and a 2 Gyr old population than to differentiate between a 10 Gyr and a 12 Gyr old population. We see that effect in practice in our modeling in Fig. \[fig:magr\_params\], as the posterior distribution for galaxies with young ages are usually narrower than the prior distribution, while for those with old ages we tend to obtain relatively flat posteriors. Overall, we conclude that we are able to differentiate between young and old stellar populations in our UDG candidates, which is enough to allow a broad discussion of the formation of these systems.

Finally, the quality of the modeled photometric redshifts also depends on the apparent magnitude of the UDGs. The posterior redshift distribution for the faint UDGs is very similar to the prior distribution. In these cases, the quoted uncertainties in the redshift are around $0.8$ dex, which is simply the propagation of allowed prior range. On the other hand, the bright UDGs have a narrower range of redshifts in the posterior distribution, and their median redshifts are usually smaller than the prior median of $\approx 0.02$. However, even in these cases, the redshift estimate is very uncertain, and we are only able to constrain the photometric redshift with 