Photometric Redshifts with the LSST. II. The Impact of Near-infrared and Near-ultraviolet Photometry

Journal Article · Mon Jun 01 00:00:00 EDT 2020 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.3847/1538-3881/AB8A43· OSTI ID:23013228

Graham, Melissa L.; Connolly, Andrew J.; Wang, Winnie; Morrison, Christopher B.; Ivezić, Željko; Daniel, Scott F.; Jones, R. Lynne; Jurić, Mario; Yoachim, Peter; Kalmbach, J. Bryce ^[1]; Schmidt, Samuel J. ^[2]; Fabbro, Sébastien; Côté, Patrick ^[3]

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1. DiRAC Institute, Department of Astronomy, University of Washington, Box 351580, U.W., Seattle WA 98195 (United States)
2. Department of Physics, UC Davis, One Shields Avenue, Davis CA 95616 (United States)
3. National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Centre, 5071 W. Saanich Road, Victoria, BC V9E 2E7 (Canada)

Accurate photometric redshift (photo-z) estimates are essential to the cosmological science goals of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). In this work, we use simulated photometry for mock galaxy catalogs to explore how LSST photo-z estimates can be improved by the addition of near-infrared (NIR) and/or ultraviolet (UV) photometry from the Euclid, Wide-Field InfrarRed Survey Telescope (WFIRST), and/or Cosmological Advanced Survey Telescope for Optical and ultraviolet Research (CASTOR) space telescopes. Generally, we find that deeper optical photometry can reduce the standard deviation of the photo-z estimates more than adding NIR or UV filters but that additional filters are the only way to significantly lower the fraction of galaxies with catastrophically under- or overestimated photo-z. For Euclid, we find that the addition of JH 5σ photometric detections can reduce the standard deviation for galaxies with z > 1 (z > 0.3) by ∼20% (∼10%), and the fraction of outliers by ∼40% (∼25%). For WFIRST, we show how the addition of deep YJHK photometry could reduce the standard deviation by ≳50% at z > 1.5 and drastically reduce the fraction of outliers to just ∼2% overall. For CASTOR, we find that the addition of its UV- and u-band photometry could reduce the standard deviation by ∼30% and the fraction of outliers by ∼50% for galaxies with z < 0.5. We also evaluate the photo-z results within sky areas that overlap with both the NIR and UV surveys and when spectroscopic training sets built from the surveys’ small-area deep fields are used.

• OSTI ID: 23013228
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 159, Issue 6; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CATALOGS
GALAXIES
NEAR INFRARED RADIATION
NEAR ULTRAVIOLET RADIATION
PHOTOMETRY
RED SHIFT
SIMULATION
SPACE
TELESCOPES