Avoiding (photo-z) Catastrophe

Research Notes of the AAS, vol. 9, pp. 157

Abstract

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 Å absorption feature, and (3) implement uncertainty floors to account for limitations in spectral models and also on the photometry itself.

Authors 4

1. Andrew J Battisti corresponding

   Australian National University · The University of Western Australia · International Centre for Radio Astronomy Research

   Affiliation as printed

   International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; andrew.battisti@uwa.edu.au

   Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611, Australia

2. Elisabete da Cunha

   The University of Western Australia · International Centre for Radio Astronomy Research

   Affiliation as printed

   International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; andrew.battisti@uwa.edu.au

3. Shuowen Jin

   DTU Space · Technical University of Denmark

   Affiliation as printed

   Cosmic Dawn Center (DAWN), Denmark

   DTU Space, Technical University of Denmark, Elektrovej 327, DK-2800 Kgs. Lyngby, Denmark

4. Jacqueline Hodge Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, NL-2300 RA Leiden, The Netherlands