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Introducing the FLAMINGOS-2 Split-K Medium-band Filters: The Impact on Photometric Selection of High-z Galaxies in the FENIKS-pilot survey

Esdaile, James and Labbé, Ivo and Glazebrook, Karl and Antwi-Danso, Jacqueline and Papovich, Casey and Taylor, Edward and Marsan, Z. Cemile and Muzzin, Adam and Straatman, Caroline M. S. and Marchesini, Danilo and Diaz, Ruben and Spitler, Lee and Tran, Kim-Vy H. and Goodsell, Stephen (2021) 'Introducing the FLAMINGOS-2 Split-K Medium-band Filters: The Impact on Photometric Selection of High-z Galaxies in the FENIKS-pilot survey.', The Astronomical Journal, 162 (6). p. 225.


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 (λcen = 2.06 μm, Δλ = 0.25 μm) and Kred (λcen = 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.

Item Type:Article
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Publisher statement:© 2021. The American Astronomical Society. All rights reserved.
Date accepted:24 August 2021
Date deposited:23 November 2021
Date of first online publication:03 November 2021
Date first made open access:23 November 2021

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