Black Hole PopulationsΒΆ
In these examples, we will initialize a stellar population object, defined
by the minimum virial temperature of halos in which stars form, Tmin
,
the star formation efficiency, fstar
, and other optional keyword arguments.
To begin, import ares and initialize an instance of the BlackHolePopulation class:
import ares
pop = ares.populations.BlackHolePopulation(Tmin=1e4, fstar=0.1)
Once initialized, there are several class methods available to compute the star-formation rate density (SFRD) and emissivity (in the UV and X-ray):
z = 20.
pop.AccretionRateDensity(z) # [g / ccm**3 / s]
pop.XrayLuminosityDensity(z) # [erg / ccm**3 / s]
pop.LymanWernerLuminosityDensity(z) # [erg / ccm**3 / s]
Class methods always return values in cgs units, and when applicable, volume densities are assumed to be in comoving units (in the comments above, ccm stands for co-moving centimeters).
To convert to more recognizable units, use conversion factors from ares
:
from ares.physics.Constants import rhodot_cgs
pop.SFRD(z) * rhodot_cgs # [Msun / cMpc**3 / yr]
pop.XrayLuminosityDensity(z) * cm_per_mpc**3 # [erg / cMpc**3 / s]
where Msun is solar masses, and cMpc is used to denote co-moving Megaparsecs.
Black hole models have a wider variety of behaviors available than stellar models.
To investigate the X-ray background that arises from a BH population,
see example_cxrb
.