Black Hole Populations

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 The Metagalactic X-ray Background.