Powerful t-SNE technique leading to clear separation of type-2 AGN and HII galaxies in BPT diagrams

Abstract

Narrow emission-line galaxies can be distinguished in the well-known BPT diagrams through narrow emission line properties. However, there are no boundaries visible to the naked eye between type-2 AGN and HII galaxies in BPT diagrams, besides the extreme dividing lines expected by theoretical photoionization models. Here, based on powerful t-SNE technique applied to the local narrow emission-line galaxies in SDSS DR15, type-2 AGN and HII galaxies can be clearly separated in the t-SNE determined two-dimensional projected map, and then the dividing lines can be mathematically determined in BPT diagrams, leading to charming harmonization of the theoretical expectations and the actual results from real observed properties. The results not only provide an interesting and robust method to determine the dividing lines in BPT diagrams through the powerful t-SNE technique, but also lead to further confirmation on previously defined composite galaxies more efficiently classified in the BPT diagram of [OIII]/H$\beta$ versus [NII]/H$\alpha$.

arXiv comment9 pages, 5 figures, accepted to be published in ApJ

References in corpus (24)

• The Host Galaxies of AGN
• Theoretical Modeling of Starburst Galaxies
• The Host Galaxies and Classification of Active Galactic Nuclei
• Observational evidence for AGN feedback in early-type galaxies
• A comprehensive classification of galaxies in the SDSS: How to tell true from fake AGN?
• Understanding Galaxy Evolution through Emission Lines
• The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA Derived Quantities, Data Visualization Tools and Stellar Library
• Semi-empirical analysis of Sloan Digital Sky Survey galaxies III. How to distinguish AGN hosts
• Cosmic Ray Acceleration at the Forward Shock in Tycho's Supernova Remnant: Evidence from Chandra X-ray Observations
• Dusty, Radiation Pressure Dominated Photoionization. II. Multi-Wavelength Emission Line Diagnostics for Narrow Line Regions
• The Data Analysis Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey: Emission-Line Modeling
• AGN Emission Line Diagnostics and the Mass-Metallicity Relation up to Redshift z~2: the Impact of Selection Effects and Evolution
• Theoretical Modeling of Star-Forming Galaxies I. Emission Line Diagnostic Grids for Local and Low-Metallicity Galaxies
• The FMOS-COSMOS survey of star-forming galaxies at z~1.6. IV: Excitation state and chemical enrichment of the interstellar medium
• Automated Classification of Stellar Spectra. II: Two-Dimensional Classification with Neural Networks and Principal Components Analysis
• Estimation of stellar atmospheric parameters from SDSS/SEGUE spectra
• PCA Tomography: how to extract information from datacubes
• Dissecting stellar chemical abundance space with t-SNE
• The Galah Survey: Classification and diagnostics with t-SNE reduction of spectral information
• An Assessment of the Energy Budgets of Low-Ionization Nuclear Emission Regions
• A probabilistic approach to emission-line galaxy classification
• Global regularities in integrated galaxy spectra
• A Method to Distinguish Quiescent and Dusty Star-forming Galaxies with Machine Learning
• Theoretical Modeling of Emission-Line galaxies: New Classification Parameters for Mid-Infrared and Optical Spectroscopy

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