1. Taotao Fang UC Berkeley Collaborator: R. Croft, W. Sanders, J. Houck, R. Dave, N, Katz, D. Weinberg, L. Hernquist Soft X-ray Emission from the Warm-Hot Intergalactic Medium

2. Baryon Phase Diagram: Dave et al. (2001), Croft et al. (2001)

3. Cosmic X-ray Background Total Cosmic X-ray background (0.5 - 2 keV): ~ 6. - 8. 10 -12 ergs cm -2 s -1 deg -2 Contribution from discrete sources: 74 - 94 % (Mushotzky et al. 2000) Contribution from WHIM: likely ~ 5% (simulations from Croft et al. 2000, Phillips et al. 2001) Metal line emission account for a significant portion of WHIM emission!

4. Simulating X-ray emission Parallel TreeSPH simulation by Dave, Katz, Weinberg & Hernquist (see Dave et al. 2001, Croft et al. 2001 for details). CDM with a cosmological constant –   = 0.6,  m = 0.4 –  b = 0.02 h -2 The simulation volume: a cube of side-length 50 h -1 Mpc The spatial resolution is 7 h -1 kpc Density-depended metallicity

7. Enlarged Region of Area (A) and (B): (A)(B)

8. Cross-correlation of metal emission with nearby galaxies

9. Auto-correlation:

10. In Partnership With: M ISSING B ARYON E XPLORER A mission to locate baryons… …on the road to completing our picture of the Universe Missing Baryon Explorer Energy Range40 – 2000 eV Energy Resolution4 eV (FHWM) Angular Resolution4.9 arcmin Field of View29.5’ x 29.5’ FeaturesSelected deep pointings All-sky survey Guest observer program

11. Configuration and Detection Limits InstrumentAstro-E2Constellation-XXEUSMBE A (cm 2 )353,00040,000200 Ω FOV 2.9’x2.9’2.5’x 2.5’1x129.5x29.5 Ω PIXEL 0.48’ x 0.48’5’x5’2”x2”4.9x4.9 R100400500150 RAΩ FOV (cm 2 deg 2 ) 72,0835,5566439 EW (ev)138.08.04.94.5

12. MBE view of a 10º x 10º sky region

14. MBE sky coverage: This plot shows the fraction of the sky probed by MBE with at least one detectable emission line.

15. Summary Cosmological simulations: quantitative predictions of the physical properties of the WHIM gas and its observational signatures. X-ray emission: mapping 3-D distribution of the WHIM gas. By combining imaging/spectroscopy measurement, X-ray emission shall provide direct evidence of the WHIM gas. Cross-correlation with nearby galaxies: X-ray emission lines show strong cross-correlation with nearby large scale structure. Angular correlation: WHIM gas tends to cluster strongly at small angle. Future prospective: high spatial/spectral resolution X-ray telescopes.