.. _sed_params: Spectral Energy Distribution Parameters ======================================= Blast currently uses the Prospector-:math:`\alpha` model to model galaxy SEDs. To add your own model, please get in touch and consult the :doc:`Developer Guide `! Via the webpages, we report full posterior chains for the following parameters. Prospector-:math:`\alpha` Parameters ------------------------------------ Prospector-:math:`\alpha` parameters in the output parameter files are labeled as follows: * :code:`logmass`, :math:`\log_{10}(M_{\ast}/M_{\odot})`: Logarithm of the stellar mass. * :code:`logzsol`, :math:`\log_{10}(Z_{\ast}/Z_{\odot})`: Logarithm of the stellar metallicity. * :code:`logsfr_ratios`, :math:`\Delta\log_{10}(\text{SFR})_{1:6}`: Difference in star formation rate (:math:`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 :math:`[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. * :code:`dust2`, :math:`\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. * :code:`dust_index`, :math:`\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) `_. * :code:`dust1_fraction`, :math:`\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. * :code:`log_fagn`, :math:`\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) `_. * :code:`log_agn_tau`: :math:`\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. * :code:`gas_logz`, :math:`\log_{10}(Z_\text{gas}/Z_\odot)`: Logarithm of the gas phase metallicity. * :code:`duste_qpah`, :math:`Q_\text{PAH}`: Fraction of dust mass in polycyclic aromatic hydrocarbons (PAHs). This parameter, along with the :code:`duste_umin` and :code:`log_duste_gamma` parameters, relate to the `Draine & Li (2007) `_ silicate-graphite polycyclic aromatic hydrocarbon (PAH) dust emission model. * :code:`duste_umin`, :math:`U_\text{min}`: Minimum starlight intensity that the dust grains are exposed to. * :code:`log_duste_gamma`, :math:`\log_{10}(\gamma_e)`: Fraction of dust mass exposed to starlight of minimum intensity.