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Spectral Energy Distributions for AGN: New Perspectives from the Archives

Ranjan Vasudevan, IoA, Cambridge

Determining the broad-band emission from accreting supermassive black holes (SMBHs) in active galactic nuclei (AGN) is crucial for understanding the physical mechanisms at work in them. The optical-to-X-ray luminosity constitutes the bulk of the accretion luminosity from AGN, but the far-UV disc emission in particular has historically been hard to constrain.

We present optical-to-X-ray spectral energy distributions (SEDs) for a sample of 54 AGN observed with the Far Ultraviolet Spectroscopic Explorer (FUSE). We find that the hard X-ray bolometric corrections show significant scatter plotted against luminosity. However, we find evidence for increasing bolometric correction with Eddington ratio, indicating possible parallels with Galactic Black Hole (GBH) systems in which the SED shape undergoes similar changes between accretion states. We also present new simultaneous SEDs for the reverberation mapped sample of AGN using the XMM-EPIC pn and Optical Monitor archives.

The effect of radiation pressure from the nucleus is enhanced when dusty absorbing gas is present. The average AGN SEDs from this work can be used to derive an effective Eddington limit for dusty gas. Our comparison of this model with available data for three samples of AGN (local, Chandra Deep Field-South, Lockman Hole) suggests that long-lived absorption exists primarily in sub-effective Eddington ratio sources.