New Indicators for AGN Power: The Correlation between [O IV] 25.89 μm and Hard X-Ray Luminosity for Nearby Seyfert Galaxies
The Astrophysical Journal
Galaxies: seyfert, Infrared: galaxies, X-Rays: galaxies
We have studied the relationship between the [O IV] 25.89 μm emission-line luminosities, obtained from Spitzer spectra, the X-ray continua in the 2-10 keV band, primarily from ASCA, and the 14-195 keV band obtained with the SWIFT Burst Alert Telescope (BAT), for a sample of nearby (z < 0.08) Seyfert galaxies. For comparison, we have examined the relationship between the [O III] λ5007, the 2-10 keV, and the 14-195 keV luminosities for the same set of objects. We find that both the [O IV] and [O III] luminosities are well correlated with the BAT luminosities. When comparing [O IV] and [O III] luminosities for the different types of galaxies, we find that the Seyfert 2s have significantly lower [O III] to [O IV] ratios than the Seyfert 1s. We suggest that this is due to more reddening of the narrow-line region (NLR) of the Seyfert 2s, since the [O IV] 25.89 μm emission line is much less affected by extinction. The combined effects of reddening and the X-ray absorption is the probable reason why the [O III] versus 2-10 keV correlation is better than the [O IV] versus 2-10 kev correlation. Based on photoionization models, we find that the [O IV] comes from higher ionization states and lower density regions than previous studies had determined for [O III]. Overall, we find the [O IV] to be an accurate indicator of the power of the AGN.
Melendez, M., Kraemer, S. B., Armentrout, B. K., Deo, R. P., Crenshaw, D. M., Schmitt, H. R., Mushotzky, R. F., Tueller, J., Markwardt, C. B., & Winter, L. (2008). New Indicators for AGN Power: The Correlation between [O IV] 25.89 μm and Hard X-Ray Luminosity for Nearby Seyfert Galaxies. The Astrophysical Journal, 682, (1), 94 - 103. https://doi.org/10.1086/588807. Retrieved from https://nsuworks.nova.edu/cnso_chemphys_facarticles/157