Fe II Emission In Active Galactic Nuclei: The Role Of Total And Gas-Phase Iron Abundance

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dc.contributor.utaustinauthorShields, Gregory A.en_US
dc.contributor.utaustinauthorLudwig, Randi R.en_US
dc.contributor.utaustinauthorSalviander, Sarahen_US
dc.creatorShields, Gregory A.en_US
dc.creatorLudwig, Randi R.en_US
dc.creatorSalviander, Sarahen_US
dc.date.accessioned2016-04-28T19:39:00Z
dc.date.available2016-04-28T19:39:00Z
dc.date.issued2010-10en
dc.description.abstractActive galactic nuclei (AGNs) have Fe II emission from the broad-line region (BLR) that differs greatly in strength from object to object. We examine the role of the total and gas-phase iron abundance in determining Fe II strength. Using AGN spectra from the Sloan Digital Sky Survey (SDSS) in the redshift range of 0.2 < z < 0.35, we measure the Fe/Ne abundance of the narrow-line region (NLR) using the [Fe VII]/[Ne v] line intensity ratio. We find no significant difference in the abundance of Fe relative to Ne in the NLR as a function of Fe II/H beta. However, the [N II]/[S II] ratio increases by a factor of 2 with increasing Fe II strength. This indicates a trend in N/S abundance ratio, and by implication in the overall metallicity of the NLR gas, with increasing Fe II strength. We propose that the wide range of Fe II strength in AGN largely results from the selective depletion of Fe into grains in the low ionization portion of the BLR. Photoionization models show that the strength of the optical Fe II lines varies almost linearly with gas-phase Fe abundance, while the ultraviolet Fe II strength varies more weakly. Interstellar depletions of Fe can be as large as 2 orders of magnitude, sufficient to explain the wide range of optical Fe II strength in AGNs. This picture is consistent with the similarity of the BLR radius to the dust sublimation radius and with indications of Fe II emitting gas flowing inward from the dusty torus.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipJane and Roland Blumberg Centennial Professorship in Astronomy at the University of Texas at Austinen_US
dc.description.sponsorshipAlfred P. Sloan Foundationen_US
dc.description.sponsorshipNational Aeronautics and Space Administrationen_US
dc.description.sponsorshipNational Science Foundationen_US
dc.description.sponsorshipU.S. Department of Energyen_US
dc.description.sponsorshipJapanese Monbukagakushoen_US
dc.description.sponsorshipMax Planck Societyen_US
dc.identifierdoi:10.15781/T20N8N
dc.identifier.Filename2010_10_feiiemission.pdfen_US
dc.identifier.citationShields, Gregory A., Randi R. Ludwig, and Sarah Salviander. "Fe II emission in active galactic nuclei: the role of total and gas-phase iron abundance." The Astrophysical Journal, Vol. 721, No. 2 (Oct., 2010): 1835.en_US
dc.identifier.doi10.1088/0004-637x/721/2/1835en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/35020
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectgalaxies: activeen_US
dc.subjectquasars: generalen_US
dc.subjectblack-hole massen_US
dc.subjectoptimally emitting cloudsen_US
dc.subjectquasi-stellar objectsen_US
dc.subjectdigital sky surveyen_US
dc.subjectx-rayen_US
dc.subjectbroad emissionen_US
dc.subjectseyfert-galaxiesen_US
dc.subjectlineen_US
dc.subjectregionen_US
dc.subjectphysical conditionsen_US
dc.subjecteddington ratioen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleFe II Emission In Active Galactic Nuclei: The Role Of Total And Gas-Phase Iron Abundanceen_US
dc.typeArticleen_US

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