Spectral Energy Distribution Parameters

Blast currently uses the Prospector-\(\alpha\) model to model galaxy SEDs. To add your own model, please get in touch and consult the Developer Guide! Via the webpages, we report full posterior chains for the following parameters.

Prospector-\(\alpha\) Parameters

Prospector-\(\alpha\) parameters in the output parameter files are labeled as follows:

  • logmass, \(\log_{10}(M_{\ast}/M_{\odot})\): Logarithm of the stellar mass.

  • logzsol, \(\log_{10}(Z_{\ast}/Z_{\odot})\): Logarithm of the stellar metallicity.

  • logsfr_ratios, \(\Delta\log_{10}(\text{SFR})_{1:6}\): Difference in star formation rate (\(log_{10}(SFR)\)) between adjacent bins of the binned star formation history. This SFH model is described in Leja et al. (2019a). The binning is done in lookback time from the galaxy’s redshift. The two most recent bins cover [0,30] Myr and [30,100] Myr. The oldest bin covers \([0.85, 1.0] \times t_{age}(z)\), i.e., the first 15% of the galaxy’s life. The remaining bins are spaced logarithmically in lookback time. There are normally 7 bins in total, including the three fixed ones, giving 6 parameters. The web pages give the SFH in binned star-formation rate.

  • dust2, \(\tau_2\): The optical depth of the diffuse dust in the galaxy. The dust treatment follows a two-component Charlot & Fall (2000) model where most stars are affected by diffuse dust attenuation, but young stars also see birth cloud dust.

  • dust_index, \(\delta\): The power law index of a modified Calzetti (2000) dust attenuation law. The power law modification is by Noll et al. (2009). The UV bump strength is tied to the slope following Kriek & Conroy (2013).

  • dust1_fraction, \(\tau_1/\tau_2\): The optical depth of the birth cloud dust attenuation (as a fraction of dust2). This only affects stars younger than 10 Myr. Again, this is from the Charlot & Fall (2000) model.

  • log_fagn, \(\log_{10}(f_\text{AGN})\): Logarithm of the fraction of bolometric luminosity that is due to AGN emission using the Nenkova et al. (2008a, 2008b) CLUMPY models. This is described in detail in Leja et al. (2018).

  • log_agn_tau: \(\ln(\tau_\text{AGN})\), the optical depth (at 5500 Å) of a dust clump in the AGN torus. Again, see Leja et al. (2018) and the Nenkova et al. (2008a, 2008b) templates.

  • gas_logz, \(\log_{10}(Z_\text{gas}/Z_\odot)\): Logarithm of the gas phase metallicity.

  • duste_qpah, \(Q_\text{PAH}\): Fraction of dust mass in polycyclic aromatic hydrocarbons (PAHs). This parameter, along with the duste_umin and log_duste_gamma parameters, relate to the Draine & Li (2007) silicate-graphite polycyclic aromatic hydrocarbon (PAH) dust emission model.

  • duste_umin, \(U_\text{min}\): Minimum starlight intensity that the dust grains are exposed to.

  • log_duste_gamma, \(\log_{10}(\gamma_e)\): Fraction of dust mass exposed to starlight of minimum intensity.