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Abstract We present a search for extreme emission line galaxies (EELGs) atz< 1 in the COSMOS and North Ecliptic Pole (NEP) fields with imaging from Subaru/Hyper Suprime-Cam (HSC) and a combination of new and existing spectroscopy. We select EELGs on the basis of substantial excess flux in thezbroad band, which is sensitive to Hαat 0.3 ≲z≲ 0.42 and [Oiii]λ5007 at 0.7 ≲z≲ 0.86. We identify 10,470 galaxies withzexcesses in the COSMOS data set and 91,385 in the NEP field. We cross-reference the COSMOS EELG sample with the zCOSMOS and DEIMOS 10k spectral catalogs, finding 1395 spectroscopic matches. We made an additional 71 (46 unique) spectroscopic measurements withY< 23 using the HYDRA multiobject spectrograph on the WIYN 3.5 m telescope, and 204 spectroscopic measurements from the DEIMOS spectrograph on the Keck II telescope, providing a total of 1441/10,470 spectroscopic redshifts for the EELG sample in COSMOS (∼14%). We confirm that 1418 (∼98%) are Hαor [Oiii]λ5007 emitters in the above stated redshift ranges. We also identify 240 redshifted Hαand [Oiii]λ5007 emitters in the NEP using spectra taken with WIYN/HYDRA and Keck/DEIMOS. Using broadband-selection techniques in theg−r−icolor space, we distinguish between Hαand [Oiii]λ5007 emitters with 98.6% accuracy. We test our EELG selection by constructing Hαand [Oiii]λ5007 luminosity functions and comparing to recent literature results. We conclude that broadband magnitudes from HSC, the Vera C. Rubin Observatory, and other deep optical multiband surveys can be used to select EELGs in a straightforward manner.
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This content will become publicly available on March 13, 2026
The Green Chile Project. I. A New Catalog of Low-redshift Extended Emission-line Nebulae
Abstract Extended emission-line nebulae (EELN) around galaxies allow us to study their host galaxies and their surrounding environments. EELN can provide insights into the physical properties of the extended gas and, when powered by active galactic nuclei (AGN), they can constrain the ionization history of the central engine as well. Of interest is a sample of low-redshift EELN powered by AGN atz ∼ 0.3 that were discovered in the Sloan Digital Sky Survey (SDSS) through color selection. Colloquially called “Green Beans,” due to strong, spatially extended [Oiii]λ5007 emission dominating ther-band flux, they have been shown to be low-redshift counterparts to higher-redshift Lyαnebulae. However, only 17 Green Bean EELN are known to exist atz ∼ 0.3, and the original color selection was subsequently found to be biased in terms of host galaxy properties. In order to mitigate these biases and expand the known sample, we have developed a new, physically motivated selection approach, based on simulated EELN atz ∼ 0.3, with well-defined physical properties ([Oiii]λ5007 rest-frame equivalent width and continuum spectral slope). With this improved selection approach, we have generated a new sample of 165 EELN candidates: the “Green Chile” catalog. Of the 13 candidates with existing SDSS/Baryon Oscillation Spectroscopic Survey spectra, we confirm that five are EELN with [Oiii]λ5007 equivalent widths >200 Å and emission-line ratios indicative of AGN powering.
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- PAR ID:
- 10632286
- Publisher / Repository:
- American Astronomical Society Journals
- Date Published:
- Journal Name:
- The Astronomical Journal
- Volume:
- 169
- Issue:
- 4
- ISSN:
- 0004-6256
- Page Range / eLocation ID:
- 207
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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