Introducing the FLAMINGOS-2 split-K medium-band filters: The impact on photometric selection of high-z galaxies in the FENIKS-pilot survey

James Esdaile*, Ivo Labbé, Karl Glazebrook, Jacqueline Antwi-Danso, Casey Papovich, Edward Taylor, Z. Cemile Marsan, Adam Muzzin, Caroline M. S. Straatman, Danilo Marchesini, Ruben Diaz, Lee Spitler, Kim-Vy H. Tran, Stephen Goodsell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Deep near-infrared photometric surveys are efficient in identifying high-redshift galaxies, however, they can be prone to systematic errors in photometric redshift. This is particularly salient when there is limited sampling of key spectral features of a galaxy's spectral energy distribution (SED), such as for quiescent galaxies where the expected age-sensitive Balmer/4000 Å break enters the K-band at z > 4. With single-filter sampling of this spectral feature, degeneracies between SED models and redshift emerge. A potential solution to this comes from splitting the K band into multiple filters. We use simulations to show an optimal solution is to add two medium-band filters, Kblue cen= 2.06 μm, Δλ = 0.25 μm) and Kred cen= 2.31 μm, Δλ = 0.27 μm), that are complementary to the existing Ks filter. We test the impact of the K-band filters with simulated catalogs comprised of galaxies with varying ages and signal-to-noise. The results suggest that the K-band filters do improve photometric redshift constraints on z > 4 quiescent galaxies, increasing precision and reducing outliers by up to 90%. We find that the impact from the K-band filters depends on the signal-to-noise, the redshift, and the SED of the galaxy. The filters we designed were built and used to conduct a pilot of the FLAMINGOS-2 Extragalactic Near-Infrared K-band Split survey. While no new z > 4 quiescent galaxies are identified in the limited area pilot, the Kblue and Kred filters indicate strong Balmer/4000 Å breaks in existing candidates. Additionally, we identify galaxies with strong nebular emission lines, for which the K-band filters increase photometric redshift precision and in some cases indicate extreme star formation.

Original languageEnglish
Article number225
Pages (from-to)1-22
Number of pages22
JournalAstronomical Journal
Issue number6
Publication statusPublished - 1 Dec 2021


  • Galaxy evolution (594)
  • High-redshift galaxies (734)
  • Photometry (1234)


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