Unveiling slim accretion disc in AGN through X-ray and Infrared observations

Abstract

In this work, which is a continuation of Castelló-Mor et al. (2016), we present new X-ray and infrared (IR) data for a sample of active galactic nuclei (AGN) covering a wide range in Eddington ratio over a small luminosity range. In particular, we rigorously explore the dependence of the optical-to-X-ray spectral index ${\alpha }_{OX}$ and the IR-to-optical spectral index on the dimensionless accretion rate, $\dot{\mathcal{M}}=\dot{m}/\eta$ where $\dot{m}=L_{AGN}/L_{Edd}$ and $\eta$ is the mass-to-radiation conversion efficiency, in low and high accretion rate sources. We find that the SED of the faster accreting sources are surprisingly similar to those from the comparison sample of sources with lower accretion rate. In particular: i) the optical-to-UV AGN SED of slow and fast accreting AGN can be fitted with thin AD models. ii) The value of ${\alpha }_{OX}$ is very similar in slow and fast accreting systems up to a dimensionless accretion rate ${\dot{\mathcal{M}}}_c\sim$10. We only find a correlation between ${\alpha }_{OX}$ and $\dot{\mathcal{M}}$ for sources with $\dot{\mathcal{M}}>{\dot{\mathcal{M}}}_c$. In such cases, the faster accreting sources appear to have systematically larger ${\alpha }_{OX}$ values. iii) We also find that the torus in the faster accreting systems seems to be less efficient in reprocessing the primary AGN radiation having lower IR-to-optical spectral slopes. These findings, failing to recover the predicted differences between the SEDs of slim and thin ADs within the observed spectral window, suggest that additional physical processes or very special geometry act to reduce the extreme UV radiation in fast accreting AGN. This may be related to photon trapping, strong winds, and perhaps other yet unknown physical processes.

Accepted for publication on MNRAS, 14 pages, 7 figures

References in corpus (4)

• A Global Three Dimensional Radiation Magneto-hydrodynamic Simulation of Super-Eddington Accretion Disks
• Simultaneous X-ray/optical/UV snapshots of active galactic nuclei from XMM-Newton: spectral energy distributions for the reverberation mapped sample
• The black hole mass - stellar velocity dispersion relation of narrow-line Seyfert 1 galaxies
• A comparison of hard X-ray photon indices and iron \ka emission lines in X-ray luminous narrow- and broad-line Seyfert 1 galaxies

Cited by in corpus (6)

• Accretion Disk Sizes from Continuum Reverberation Mapping of AGN Selected from the ZTF Survey
• The Extreme Super-Eddington NLS1 RX J0134.2-4258 -- II. A Weak-Line Seyfert Linking to the Weak-Line Quasar
• Connecting Low- and High-Redshift Weak Emission-Line Quasars via HST Spectroscopy of Ly$\alpha$ Emission
• The first X-ray look at SMSS J114447.77-430859.3: the most luminous quasar in the last 9 Gyr
• Radio Scrutiny of the X-ray-Weak Tail of Low-Mass Active Galactic Nuclei: A Novel Signature of High-Eddington Accretion?
• Slim accretion disks: theory and observational consequences