---|
| logM | poly |
lognormal |
|
| (1+z) | poly |
linear_t |
constant |
| Dimension | \(L_h(M_h)\) options | ||
|---|---|---|---|
| logM | poly |
pl |
|
| (1+z) | poly |
linear_t |
constant |
Parameterized Halo Properties (PHPs)¶
In general, we can use the same approach outlined above to parameterize other quantities as a function of halo mass and/or redshift.
pars = \
{
'pop_Tmin': 1e4,
'pop_model': 'sfe',
'pop_Macc': 'mcbride2009',
'pop_sed': 'leitherer1999',
'pop_fstar': 'php[0]',
'php_Mfun[0]': 'dpl',
'php_Mfun_par0[0]': 0.15,
'php_Mfun_par1[0]': 1e12,
'php_Mfun_par2[0]': 0.5,
'php_Mfun_par3[0]': 0.5,
'pop_fesc': 'php[1]',
'php_Mfun[1]': 'dpl',
'php_Mfun_par0[1]': 0.2,
'php_Mfun_par1[1]': 0.,
'php_Mfun_par2[1]': 0.05,
'php_Mfun_par3[1]': 0.,
'php_Mfun_par4[1]': 1e8,
}
pop = ares.populations.GalaxyPopulation(**pars)
MUV = np.linspace(-24, -10)
pl.semilogy(MUV, pop.LuminosityFunction(4, MUV))
Currently, the following parameters are supported by the PHP protocol:
pop_fstarpop_fesc