Source & Spectrum Parameters¶
Below, we list the parameters that govern the bolometric luminosity of sources as well as their spectral energy distribution. These parameters are relevant to point sources (via the source_*
parameters), as well as populations of sources used in global 21-cm signal and/or meta-galactic radiation background calculations (simply replace source_
with pop_
).
Source Luminosity¶
source_type
Options:
star
: characterized by its temperature,source_temperature
, and ionizing photon luminosity,source_qdot
bh
: characterized by its mass,source_mass
etc.toy
: completely parameterized
source_temperature
If
source_type
isstar
, this is its surface temperature. [Kelvin]Default: \(10^5 \ \text{K}\)
source_mass
If
source_type
isbh
, this is its mass [\(M_{\odot}\)]Default: \(10 \ M_{\odot}\)
source_qdot
For toy radiation source, this is the ionizing photon luminosity. [\(\text{s}^{-1}\)]
Default: \(5 \times 10^{48}\ \text{s}^{-1}\)
source_lifetime
Time after which radiation from this source will no longer be considered.
Default: \(10^{10}\) [
time_units
]
The Source Spectrum¶
We’ll use \(I_E\) to denote to the SED of sources, which the user supplies via the parameter source_sed
or pop_sed
. It is proportional
to the energy emitted at energy \(E\), NOT the number of photons
emitted at energy \(E\), and is normalized (automatically by ARES) such that
where the luminosity on the right-hand side is that determined by one of the parameters above (e.g., the Eddington luminosity of a source_mass
\(M_{\odot}\) BH) or for source populations via the pop_rad_yield
parameter. This auto-normalization guarantees the radiative yield of a single source (or source population) at some photon energy is equal to its bolometric luminosity times \(I_E\).
We use square brackets on this page to denote the units of parameters.
source_sed
Options:
'bb'
: blackbody'pl'
: power-law'mcd'
; Multi-color disk (Mitsuda et al. 1984)'simpl'
: SIMPL Comptonization model (Steiner et al. 2009)'qso'
: Quasar template spectrum (Sazonov et al. 2004)
source_Emin
Minimum photon energy to consider in radiative transfer calculation.
Default: 200 [eV]
source_Emax
Maximum photon energy to consider in radiative transfer calculation.
Default: 3e4 [eV]
source_EminNorm
Minimum photon energy to consider in normalization.
Default: 200 [eV]
source_EmaxNorm
Maximum photon energy to consider in normalization.
Default: 3e4 [eV]
source_alpha
Power-law index of emission. Only used if
source_type
ispl
orsimpl
. Defined such that \(I_{\nu} \propto \nu^{\alpha}\).Default: -1.5
Recall that \(I_{\nu}\) is proportional to the energy, not the number of photons, emitted at frequency \(\nu\).
source_logN
Base-10 logarithm of the neutral absorbing column in units of \(\text{cm}^{-2}\).
Default: \(-\infty\)
source_hardening
For non-zero absorbing columns, this parameter determines whether or not the column is applied before or after normalizing the source’s luminosity.
Default:
extrinsic
source_Rmax
If
source_type
is ‘mcd’, this parameter sets the maximum size of the accretion disk being considered.Default: 1000 [gravitational radii, \(R_g = G M_{\bullet} / c^2\), where \(M_{\bullet}\) is the black hole mass]