CLASS Survey Description: Coronal Line Needles in the SDSS Haystack

Abstract

Coronal lines are a powerful, yet poorly understood, tool to identify and characterize Active Galactic Nuclei (AGNs). There have been few large scale surveys of coronal lines in the general galaxy population in the literature so far. Using a novel pre-selection technique with a flux-to-RMS ratio $F$, followed by Markov-Chain Monte Carlo (MCMC) fitting, we searched for the full suite of 20 coronal lines in the optical spectra of almost 1 million galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 8. We present a catalog of the emission line parameters for the resulting 258 galaxies with detections. The Coronal Line Activity Spectroscopic Survey (CLASS) includes line properties, host galaxy properties, and selection criteria for all galaxies in which at least one line is detected. This comprehensive study reveals that a significant fraction of coronal line activity is missed in past surveys based on a more limited set of coronal lines; $\sim$60% of our sample do not display the more widely surveyed [Fe X] $\lambda$6374. In addition, we discover a strong correlation between coronal line and WISE W2 luminosities, suggesting that the mid-infrared flux can be used to predict coronal line fluxes. For each line we also provide a confidence level that the line is present, generated by a novel neural network, trained on fully simulated data. We find that after training the network to detect individual lines using 100,000 simulated spectra, we achieve an overall true positive rate of 75.49% and a false positive rate of only 3.96%.

27 pages, 16 figures, 4 tables

References in corpus (17)

• Array Programming with NumPy
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• The MAPPINGS III Library of Fast Radiative Shock Models
• A 0.8-2.4 microns spectral atlas of Active Galactic Nuclei
• First look with JWST spectroscopy: $z\sim 8$ galaxies resemble local analogues
• Outflows of very ionized gas in the center of Seyfert galaxies: kinematics and physical conditions
• BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission
• A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe X] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events
• The Star Forming Main Sequence of Dwarf Low Surface Brightness Galaxies
• [Ne V] Emission in Optically Classified Starbursts
• Large Binocular Telescope observations of new six compact star-forming galaxies with [NeV] 3426A emission
• Near-Infrared Coronal Line Observations of Dwarf Galaxies hosting AGN-driven Outflows
• Relics of Supermassive Black Hole Seeds: The Discovery of an Accreting Black Hole in an Optically Normal, Low Metallicity Dwarf Galaxy
• Outflows, Shocks and Coronal Line Emission in a Radio-Selected AGN in a Dwarf Galaxy
• CLASS: Coronal Line Activity Spectroscopic Survey
• The ionised gas outflow in the Circinus galaxy: kinematics and physical conditions

Cited by in corpus (6)

• SDSS1335+0728: The awakening of a $\sim 10^6{M}_{\odot }$ black hole
• Nuclear Activity in the Low Metallicity Dwarf Galaxy SDSS J0944-0038: A Glimpse into the Primordial Universe
• X-Ray Bright Active Galactic Nuclei in Local Dwarf Galaxies: Insights from eROSITA
• Spectral variability studies in Active Galactic Nuclei: Exploring continuum and emission line regions in the age of LSST and JWST
• Emission Line Predictions for Mock Galaxy Catalogues: a New Differentiable and Empirical Mapping from DESI
• Insights for Early Massive Black Hole Growth from JWST Detection of the [Ne v] λ3427 Emission Line