| |
 |
| Paper: |
The He II Lyman alpha Forest: Evaluation of Simulated Data |
| Volume: |
348, Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE |
| Page: |
360 |
| Authors: |
Fechner, C.; Reimers, D. |
| Abstract: |
Using an artificial H I Lyα spectrum we simulate the corresponding He II forest with fixed values of η and a Doppler parameter consisting of a thermal and a turbulent part. In addition metal lines with line strengths and line density as expected in the case of HS 1700+6416 are superimposed. FUSE–like noise is added. The analysis of the simulated spectra in terms of Doppler profiles recovers the input η = N(He II)/N(H I) with a scatter by a factor of 10. About 10% have significantly lower η-values for various reasons. The majority of the extremely high η-values (up to 1000) are evidently caused by metal lines. We conclude that part of the scatter in η of previous analyses of the He II forest in HE 2347-4342 can be regarded as an artifact. However, we confirm that the correlation between small column densities (in voids) and high η-values is not a methodical artifact and appears to be a true phenomenon. |
|
|
|
|
|
