Research Blog
Welcome to my Research Blog.
This is mostly meant to document what I am working on for myself, and to communicate with my colleagues. It is likely filled with errors!
This project is maintained by ndrakos
So far I have positions, redshifts and masses for the galaxies in the mock survey. Here are my notes on how to assign galaxy properties, following the procedure from Williams et al. 2018.
My method for obtaining galaxy counts is roughly finished (with some things to sort out).
One thing I need to decide how to divide star forming and quiescent galaxies. It is straightforward to determine the number of galaxies that should be quiescent versus star forming as a function of redshift, but I might want to take into account environmental effects.
The next step in Williams is to use redshift and stellar mass to assign integrated galaxy properties for star-forming galaxies, including the UV absolute magnitude, \(M_{\rm UV}\), and the continuum slope, \(\beta\).
In Williams et al. 2018., they typically assigned values based on 3D-HST data when available, and otherwise sample from the relations outlined below. I will start by sampling the properties for all the galaxies, and then consider using the HST data after this is working.
The \(M_{\rm UV}\)–\(M_*\) relation is modelled as a linear relationship. The slope is fixed to \(-1.66\), and the intercept of the \(M_{\rm UV}\)–\(M_*\) relation is given in Equations 11-12. They found the scatter is constant in both stellar mass and redshift, and use a Gaussian scatter of \(\sigma_{UV}=0.7\)
The rest frame UV continuum slope, \(\beta\), is defined as \(f_{\lambda}\propto \lambda^{\beta}\).
They model \(\beta\)—\(M_{\rm UV}\) relation as a linear function. Equation 13 has equations for slope and interecept (the relation doesn’t evolve after redshift 8). All mock galaxies are assigned \(\beta\) based on this mean relationship, and the intrinsic scatter \(\sigma_{\beta}=0.35\). They also truncate the distribution at \(\beta=-2.6\).
Next, they assigned spectra that are consistent with the integrated properties.
First, they created a parent mock catalog of SEDs to sample from; they used HST data where available, and otherwise created the parent sample from BEAGLE. For now, I will just be using BEAGLE.
Details are in Section 3.4.3 for star-forming galaxies and 4.2 for quiescent galaxies.
They find the closest match between the mock galaxy properties and those of the parent catalog galaxies.
Details are in Section 3.4.4 for star-forming galaxies and 4.2 for quiescent galaxies.
They assigned sizes, shapes and sersic indicies by drawing from distributions, as described in Section 5.