科研之友
微信
新浪微博
Facebook
分享链接
摘要
The shape of the spectral energy distribution (SED) of active galaxies in the extreme-ultraviolet (EUV)-soft X-ray band (13.6 eV-1 keV) is uncertain because obscuration by dust and gas can hamper our view of the continuum. To investigate the shape of the SED in this energy band, we have generated a set of photoionization models which reproduce the small dispersion found in correlations between high-ionization mid-infrared emission lines in a sample of hard X-ray-selected active galactic nuclei (AGNs). Our calculations show that a broken power-law continuum model is sufficient to reproduce the [Ne v](14.32) mu m/[Ne III], [Ne v](24.32) mu m/[O IV](25.89) mu m, and [O IV](25.89) mu m/[Ne III] ratios and does not require the addition of a "big bump" EUV model component. We constrain the EUV-soft X-ray slope, alpha(i), to be between 1.5 and 2.0 and derive a best fit of alpha(i) similar to 1.9 for Seyfert 1 galaxies, consistent with previous studies of intermediate-redshift quasars. If we assume a blue bump model, most sources in our sample have derived temperatures between T-BB = 10(5.18) K and 10(5.7) K, suggesting that the peak of this component spans a large range of energies extending from similar to 600 angstrom to 1900 angstrom. In this case, the best-fitting peak energy that matches the mid-infrared line ratios of Seyfert 1 galaxies occurs between similar to 700 and 1000 angstrom. Despite the fact that our results do not rule out the presence of an EUV bump, we conclude that our power-law model produces enough photons with energies >4 Ry to generate the observed amount of mid-infrared emission in our sample of Burst Alert Telescope AGNs.
- 出版日期2011-9-1
