UV Field

The UV radiation field used in the chemistry solver can be specified via the UV_field parameter. The possible options are described in detail below.

UV Field Description
None
No UV radiation field is used.
HM01
Uses the extragalactic UV background from Haardt & Madau (2001). Note
that chimes-data currently only includes the cross-sections data at
redshift zero for this UVB. The normalisation of this radiation field
from the cross sections table is multiplied by the
radiation_field_normalisation_factor from the parameter file.
HM12
Uses the extragalactic UV background from Haardt & Madau (2012). It will
interpolate the redshift-dependent cross sections and radation field
strength from the HM12 cross sections tables in chimes-data to the
current redshift as given by the redshift parameter. If
redshift > reionisation_redshift, the UVB is set to zero.
The normalisation of this radiation field from the cross sections table
is multiplied by the radiation_field_normalisation_factor from
the parameter file.
FG20
Uses the extragalactic UV background from Faucher-Giguere (2020). It will
interpolate the redshift-dependent cross sections and radation field
strength from the FG20 cross sections tables in chimes-data to the
current redshift as given by the redshift parameter. If
redshift > reionisation_redshift, the UVB is set to zero.
The normalisation of this radiation field from the cross sections table
is multiplied by the radiation_field_normalisation_factor from
the parameter file.
B87
Uses the interstellar radiation field in the local solar neighbourhood in
the Milky Way, from Black (1987). The normalisation of this radiation
field from the cross sections table is multiplied by the
radiation_field_normalisation_factor from the parameter file.
Colibre
Uses the radiation field model developed for the Colibre simulations. In
brief, this uses the SP20 redshift-dependent extragalactic UV background
plus the interstellar radiation field (ISRF) from Black (1987) scaled
relative to the ISRF in the Milky Way based on the Jeans column density.
This is based on the model of Ploeckinger & Schaye 2020, albeit with
some modifications. The radiation_field_normalisation_factor
parameter is not used here. Instead, the ISRF component can be
re-normalised using the colibre_scale_MW_ISRF parameter. Colibre
uses a fiducial value of 0.01 for this parameter.
StellarFluxes
Uses the redshift-dependent FG20 extragalactic UV background, plus the
stellar fluxes from the star particles using the UV spectra from
Starburst 99 models (Leitherer et al. 2014) in 8 stellar age bins. See
Richings et al. (in prep) for details. Note that the
radiation_field_normalisation_factor parameter is not used here.
S04
Uses the average quasar UV spectrum from Sazonov et al. (2004). The
normalisation of the spectrum is determined by the bolometric AGN
luminosity, specified via the bolometric_AGN_luminosity_cgs
parameter, and the distance to the AGN. If IO_mode is set to
grid, the distance is specified via the distance_to_AGN_kpc
parameter. If IO_mode is set to snapshot, we instead specify
the position of the AGN via the AGN_position_x_kpc,
AGN_position_y_kpc and AGN_position_z_kpc parameters. The
distance from the AGN to each gas particle is then calculated separately.