skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


This content will become publicly available on March 13, 2026

Title: 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.  more » « less
Award ID(s):
2407612 1813016
PAR ID:
10632286
Author(s) / Creator(s):
; ;
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
More Like this
  1. ; ; ; ; ; ; (, The Astrophysical Journal)
    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. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal)
    Abstract We investigate spatially resolved emission-line ratios in a sample of 219 galaxies (0.6 <z< 1.3) detected using the G102 grism on the Hubble Space Telescope Wide Field Camera 3 taken as part of the CANDELS LyαEmission at Reionization survey to measure ionization profiles and search for low-luminosity active galactic nuclei (AGN). We analyze [Oiii] and Hβemission-line maps, enabling us to spatially resolve the [Oiii]/Hβemission-line ratio across the galaxies in the sample. We compare the [Oiii]/Hβratio in galaxy centers and outer annular regions to measure ionization differences and investigate the potential of sources with nuclear ionization to host AGN. We investigate some of the individual galaxies that are candidates to host strong nuclear ionization and find that they often have low stellar mass and are undetected in X-rays, as expected for low-luminosity AGN in low-mass galaxies. We do not find evidence for a significant population of off-nuclear AGN or other clumps of off-nuclear ionization. We model the observed distribution of [Oiii]/Hβspatial profiles and find that most galaxies are consistent with a small or zero difference between their nuclear and off-nuclear line ratios, but 6%–16% of galaxies in the sample are likely to host nuclear [Oiii]/Hβthat is ∼0.5 dex higher than in their outer regions. This study is limited by large uncertainties in most of the measured [Oiii]/Hβspatial profiles; therefore, deeper data, e.g., from deeper HST/WFC3 programs or from JWST/NIRISS, are needed to more reliably measure the spatially resolved emission-line conditions of individual high-redshift galaxies. 
    more » « less
  3. ; ; ; ; (, Astronomy & Astrophysics)
    We present a kinematic analysis based on the large integral field spectroscopy (IFS) dataset of SDSS-IV MaNGA (Sloan Digital Sky Survey/Mapping Nearby Galaxies at Apache Point Observatory; ∼10 000 galaxies). We have compiled a diverse sample of 594 unique active galactic nuclei (AGNs), identified through a variety of independent selection techniques, encompassing radio (1.4 GHz) observations, optical emission-line diagnostics (BPT), broad Balmer emission lines, mid-infrared colors, and hard X-ray emission. We investigated how ionized gas kinematics behave in these different AGN populations through stacked radial profiles of the [O III] 5007 emission-line width across each AGN population. We contrasted AGN populations against each other (and non-AGN galaxies) by matching samples by stellar mass, [O III] 5007 luminosity, morphology, and redshift. We find similar kinematics between AGNs selected by BPT diagnostics compared to broad-line-selected AGNs. We also identify a population of non-AGNs with similar radial profiles as AGNs, indicative of the presence of remnant outflows (or fossil outflows) of past AGN activity. We find that purely radio-selected AGNs display enhanced ionized gas line widths across all radii. This suggests that our radio-selection technique is sensitive to a population in which AGN-driven kinematic perturbations have been active for longer durations (potentially due to recurrent activity) than in purely optically selected AGNs. This connection between radio activity and extended ionized gas outflow signatures is consistent with recent evidence that suggests radio emission (expected to be diffuse) originated due to shocks from outflows. We conclude that different selection techniques can trace different AGN populations not only in terms of energetics but also in terms of AGN evolutionary stages. Our results are important in the context of the AGN duty cycle and highlight integral field unit data’s potential to deepen our knowledge of AGNs and galaxy evolution. 
    more » « less
  4. ; ; ; ; ; ; ; ; (, The Astrophysical Journal)
    Abstract Using deep near-infrared Keck/MOSFIRE observations, we analyze the rest-optical spectra of eight star-forming galaxies in the COSMOS and GOODS-N fields. We reach integration times of ∼10 hr in the deepest bands, pushing the limits on current ground-based observational capabilities. The targets fall into two redshift bins, of five galaxies atz∼ 1.7 and three galaxies atz∼ 2.5, and were selected as likely to yield significant auroral-line detections. Even with long integration times, detection of the auroral lines remains challenging. We stack the spectra together into subsets based on redshift, improving the signal-to-noise ratio on the [Oiii]λ4364 auroral emission line and, in turn, enabling a direct measurement of the oxygen abundance for each stack. We compare these measurements to commonly employed strong-line ratios alongside measurements from the literature. We find that the stacks fall within the distribution ofz> 1 literature measurements, but a larger sample size is needed to robustly constrain the relationships between strong-line ratios and oxygen abundance at high redshift. We additionally report detections of [Oi]λ6302 for nine individual galaxies and composite spectra of 21 targets in the MOSFIRE pointings. We plot their line ratios on the [Oiii]λ5008/Hβversus [Oi]λ6302/Hαdiagnostic diagram, comparing our targets to local galaxies and Hiiregions. We find that the [Oi]/Hαratios in our sample of galaxies are consistent with being produced in gas ionized byα-enhanced massive stars, as has been previously inferred for rapidly forming galaxies at early cosmic times. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal)
    Abstract Quasars atz≳ 1 most often have redshifts measured from rest-frame ultraviolet emission lines. One of the most common such lines, Civλ1549, shows blueshifts up to ≈5000 km s−1and in rare cases even higher. This blueshifting results in highly uncertain redshifts when compared to redshift determinations from rest-frame optical emission lines, e.g., from the narrow [Oiii]λ5007 feature. We present spectroscopic measurements for 260 sources at 1.55 ≲z≲ 3.50 having −28.0 ≲Mi≲ − 30.0 mag from the Gemini Near Infrared Spectrograph–Distant Quasar Survey (GNIRS-DQS) catalog, augmenting the previous iteration, which contained 226 of the 260 sources whose measurements are improved upon in this work. We obtain reliable systemic redshifts based on [Oiii]λ5007 for a subset of 121 sources, which we use to calibrate prescriptions for correcting UV-based redshifts. These prescriptions are based on a regression analysis involving Civfull-width-at-half-maximum intensity and equivalent width, along with the UV continuum luminosity at a rest-frame wavelength of 1350 Å. Applying these corrections can improve the accuracy and the precision in the Civ-based redshift by up to ∼850 km s−1and ∼150 km s−1, respectively, which correspond to ∼8.5 and ∼1.5 Mpc in comoving distance atz= 2.5. Our prescriptions also improve the accuracy of the best available multifeature redshift determination algorithm by ∼100 km s−1, indicating that the spectroscopic properties of the Civemission line can provide robust redshift estimates for high-redshift quasars. We discuss the prospects of our prescriptions for cosmological and quasar studies utilizing upcoming large spectroscopic surveys. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email