Synthetic absorption lines for a clumpy medium: a spectral signature for cloud acceleration in AGN?
| Autor: | Randall Dannen, Tim Waters, Daniel Proga, Timothy R. Kallman |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
Active galactic nucleus Spectral signature Absorption spectroscopy 010308 nuclear & particles physics FOS: Physical sciences Astronomy and Astrophysics Photoionization Astrophysics Astrophysics - Astrophysics of Galaxies 01 natural sciences Spectral line Space and Planetary Science Ionization Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences Absorption (electromagnetic radiation) 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Line (formation) |
| DOI: | 10.48550/arxiv.1611.00407 |
| Popis: | There is increasing evidence that the highly ionized multiphase components of AGN disk winds may be due to thermal instability. The ions responsible for forming the observed X-ray absorption lines may only exist in relatively cold clumps that can be identified with the so-called 'warm absorbers'. Here we calculate synthetic absorption lines for such warm absorbers from first principles by combining 2D hydrodynamic solutions of a two-phase medium with a dense grid of photoionization models to determine the detailed ionization structure of the gas. Our calculations reveal that cloud disruption, which leads to a highly complicated velocity field (i.e. a clumpy flow), will only mildly affect line shapes and strengths when the cold gas becomes highly mixed but not depleted. Prior to complete disruption, clouds which are optically thin to the driving UV resonance lines will cause absorption at an increasingly blueshifted line of sight velocity as they are accelerated. This behavior will imprint an identifiable signature on the line profile if warm absorbers are enshrouded in an even broader absorption line produced by a high column of intercloud gas. Interestingly, we show that it is possible to develop a spectral diagnostic for cloud acceleration by differencing the absorption components of a doublet line, a result which can be qualitatively understood using a simple partial covering model. Our calculations also permit us to comment on the spectral differences between cloud disruption and ionization changes driven by flux variability. Notably, cloud disruption offers another possibility for explaining absorption line variability. Comment: 14 pages, 7 figures, to appear in MNRAS |
| Databáze: | OpenAIRE |
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