Identifying Doppelganger Active Galactic Nuclei across redshifts from spectroscopic surveys

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Hauptverfasser: Sareen, Shreya, Panda, Swayamtrupta
Format: Preprint
Veröffentlicht: 2025
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author Sareen, Shreya
Panda, Swayamtrupta
author_facet Sareen, Shreya
Panda, Swayamtrupta
contents Active Galactic Nuclei (AGNs) are among the most luminous objects in the universe, making them valuable probes for studying galaxy evolution. However, understanding how AGN properties evolve over cosmic time remains a fundamental challenge. This study investigates whether AGNs at low redshift (nearby) can serve as proxies for their high-redshift (distant) counterparts by identifying spectral 'doppelgängers', AGNs with remarkably similar emission line properties despite being separated by vast cosmic distances. We analyze key spectral features of bona fide AGNs using the Sloan Digital Sky Survey's Data Release 16, including continuum and emission lines: Nitrogen (N V), Carbon (C IV), Magnesium (Mg II), Hydrogen-beta (H$β$), and Iron (Fe II - optical and UV) emission lines. We incorporated properties such as equivalent width, velocity dispersion in the form of full width at half maximum (FWHM), and continuum luminosities (135nm, 300nm, and 510nm) closest to these prominent lines. Our initial findings suggest the existence of multiple AGNs with highly similar spectra, hinting at the possibility that local AGNs may indeed share intrinsic properties with high-redshift ones. We showcase here one of the better candidate pairs of AGNs resulting from our analyses.
format Preprint
id arxiv_https___arxiv_org_abs_2505_01642
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Identifying Doppelganger Active Galactic Nuclei across redshifts from spectroscopic surveys
Sareen, Shreya
Panda, Swayamtrupta
Astrophysics of Galaxies
Instrumentation and Methods for Astrophysics
Machine Learning
Active Galactic Nuclei (AGNs) are among the most luminous objects in the universe, making them valuable probes for studying galaxy evolution. However, understanding how AGN properties evolve over cosmic time remains a fundamental challenge. This study investigates whether AGNs at low redshift (nearby) can serve as proxies for their high-redshift (distant) counterparts by identifying spectral 'doppelgängers', AGNs with remarkably similar emission line properties despite being separated by vast cosmic distances. We analyze key spectral features of bona fide AGNs using the Sloan Digital Sky Survey's Data Release 16, including continuum and emission lines: Nitrogen (N V), Carbon (C IV), Magnesium (Mg II), Hydrogen-beta (H$β$), and Iron (Fe II - optical and UV) emission lines. We incorporated properties such as equivalent width, velocity dispersion in the form of full width at half maximum (FWHM), and continuum luminosities (135nm, 300nm, and 510nm) closest to these prominent lines. Our initial findings suggest the existence of multiple AGNs with highly similar spectra, hinting at the possibility that local AGNs may indeed share intrinsic properties with high-redshift ones. We showcase here one of the better candidate pairs of AGNs resulting from our analyses.
title Identifying Doppelganger Active Galactic Nuclei across redshifts from spectroscopic surveys
topic Astrophysics of Galaxies
Instrumentation and Methods for Astrophysics
Machine Learning
url https://arxiv.org/abs/2505.01642