Classifying Intermediate Redshift Galaxies in SDSS: Alternative Diagnostic Diagrams

Abstract

We select a sample of 1,437 active galactic nuclei (AGN) from the catalog of the Sloan Digital Sky Survey (SDSS) galaxy properties from the Portsmouth group by detection of the high-ionization [Ne V] 3426 Å emission line. We compare the fluxes of [Ne III] 3869 Å, [O III] 5007 Å, [O II] 3726, 3728 Å, and [O I] 6300 Å to that of [Ne V]. All four lines show a strong linear correlation with [Ne V], although lines from ions with lower ionization potentials have a lower correlation coefficient. We investigate the use of two forbidden-line ratio (FLR) diagnostic diagrams that do not rely on H$\alpha$ in order to classify high redshift galaxies. These use the [Ne III]/[O II] line ratio plotted against [O III]/[O I] and [O III]/[O II] respectively. We use photo-ionization modeling to characterize the behavior of the narrow-line region in AGN and star-forming regions and test the validity of our diagnostic diagrams. We also use a luminosity cutoff of log L[OIII] [erg/s] = 42, which lowers the contamination of the AGN region by star-forming galaxies down to 10% but does not remove Green Pea and Purple Grape galaxies from the AGN region. We also investigate the OHNO diagram which uses [Ne III]/[O II] plotted against [O III]/H$\beta$. Using our new diagnostic diagrams, we are able to reliably classify AGN up to a redshift of z $\le$ 1.06, and add more than 822 new AGN to the [Ne V]-selected AGN sample.

arXiv commentPublished February 12 2024 in ApJ, 15 pages, 10 figures

References in corpus (44)

• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• The Host Galaxies of AGN
• Theoretical Modeling of Starburst Galaxies
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
• The SAURON project - V. Integral-field emission-line kinematics of 48 elliptical and lenticular galaxies
• Observational evidence for AGN feedback in early-type galaxies
• Galaxy Zoo Green Peas: Discovery of A Class of Compact Extremely Star-Forming Galaxies
• [OII] as a Star Formation Rate Indicator
• Evidence for TP-AGB stars in high redshift galaxies, and their effect on deriving stellar population parameters
• Semi-empirical analysis of Sloan Digital Sky Survey galaxies III. How to distinguish AGN hosts
• The Origin and Optical Depth of Ionizing Radiation in the "Green Pea" Galaxies
• Stellar velocity dispersions and emission line properties of SDSS-III/BOSS galaxies
• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• A New Diagnostic of Active Galactic Nuclei: Revealing Highly-Absorbed Systems at Redshift>0.3
• Towards a Complete Census of AGNs in Nearby Galaxies: A Large Population of Optically Unidentified AGNs
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• The bolometric luminosity of type 2 AGN from extinction-corrected [OIII]: no evidence for Eddington-limited sources
• AGN Emission Line Diagnostics and the Mass-Metallicity Relation up to Redshift z~2: the Impact of Selection Effects and Evolution
• Spitzer Uncovers Active Galactic Nuclei Missed by Optical Surveys in 7 Late-type Galaxies
• Spectral classification of emission-line galaxies from the Sloan Digital Sky Survey. I. An improved classification for high redshift galaxies
• AEGIS: Demographics of X-ray and Optically Selected AGNs
• The X-ray to [Ne V]3426 flux ratio: discovering heavily obscured AGN in the distant Universe
• Neon and Argon optical emission lines in ionized gaseous nebulae: Implications and applications
• Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. II. Physical Conditions Near the NGC 1068 ``Hot-Spot''
• Obscured AGN at z~1 from the zCOSMOS-Bright Survey I. Selection and Optical Properties of a [Ne v]-selected sample
• The High-Ionization Nuclear Emission-Line Region of Seyfert Galaxies
• Constraining the AGN Contribution in a Multiwavelength Study of Seyfert Galaxies
• Kinematics and Optical Depth in the Green Peas: Suppressed Superwinds in Candidate LyC Emitters
• [NeIII]/[OII] as an Ionization Parameter Diagnostic in Star-Forming Galaxies
• Ionization Parameter as a Diagnostic of Radiation and Wind Pressures in H II Regions and Starburst Galaxies
• [Ne V] Emission in Optically Classified Starbursts
• Evidence for a Physically Compact Narrow-Line Region in the Seyfert 1 Galaxy NGC 5548
• Assessing the sources of reionisation: a spectroscopic case study of a 30$\times$ lensed galaxy at $z\sim 5$ with Lyα, CIV, MgII, and [NeIII]
• Physical Properties of II Zw 40's Super Star Cluster and Nebula: New Insights and Puzzles from UV Spectroscopy
• Recalibration of [O II] $\lambda 3727$ as a Star Formation Rate Estimator for Active and Inactive Galaxies
• HST Emission Line Galaxies at z ~ 2: The Mystery of Neon
• The MOSDEF Survey: Neon as a Probe of ISM Physical Conditions at High Redshift
• Hubble Space Telescope Observations of [O~III] Emission in Nearby QSO2s: Physical Properties of the Ionised Outflows
• The difference between the narrow line region of Seyfert 1 and Seyfert 2 galaxies
• Strong [OIII]λ5007 emission line compact galaxies in LAMOST DR9: Blueberries, Green Peas and Purple Grapes
• Multi-wavelength Probes of Obscuration Towards the Narrow Line Region in Seyfert Galaxies
• The ROSAT Deep Survey II. Optical identification, photomettry and spectra of sources in the Lockman field

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• New AGN diagnostic diagrams based on the [OIII]$\lambda 4363$ auroral line
• EP241021a: a months-duration X-ray transient with luminous optical and radio emission
• The ALPINE-CRISTAL-JWST Survey: Revealing Less Massive Black Holes in High-Redshift Galaxies
• New Methods of Identifying AGN in the Early Universe using Spectroscopy and Photometry in the JWST Era
• Core Revelations: the Star Formation and AGN Connection at the Heart of NGC 7469
• A search for HI absorption in distant star-forming galaxies with ASKAP-FLASH -- I. Selection and analysis of the radio sample
• Boosting the evolutionary picture of Cl 0024+17 and MS 0451-03: A case study at intermediate-redshift
• Star Formation Rates in [Ne V] 3426 Å Selected Active Galactic Nuclei: Evidence for a Decrease along the Main Sequence?
• Through the fog: a complementary optical galaxy classification scheme for 'intermediate' redshifts
• Extreme equivalent width-selected low-mass starbursts at $z=4-9$: insights into their role in cosmic reionization