2022/01/18 by Julia M. Comerford, James Negus, R. Scott Barrows +4
Chemistry · Physics and Astronomy · #Active galactic nucleus #Astronomy #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics #Chemistry #Emission spectrum #Extragalactic astronomy #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Luminosity #Luminous infrared galaxy #Observatory #Physics #Spectral line #Spectroscopy #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/ac496a
20 pages, 5 figures, accepted for publication in ApJ
arxiv created 2022/01/18 · openalex publication_date 2022/03/01 · openalex created_date 2022/03/05 · arxiv updated 2022/03/09 · openalex updated_date 2026/08/05
Abstract While emission line flux ratio diagnostics are the most common technique for identifying active galactic nuclei (AGNs) in optical spectra, applying this approach to single-fiber spectra of galaxies can omit entire subpopulations of AGNs. Here, we use spatially resolved spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to construct a sample of 10 galaxies where Baldwin–Philips–Terlevich line flux ratio diagnostics classify each galaxy’s central 3″ spectrum as LINER or star-forming, while >10% of the spaxels in the galaxy’s MaNGA footprint are classified as Seyfert. We obtain Chandra observations of these 10 galaxies with off-nuclear Seyfert regions to determine whether AGNs are actually present in them. Our main result is that 7–10 (depending on strictness of criteria) of the galaxies host one or more X-ray AGNs, even though none of them were classified as AGNs based on their single-fiber optical spectra. We find that these AGNs were not identified in the single-fiber spectra because they are AGNs in the nuclei of companion galaxies, low-luminosity AGNs, dust-obscured AGNs, and/or flickering AGNs. In summary, we find that off-nuclear AGN signatures may increase the number of known AGNs by a factor of two over what conventional single nuclear fiber spectra identify. Our results show that spatially resolved spectroscopy can be leveraged to reveal a more complete census of AGNs that are traditionally missed by single-fiber spectra.