NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-24 T19:19:11 PDT
Help | Comment | NED Home

For refcode 2010ApJS..187...64G:
Retrieve 92 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2010ApJS..187...64G The Simultaneous Optical-to-X-Ray Spectral Energy Distribution of Soft X-Ray Selected Active Galactic Nuclei Observed by Swift Grupe, Dirk; Komossa, Stefanie; Leighly, Karen M.; Page, Kim L. Abstract. We report Swift observations of a sample of 92 bright soft X-ray selected active galactic nuclei (AGNs). This sample represents the largest number of AGNs observed to study the spectral energy distribution (SED) of AGNs with simultaneous optical/UV and X-ray data. The principal motivation of this study is to understand the SEDs of AGNs in the optical/UV to X-ray regime and to provide bolometric corrections which are important in determining the Eddington ratio L/L_Edd_. In particular, we rigorously explore the dependence of the UV-EUV contribution to the bolometric correction on the assumed EUV spectral shape. We find strong correlations of the spectral slopes {alpha}_X_ and {alpha}_UV_ with L/L_Edd_. Although narrow-line Seyfert 1 galaxies (NLS1s) have steeper {alpha}_X_ and higher L/L_Edd_ than broad-line Seyfert 1 galaxies (BLS1s), their optical/UV to X-ray spectral slopes {alpha}_ox_ and optical/UV slopes {alpha}_UV_ are very similar. The mean SED of NLS1s shows that in general this type of AGNs appears to be fainter in the UV and at hard X-ray energies than BLS1s. We find a strong correlation between {alpha}_X_ and {alpha}_UV_ for AGNs with X-ray spectral slopes {alpha}_X_<1.6. For AGNs with steeper X-ray spectra, both this relation and the relation between {alpha}_X_ and L/L_Edd_ break down. At {alpha}_X_~1.6, L/L_Edd_ reaches unity. We note an offset in the {alpha}_UV_-L/L_Edd_ relation between NLS1s and BLS1s. We argue that {alpha}_UV_ is a good estimator of L/L_Edd_ and suggest that {alpha}_UV_ can be used to estimate L/L_Edd_ in high-redshift QSOs. Although NLS1s appear to be highly variable in X-rays, they only vary marginally in the UV. Key words: galaxies: active
Retrieve 92 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home