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Nebular Emission

Emission Line Fluxes for v2.2.1 (June 2021)

 BPASS generates the expected spectral energy distributions from stellar populations with known age and properties. It does not explicitly include nebular emission components. For this, reprocessing through a radiative transfer code such as Cloudy is required.

Cloudy is a complex code with a great many free parameters. We are not experts on its use and cannot guarantee that any set of input parameters will lead to physically realistic output parameters. We are happy to receive feedback on the following files.

Nonetheless, due to frequent requests, we make available a set of Cloudy-processed BPASS files as follows:

A nebular gas cloud with log(nH/cm-3)=2.3 and spherical geometry has been irradiated by BPASS spectra of known age and stellar metallicity, with a cloudy configuration as given at bottom of the page. All spectra are drawn from BPASS v.2.2.1, include binaries, and use imf135_300. We probe ionization parameters from logU = -1.0 to -4.0, and calculate models with the effects of interstellar grains "on" or "off". Separate Cloudy runs are required at each age step.


The file contains Cloudy-processed BPASS continuum and emission line outputs. We also have BPASS formated SED and line files as well as luminosities and equivalent widths for key emission lines.

Note that Cloudy renormalises its input spectra so output line luminosities are not reliably related to the normalisation of the stellar spectrum. To address this, we also provide reprocessed outputs renormalised to match BPASS mass/luminosity inputs. Line emission has been inserted with a single-angstrom width at its rest wavelength and these spectra should be smoothed to match spectral resolution of observations.

Cloudy Configuration

Electron density: 200 cm-3
ionization parameters, logU=[-1.0,-1.5,-2.0,-2.5,-3.0,-3.5,-4.0]
grains : on or off

Standard BPASS metallicity compositions (all abundances scale relative to Solar)
sphere (spherical geometry)
covering factor 1.0 linear
iterate to convergence
stop temperature 100K (stopping conditions)
stop efrac -2

All other parameters set to default.

File label key:
Files are labeled as "_v10a", "_v11g" etc where the version numbers relate to ionization parameter and grains as below:

ver logden covfrac grains logU Z
10a 2.3 1.0 Y -1.0 zem5-0.40 (bin)
10b 2.3 1.0 Y -1.5 zem5-0.40 (bin)
10c 2.3 1.0 Y -2.0 zem5-0.40 (bin)
10d 2.3 1.0 Y -2.5 zem5-0.40 (bin)
10e 2.3 1.0 Y -3.0 zem5-0.40 (bin)
10f 2.3 1.0 Y -3.5 zem5-0.40 (bin)
10g 2.3 1.0 Y -4.0 zem5-0.40 (bin)

version 11a-g are identical but not including dust grain depletion.

Please cite the v2.2 paper (Stanway & Eldridge 2018) and the BPASS webpage) 


Emission Line Fluxes for v2.1

In Xiao, Stanway & Eldridge (2018, MNRAS, 477, 904) we have investigated the nebular emission lines that arise from our model stellar populations in greater detail. We present the collated models used in that paper here.

The README PDF and tar files of the optical and UV emission lines can be found at this link:


Other emission lines not included in these files can be obtained by contacting Dr Xiao directly.


Note: Unfortunately, figure B1 in Xiao et al went to press with incorrect axis labels. This plot shows CIV/HeII, not [CIII]/HeII. Our apologies for any confusion this has caused. 



Nebula Emission Line Fluxes - v2.0

BPASS produces stellar continuum emission. We caution that, in astrophysical contexts, this is reprocessed by dust and nebular gas before detection, and that our models should be similarly processed.

We recommend the use of a radiative transfer code such as CLOUDY or MAPPINGS to do this.

We have been wary of providing a processed data set, since there is considerable uncertainty on the physical range of nebular gas parameters and it is important to distinguish between uncertainties in the stellar models and those in their later reprocessing.

In published work (e.g. Stanway et al 2014) and our earlier work on BPASS v1.1 (below) we have used CLOUDY v13.03 and defined a default set of nebular gas parameters as follows:

  • gas metallicity follows stellar metallicity,
  • log(electron density)=2,
  • covering fraction=1,
  • spherical geometry, inner radius=10 pc.

Input files for CLOUDY with these parameters can be generated in IDL using this code. The code can be modified for other gas properties as required.

Nebula Emission Line Fluxes - v1.1

Nebula emission line fluxes versus age for different metallicities and single/binary populations, calculated by Cloudy.



Stellar Emission Line Fluxes - v1.1

Stellar emission line fluxes versus age for different metallicities and single/binary populations, calculated from the models. Included as equivalent widths and line luminosities for C(IV), He(II) and the Wolf-Rayet Blue & Red bumps.




License: The results from BPASS and CURVEPOPS available on this site licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.


Creative Commons License


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