Photometric redshifts for galaxies in the Spitzer Extragalactic Representative Volume Survey (SERVS)

Janine Pforr*, Mattia Vaccari, Mark Lacy, Claudia Maraston, Kristina Nyland, Lucia Marchetti, Daniel Thomas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

290 Downloads (Pure)


We present photometric redshifts for ∼4 million galaxies detected in the Spitzer 3.6 or 4.5 μm bands of the Spitzer Extragalactic Representative Volume Survey (SERVS). The 18 deg2 area of SERVS covers five extragalactic fields with a variety of ancillary, optical, and near-infrared (IR) photometry. We evaluate the accuracy of our photometric redshifts with ∼90.000 publicly available, spectroscopic redshifts. Overall, we find an average of ∼0.038 for the normalized median absolute deviation (σNMAD), a measure similar to the standard deviation yet more robust against outliers, and outlier fraction η of 3.7 per cent for the sources with the widest wavelength coverage. On the example of the XMM field, we quantify the quality and reliability of photometric redshifts as a function of (1) the number of photometric bands available in the fitting, (2) iAB magnitude, (3) Infrared Array Camera (IRAC) 3.6 μm magnitude, (4) spectroscopic redshift, and (5) the survey origin of the spectroscopic redshift. The best results are achieved when the photometry available for the fitting covers rest-frame optical and near-IR wavelengths. σNMAD and η are smallest for the brightest objects. Similarly, we find σNMAD and η to be smaller on average at z < 1.5 than at z > 1.5. Photometric redshifts derived without the two IRAC filter bands, but detections in all other bands are slightly underestimated. Approximately 76 per cent of SERVS sources with at least five available filter bands lie between redshift 0 and ∼1.5.We find a tail of high-redshift galaxies, i.e. ∼7 per cent of all objects with at least five available filter bands for the fitting lie at z > 3.We discuss ways to improve upon the photometric redshifts for SERVS galaxies in the future.

Original languageEnglish
Pages (from-to)3168-3195
Number of pages28
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date23 Nov 2018
Publication statusPublished - 1 Mar 2019


  • Galaxies: distances and redshifts
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: fundamental parameters
  • Galaxies: general


Dive into the research topics of 'Photometric redshifts for galaxies in the Spitzer Extragalactic Representative Volume Survey (SERVS)'. Together they form a unique fingerprint.

Cite this