The Spectral Energy Distribution and Emission‐Line Properties of the Narrow‐Line Seyfert 1 Galaxy Arakelian 564

We present the intrinsic spectral energy distribution (SED) of the NLS1Arakelian 564, constructed with contemporaneous data obtained during amulti-wavelength, multi-satellite observing campaign in 2000 and 2001. Wecompare it with that of the NLS1 Ton S180 and with those obtained for BLS1s toinfer how the relative accretion rates vary among the Sy1 population. Althoughthe peak of the SED is not well constrained, most of the energy is emitted inthe 10-100 eV regime, constituting roughly half of the emitted energy in theoptical/X-ray ranges. This is consistent with a primary spectral componentpeaking in the extreme UV/soft X-ray band, and disk-corona models, hence highaccretion rates. Indeed, we estimate that \dot{m}~1. We examine the emissionlines in its spectrum, and we constrain the physical properties of theline-emitting gas through photoionization modeling. The line-emitting gas ischaracterized by log n~11 and log U~0, and is stratified around log U~0. Ourestimate of the radius of the H\beta-emitting region ~10 \pm 2 lt-days isconsistent with the radius-luminosity relationships found for Sy1 galaxies. Wealso find evidence for super-solar metallicity in this NLS1. We show that theemission lines are not good diagnostics for the underlying SEDs and that theabsorption line studies offer a far more powerful tool to determine theionizing continuum of AGNs, especially if comparing the lower- andhigher-ionization lines.Comment: 15 pages, 10 figures; accepted for publication in The Astrophysical Journal, LaTeX emulateapj.st