TY - JOUR
T1 - The mid-infrared high-ionization lines from active galactic nuclei and star-forming galaxies
AU - Pereira-Santaella, Miguel
AU - Diamond-Stanic, Aleksandar M.
AU - Alonso-Herrero, Almudena
AU - Rieke, George H.
PY - 2010/12/20
Y1 - 2010/12/20
N2 - We used Spitzer/Infrared Spectrograph spectroscopic data on 426 galaxies including quasars, Seyferts, LINERs, and Hii galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne v]14.3 μm and 24.3 μm (97.1 eV) and the [Oiv]25.9 μm (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne iii]15.56 μm (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne iii] excess due to star formation in Seyfert galaxies. We also estimated the [Oiv] luminosity due to star formation in active galaxies and determined that it dominates the [Oiv] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the active galactic nucleus dominates the [Oiv] emission in most Seyfert galaxies, whereas star formation adequately explains the observed [Oiv] emission in optically classified Hii galaxies. Finally, we computed photoionization models to determine the physical conditions of the narrow-line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log nH (cm-2) < 21.
AB - We used Spitzer/Infrared Spectrograph spectroscopic data on 426 galaxies including quasars, Seyferts, LINERs, and Hii galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne v]14.3 μm and 24.3 μm (97.1 eV) and the [Oiv]25.9 μm (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne iii]15.56 μm (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne iii] excess due to star formation in Seyfert galaxies. We also estimated the [Oiv] luminosity due to star formation in active galaxies and determined that it dominates the [Oiv] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the active galactic nucleus dominates the [Oiv] emission in most Seyfert galaxies, whereas star formation adequately explains the observed [Oiv] emission in optically classified Hii galaxies. Finally, we computed photoionization models to determine the physical conditions of the narrow-line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log nH (cm-2) < 21.
KW - Galaxies: active
KW - Galaxies: nuclei
KW - Galaxies: starburst
KW - Infrared: galaxies
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U2 - 10.1088/0004-637X/725/2/2270
DO - 10.1088/0004-637X/725/2/2270
M3 - Article
AN - SCOPUS:78650078063
VL - 725
SP - 2270
EP - 2280
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
ER -