The O VI Distribution in the ISM - Predictions From Global MHD and HD Models and Comparison with Observations
- Author(s)
- Miguel A. de Avillez, Dieter Breitschwerdt
- Abstract
A crucial test for the present day models of the interstellar medium is the reproduction of the measured amount of Ovi in the ISM in general and in the Local Bubble in particular. We have calculated the Ovi absorption column densities (under the assumption of collisional ionization equilibrium) in the ISM and Local Bubble (embedded in an inhomogeneous ISM) by means of 3D adaptive mesh refinement HD and MHD simulations on large (10 kpc) and small (0.625 pc) scales over a sufficiently large timescale (400 Myrs) in order to establish a global dynamical equilibrium and wipe out the imprint of the initial conditions. The Ovi distribution is monitored through lines of sight measurements at different locations, one inside of the Local Bubble, while the other ISM locations were chosen at random. We obtain a correlation between N(Ovi) and distance, which is independent of the observer's vantage point in the disk. In particular, the location of the observer inside a hot bubble does not have any influence on the correlation, because the contribution of an individual bubble (with a typical extension of 100 pc) is negligibly small. The general ISM and Local Bubble runs show an Ovi distribution in agreement with Copernicus and recent FUSE results. In particular, there is a remarkable agreement between observations and the simulated N(Ovi) as a function of distance, the averaged Ovi density ( 1.8× 10-8 cm-3), the constancy of the N(Ovi) dispersion with distance, and the N(Ovi) in the LB being <8× 1012 cm-2. Overall our results strongly support the important role of turbulent mixing in the distribution of Ovi clumps in the ISM. Supernova induced turbulence is quite strong and unavoidable due to shearing motions in the ISM and operates on a large range of scales.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Universidade de Évora
- Journal
- Bulletin of the American Astronomical Society
- Volume
- 38
- Pages
- 110
- ISSN
- 0002-7537
- Publication date
- 2006
- Austrian Fields of Science 2012
- 103004 Astrophysics, 103003 Astronomy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/d5b6cda1-0007-4506-a24a-316a80c61a2f