Where Are the Baryons? II. Feedback Effects
Abstract
Numerical simulations of the intergalactic medium have shown that at the present epoch, a significant fraction (40%-50%) of the baryonic component should be found in the (T~106 K) warm-hot intergalactic medium (WHIM)-with several recent observational lines of evidence indicating the validity of the prediction. We here recompute the evolution of the WHIM with the following major improvements: (1) galactic superwind feedback processes from galaxy and star formation are explicitly included; (2) major metal species (O V to O IX) are computed explicitly in a nonequilibrium way; and (3) mass and spatial dynamic ranges are larger by factors of 8 and 2, respectively, than in our previous simulations. Here are the major findings: (1) Galactic superwinds have dramatic effects, increasing the WHIM mass fraction by about 20%, primarily through heating of warm gas near galaxies with density 101.5-104 times the mean density. (2) The fraction of baryons in the WHIM is increased modestly from the earlier work but is still ~40%-50%. (3) The gas density of the WHIM is broadly peaked at a density 10-20 times the mean density, ranging from underdense regions to regions that are overdense by 103-104. (4) The median metallicity of the WHIM is 0.18 Zsolar for oxygen, with 50% and 90% intervals being (0.040,0.38) and (0.0017,0.83).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2006
- DOI:
- 10.1086/506505
- arXiv:
- arXiv:astro-ph/0601008
- Bibcode:
- 2006ApJ...650..560C
- Keywords:
-
- Cosmology: Observations;
- Galaxies: Intergalactic Medium;
- Cosmology: Large-Scale Structure of Universe;
- Astrophysics
- E-Print:
- 44 pages, 17 figures, high res version at http://www.astro.princeton.edu/~cen/baryonII.ps.gz