Non-Gaussian assembly bias from a semi-analytic galaxy formation model

We produce z = 1 galaxy catalogues with the semi-analytic code galacticus to study the dependence on the assembly history of the host halos of the non-Gaussian bias parameter bφ for galaxies selected by colour magnitude and emission line luminosities. Galaxies selected by g-r colour shows a large assembly bias consistent with previous analyses: a larger value of the normalization amplitude σ8 implies a faster mass assembly and therefore older and redder galaxies. For galaxies selected by H α luminosity, we do not detect a significant assembly bias for the redshift and the halo masses considered here. This indicates that the non-Gaussian assembly bias should be less of a concern for future emission line galaxy surveys. We investigate, for the first time, the sensitivity of the non-Gaussian assembly bias to a change in the parameters of the galaxy formation model: these induce variations up to order unity in the measured Δbφ, but the overall trends with colour or luminosity remain the same. Since these results may be sensitive to the specific galaxy formation model, it will be prudent to extend this analysis to other semi-analytic models in addition to halo mass and redshift.