Avoiding (photo-$z$) Catastrophe

TL;DR

This paper discusses the limitations of spectral energy distribution modeling in estimating galaxy redshifts, emphasizing strategies to avoid catastrophic failures by using comprehensive data and flexible models.

Contribution

It proposes improved photo-$z$ fitting methods that incorporate full SED data, flexible dust models, and uncertainty floors to mitigate degeneracy-induced errors.

Findings

Highlighting a case where photo-$z$ misclassified a galaxy due to degeneracies.

Recommending the use of entire SED data to improve redshift estimates.

Suggesting flexible dust attenuation models and uncertainty floors to reduce catastrophic failures.

Abstract

Spectral modeling codes that estimate photometric redshifts (photo-$z$) are a powerful and often reliable method for determining redshifts of galaxies. However, there are notable instances where degeneracies in spectral energy distribution (SED) colors lead to `catastrophic' failures. We highlight the case of COSBO-7, a dusty, intermediate-$z$ galaxy that masqueraded as a high-$z$ source, because it demonstrates a unique scenario where photo-$z$ codes run into issues despite extensive multi-wavelength photometry. We advocate that photo-$z$ fitting should aim to: (1) use the entire available SED (UV--radio) whenever possible to help break color degeneracies, (2) allow flexible dust attenuation prescriptions, both in terms of the attenuation curve slope and a varying 2175{\AA} absorption feature, and (3) implement uncertainty floors to account for limitations in spectral models and also on the photometry itself.