The Paschen Jump as a Diagnostic of the Diffuse Nebular Continuum Emission in Active Galactic Nuclei*
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The Paschen Jump as a Diagnostic of the Diffuse Nebular Continuum Emission in Active Galactic Nuclei*. / Guo, Hengxiao; Barth, Aaron J.; Korista, Kirk T.; Goad, Michael R.; Cackett, Edward M.; Bentz, Misty C.; Brandt, William N.; Gonzalez-Buitrago, D.; Ferland, Gary J.; Gelbord, Jonathan M.; Ho, Luis C.; Horne, Keith; Joner, Michael D.; Kriss, Gerard A.; McHardy, Ian; Mehdipour, Missagh; Park, Daeseong; Remigio, Raymond; Vivian, U.; Vestergaard, Marianne.
I: Astrophysical Journal, Bind 927, Nr. 1, 60, 01.03.2022.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - The Paschen Jump as a Diagnostic of the Diffuse Nebular Continuum Emission in Active Galactic Nuclei*
AU - Guo, Hengxiao
AU - Barth, Aaron J.
AU - Korista, Kirk T.
AU - Goad, Michael R.
AU - Cackett, Edward M.
AU - Bentz, Misty C.
AU - Brandt, William N.
AU - Gonzalez-Buitrago, D.
AU - Ferland, Gary J.
AU - Gelbord, Jonathan M.
AU - Ho, Luis C.
AU - Horne, Keith
AU - Joner, Michael D.
AU - Kriss, Gerard A.
AU - McHardy, Ian
AU - Mehdipour, Missagh
AU - Park, Daeseong
AU - Remigio, Raymond
AU - Vivian, U.
AU - Vestergaard, Marianne
PY - 2022/3/1
Y1 - 2022/3/1
N2 - Photoionization modeling of active galactic nuclei (AGN) predicts that diffuse continuum (DC) emission from the broad-line region makes a substantial contribution to the total continuum emission from ultraviolet through near-infrared wavelengths. Evidence for this DC component is present in the strong Balmer jump feature in AGN spectra, and possibly from reverberation measurements that find longer lags than expected from disk emission alone. However, the Balmer jump region contains numerous blended emission features, making it difficult to isolate the DC emission strength. In contrast, the Paschen jump region near 8200 angstrom is relatively uncontaminated by other strong emission features. Here, we examine whether the Paschen jump can aid in constraining the DC contribution, using Hubble Space Telescope Space Telescope Imaging Spectrograph spectra of six nearby Seyfert 1 nuclei. The spectra appear smooth across the Paschen edge, and we find no evidence of a Paschen spectral break or jump in total flux. We fit multicomponent spectral models over the range 6800-9700 angstrom and find that the spectra can still be compatible with a significant DC contribution if the DC Paschen jump is offset by an opposite spectral break resulting from blended high-order Paschen emission lines. The fits imply DC contributions ranging from similar to 10% to 50% at 8000 angstrom, but the fitting results are highly dependent on assumptions made about other model components. These degeneracies can potentially be alleviated by carrying out fits over a broader wavelength range, provided that models can accurately represent the disk continuum shape, Fe ii emission, high-order Balmer line emission, and other components.
AB - Photoionization modeling of active galactic nuclei (AGN) predicts that diffuse continuum (DC) emission from the broad-line region makes a substantial contribution to the total continuum emission from ultraviolet through near-infrared wavelengths. Evidence for this DC component is present in the strong Balmer jump feature in AGN spectra, and possibly from reverberation measurements that find longer lags than expected from disk emission alone. However, the Balmer jump region contains numerous blended emission features, making it difficult to isolate the DC emission strength. In contrast, the Paschen jump region near 8200 angstrom is relatively uncontaminated by other strong emission features. Here, we examine whether the Paschen jump can aid in constraining the DC contribution, using Hubble Space Telescope Space Telescope Imaging Spectrograph spectra of six nearby Seyfert 1 nuclei. The spectra appear smooth across the Paschen edge, and we find no evidence of a Paschen spectral break or jump in total flux. We fit multicomponent spectral models over the range 6800-9700 angstrom and find that the spectra can still be compatible with a significant DC contribution if the DC Paschen jump is offset by an opposite spectral break resulting from blended high-order Paschen emission lines. The fits imply DC contributions ranging from similar to 10% to 50% at 8000 angstrom, but the fitting results are highly dependent on assumptions made about other model components. These degeneracies can potentially be alleviated by carrying out fits over a broader wavelength range, provided that models can accurately represent the disk continuum shape, Fe ii emission, high-order Balmer line emission, and other components.
KW - LAG-LUMINOSITY RELATIONSHIP
KW - ACCRETION-DISK
KW - SPACE TELESCOPE
KW - BROAD EMISSION
KW - SEYFERT 1
KW - FE-II
KW - H-I
KW - QUASARS
KW - SPECTRA
KW - GALAXY
U2 - 10.3847/1538-4357/ac4bc6
DO - 10.3847/1538-4357/ac4bc6
M3 - Journal article
VL - 927
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 60
ER -
ID: 302553055