Theme 1: Census of cosmic baryons
Surveys at various wavelengths have provided inventories of cosmic baryons in different phases. Most relevant to the meeting is those in the warm and hot phases that are believed to be associated with the cosmic web or circumgalactic medium. The topics may include:
1. Baryon census based on UV absorption line studies
2. Baryon census based on X-ray absorption line studies
3. Baryon census based on X-ray emission line studies
4. Baryon census based on other methods
Theme 2: Baryons in the intergalactic medium
The question of “missing baryons” is of interest here, both in theoretical and observational contexts. More importantly, what are the physical and chemical properties of IGM gas? The topics may include:
1. Results from hydrodynamic simulations
2. Observations of the warm-hot intergalactic medium
3. Heating and chemical enrichment of the intergalactic medium
4. Prospects for imaging the cosmic web
Theme 3: Baryons in the circumgalactic medium
Reservoirs of warm-hot baryons may exist in the vicinity of galaxies. The properties of CGM/halo gas are thought to be strongly influenced by stellar and AGN feedback processes that are not entirely understood. Observations have provided important clues. The topics may include:
1. Results from hydrodynamic simulations
2. Observations of the warm-hot circumgalactic medium
3. Heating and chemical enrichment of the circumgalactic medium
4. Baryon content of galaxies
5. X-ray/UV spectroscopic studies of galactic halos
6. Studies of galactic halos through SZ effects
Theme 4: Soft diffuse X-ray background
The origin of the diffuse X-ray background at below 1 keV is still an unresolved issue. Contributions from the “Local Bubble” and halo gas in the Milky Way have been studied extensively. Contamination by the solar wind charge exchange is thought to be important but has been difficult to quantify. Progress has been made in recent years, both theoretically and observationally. The topics may include:
1. Contribution from the Local Bubble
2. Contribution from the Galactic halo
3. Contribution from solar wind charge exchange
4. Spectroscopic characteristics of the components
5. Theories of the soft diffuse X-ray background
Theme 5: Prospects for dedicated high-resolution spectroscopic missions at X-ray wavelengths
To enable significant progress on the scientific issues outline above, improved spectroscopic (and imaging) capabilities are clearly needed at soft X-ray wavelengths. Future missions and several mission concepts will be presented in this context.