The spectral energy distribution of PKS 2004-447: a compact steep-spectrum source and possible radio-loud narrow-line Seyfert 1 galaxy
| Autor: | Jun Kataoka, E. Ferrero, J. G. Greenhill, Matthew Whiting, W. Brinkmann, Simon Ellingsen, Z. Misanovic, Luigi C. Gallo, Th. Boller, Alicia Oshlack, Philip G. Edwards, William F. Welsh, D. R. Lewis |
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| Jazyk: | angličtina |
| Rok vydání: | 2006 |
| Předmět: |
Physics
Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Near-infrared spectroscopy FOS: Physical sciences Flux Astronomy and Astrophysics Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Synchrotron Galaxy law.invention Luminosity Wavelength Space and Planetary Science law Spectral energy distribution Astrophysics::Galaxy Astrophysics Line (formation) |
| Popis: | (abridged) The spectral energy distribution (SED) of the compact steep spectrum (CSS) source and possible radio-loud narrow-line Seyfert 1 galaxy (NLS1), PKS2004-447, is presented. Five out of six well studied RL NLS1 share this dual classification (optically defined as a NLS1 with radio definition of a CSS or giga-hertz peaked spectrum (GPS) source). The SED is created from simultaneous observations at radio (ATCA), optical/NIR (Siding Spring) and UV/X-ray (XMM-Newton) wavelengths. The X-ray data show evidence of short-term variability, a possible soft excess, and negligible absorption. Together with the rest of the SED, the X-ray emission is excessive in comparison to synchrotron plus synchrotron self-Compton (SSC) models. The SED can be described with a two component model consisting of extended synchrotron/SSC emission with Comptonisation in the X-rays, though SSC models with a very high electron-to-magnetic energy density ratio cannot be excluded either. The peak emission in the SED appears to be in the near infrared, which can be attributed to thermal emission from a dusty torus. Analysis of a non-contemporaneous, low resolution optical spectrum suggests that the narrow-line region (NLR) is much more reddened than the X-ray emitting region suggesting that the gas-to-dust ratio in PKS2004-447 may be very different then in our own Galaxy. Long-term radio monitoring of PKS2004-447 shows a rather constant light curve over nearly a six month period with the exception of one outburst when the 6.65GHz flux increased by ~35% over 19 days. In comparison to general samples of GPS sources, which appear to be X-ray weak, NLS1-CSS/GPS sources possess stronger X-ray emission relative to radio, and lower intrinsic absorption than GPS sources of similar X-ray luminosity. 10 pages, 8 figures. Accepted for publication in MNRAS |
| Databáze: | OpenAIRE |
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