Luminosity Function

In this post, I showed some preliminary predictions for the galaxy catalog.

The luminosity function (LF) didn’t look quite right, and I’m exploring that a bit more in this post.

Results

Here I have plotted it again with the Bouwens et al. 2015 luminosity functions:

Update 10/02: The Bouwens relations should have only been for z>4… see next post

$M_{\rm UV}$ assignment

First, I want to check if this is due to problems in the $M_{\rm UV}$–$M$ relation. Here are how our current mock catalog relations compare to the relations in W18:

The $M_{\rm UV}$–$M$ relation isn’t too different, but there are some discrepancies. If instead I draw $M_{\rm UV}$ properties from the W18 relations, rather than get from our SEDs, as in this post, I can plot the LF and get

This looks a bit better, but it still doesn’t match, so I don’t think our $M_{\rm UV}$ assignment is the problem.

Galaxy Completeness

The other possible problem is that the it is because the SMFs are not complete below $\approx 10^9\,M_{\odot}$ (e.g. see this post).

To test the effect of missing low mass galaxies, I again used $M_{\rm UV}$ values drawn from the W18 distribution, but I didn’t include galaxies with masses below $10^{10}\,M_{\odot}$.

This makes a very large difference on the SMF, which makes me thing this is the reason we can’t reproduce the observational LFs.

For the presentation

Ideally I would have an estimate for how well we would be able to constrain the faint end of the luminosity function, but right now I don’t have enough low mass galaxies to resolved in the simulation, and I don’t think I have enough time to analyze the high resolution simulations before the conference.

Since I don’t need spatial information from this plot, I can just generate galaxy mass/redshifts from the distributions down to lower mass resolutions, and then run them through my SED assignment code and then plot the LF.

I think W18 used a mass limit of $M_{\rm min} = 10^6$, and they were able to reproduce the LFs, so that should be enough. However, I only expect the SMFs for the $2048^3$ simulations to be complete to $\approx 10^7\,M_{\odot}$, so I will start with that mass limit. If there are issues reproducing the LFs with $M_{\rm min}=10^7\,M_{\odot}$, we might need to consider adding subhalos analytically to the catalog.

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