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arXiv · 1205.4764

A new infrared color criterion for the selection of 0<z<7 AGN: application to deep fields and implications for JWST surveys

Hugo Messias·Jose M. Afonso·Mara Salvato·Bahram Mobasher·Andrew M. Hopkins
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Abstract

[Abridged] It is widely accepted that observations at mid-infrared (mid-IR) wavelengths enable the selection of galaxies with nuclear activity, which may not be revealed even in the deepest X-ray surveys. In this work new near- and mid-IR color diagnostics are explored, aiming for improved efficiency - better completeness and less contamination - in selecting AGN out to very high redshifts. We restrict our study to the James Webb Space Telescope wavelength range (0.6-27um). The criteria are created based on the predictions by state-of-the-art galaxy and AGN templates covering a wide variety of galaxy properties, and tested against control samples with deep multi-wavelength coverage (ranging from the X-rays to radio frequencies). We show that the colors Ks-[4.5], [4.5]-[8.0], and [8.0]-[24] are ideal as AGN/non-AGN diagnostics at, respectively, z<~1, 1<~z<~2.5, and z>~2.5-3. However, when the source redshift is unknown, these colors should be combined. We thus develop an improved IR criterion (using Ks and IRAC bands, KI) as a new alternative at z<~2.5. KI does not show improved completeness (50-60% overall) in comparison to commonly used IRAC-based AGN criteria, but is less affected by non-AGN contamination (revealing a >50-90% level of successful AGN selection). We also propose KIM (using Ks, IRAC, and MIPS-24um bands, KIM), which aims to select AGN hosts from local distances to as far back as the end of reionization (0 70-90% level of successful AGN selection. KI and KIM are built to be reliable against a ~10-20% error in flux, are based on existing filters, and are suitable for immediate use.

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Hugo Messias, Jose M. Afonso, Mara Salvato, Bahram Mobasher, Andrew M. Hopkins. 2012-05-21. A new infrared color criterion for the selection of 0<z<7 AGN: application to deep fields and implications for JWST surveys. https://doi.org/10.1088/0004-637x/754/2/120

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