T. Ohashi (Tokyo Metropolitan University) IXO and WHIM T. Ohashi (Tokyo Metropolitan University) Science of WHIM Status of WHIM search (X-ray and UV) Suzaku results on LSS and cluster outskirts Expectation with IXO XGS Summary

Thermal history of the universe Big bang Light elements Recombination 1st stars Reionization Galaxies Clusters Large –scale structure Present Metal synthesis Shock heating Cooling by expansion 102 K 3m 0.38M 0.2G 0.8G 5G 13.7Gyr Age of the Universe 104 K Reionization by UV and X 106 K IGM temperature WHIM (warm-hot intergalactic medium) will tell us the evolution of the hot-phase material in the universe

Baryon phase Wide area in the baryon phase space is unexplored Branchini et al. 09 Oxygen line probes the dark baryon efficiently EDGE consortium Bregman 07

Cosmic structure Dark matter Galaxies (~104K) WHIM (105-107 K) traces the cosmic large-scale structure = “Missing baryon” Typical matter density: d (=n/nB) = 10 - 100 Yoshikawa et al. 2001, ApJ, 558, 520 size = 30 h-1 Mpc  5 deg at z=0.1 IGM (105-107K) Cluster gas (107K)

Sculptor Wall by Chandra and XMM Fang et al. 2010, ApJ 714, 1715 Scupltor wall (z = 0.03  0.002) via absorption of blazar H2356-309 (z = 0.165) XMM RGS (130 ks) + Chandra LETG (520 ks) combined OVII (21.6 A) absorption line detected at z = 0.03 with 4.0s significance (EW = 26 mA) If depth of L = 15 Mpc (filling the wall) and ZO = 0.1 solar assumed, overdensity becomes d  30 Consistent with WHIM filling the filament Chandra

FUSE and XMM detection of WHIM Nicastro et al. 2010, ApJ 715, 854 XMM RGS PKS0558-504 (z = 0.1372) shows OVIII (XMM) and HI Lyb (FUSE) absorption lines at z = 0.117 XMM RGS data with 900 ksec in total show 2.8s significance FUSE data show Lyb (4s) but no OVI feature  T > 3.3  106 K Metallicity 1% - 4% solar (absorption unlikely to be AGN outflow) and NH  1.5  1021 cm-2 Estimated T infers overdensity  300 and L  5 Mpc OVIII (z = 0.116) FUSE HI Lyb (z = 0.118)

COS detection of nearby WHIM Narayanan et al. 2010 ApJ, 721, 960 Broad Lya (COS) and OVI (FUSE) at z = 0.0103 against Mrk 290 (z = 0.0296) Line width: T = 1.4  105 K OVI is likely to be photoionized (combination of non-equilibrium coll. ion. and photoionization necessary) Large-scale filament (20) exists Possible connection with NGC5987, at about 400 kpc away from the absorption system

COS study of distant WHIM Narayanan et al. 2011 ApJ, 730, --- NeVIII and OVI (both with COS) absorption at z = 0.495 against PKS 0405-123 (z = 0.57) Line data: T  5  105 K, NH = 1019- 20 cm-2, ZNe  0.25 solar NeVIII probes collisionally ionized gas, while OVI is likely to be photoionized Hot halo of a galaxy or WHIM NeVIII useful in studying coll. ion. gas

Suzaku search for WHIM Suzaku is searching for WHIM in cluster outskirts and in superclusters, with no positive detection of redshifted O lines yet Suzaku is giving fairly low upper limits (d < 300 assuming line-of-sight depth of 2 Mpc and ZO = 0.1 solar) Suzaku will continue searching for WHIM in all possible locations

Cluster outskirts with Suzaku Rvir (2.7 Mpc) A2142 outskirt Akamatsu et al. 2011 in prep A1413 outskirt Rvir Hoshino et al. 2010 PASJ Significant X-ray emission detected out to Rvir Systematic errors due to fluctuation of CXB, Galactic background, non X-ray background, XIS filter contamination evaluated Effect of stray light from bright center less than 7% of the observed flux

Cluster outskirts with Suzaku "Uniform" temperature profile by Burns et al. 2010, ApJ 721, 1105 Akamatsu et al. 2011 in prep A2142 r1.1 K = kT/n2/3 Entropy drop at > 0.5 rvir is seen in several clusters Clumpiness explains only a few % drop Non equilibrium (Ti > Te) more likely? Nagai and Lau 2011 ApJL

Filament junction by Suzaku Search for (and detection of ) X-ray emission from large-scale junction of filaments Kawahara et al. 2011 ApJL 727, L38 DisPerSE : filament extractor Sousbie 2010, Sousbie, Pichon, & Kawahara 2010 RASS map with SDSS galaxies LOS

Suzaku J1552+2739: a group of galaxies X-ray intensity contour Hardness ratio map 1.64 keV "hot spot" 3.91 keV NXB subtracted & vignetting corrected image LX = 2.4  1043 erg/s Likely to be a group undergoing major merger Filament junction could host many undetected X-ray groups These should explain some of the missing baryons

IXO: grating spectrometer Big jump from Chandra and XMM-Newton grating spectrometers by factor of > 10 in effective area and 3 - 7 times higher resolution Sensitive to Equivalent Width  2 meV R = 3000 can resolve v = 100 km/s, such as structures of galactic winds l/Dl

IXO: absorption study OVII, OVIII absorptions: WHIM presence beyond any doubt Predicted dN/dz of OVII, OVIII clouds (normalized with OVI results): several absorption systems per AGN will be detected There are > 100 useful AGNs for absorption study (FX > 5  10-11 cgs), and observation of 30 AGNs will reveal 100 WHIM clouds IXO: 600 ksec OVII OVI OVIII 1 10 100 0.1 IXO dN/dz EW (mÅ) Bregman et al. IXO-WP

WHIM emission study Grasp of XMS: equally large as those of dedicated missions 5” angular resolution resolves 16 kpc at z = 0.2 (galactic outflow scale) Grasp /ORIGIN Simulated spectrum WHIM Galactic

WHIM search using resonance scatting Churazov et al. 2001, MN 323, 93 Churazov, 2010, Space Sci. Rev. 157, 193 WHIM can be surrounding bright AGNs or groups Part of continuum X-rays undergoes resonant scattering by WHIM gas For d ~ 30, a few Mpc region around bright AGNs will shine in OVII and/or OVIII lines Rough estimation shows that an AGN with LX = 1046 erg/s at z = 0.2 can produce about 100 OVII counts with IXO over ~ 5 arcmin region in 100 ksec observation Weaker or comparable to the thermal line intensity, but this is an additional emission scaling with n

Resonance scattering from WHIM AGN/group WHIM O line Mpc scale halo AGN (or gal. group) X-rays will be resonantly scattered by OVII and OVIII ions in surrounding WHIM A few Mpc scale extended halo of O lines is expected Radial profile is much flatter than thermal emission from group gas S. brightness OVII from group r-3 r-1 WHIM halo r

Summary WHIM will give us unique information about thermal and chemical evolution of the universe Absorption and emission studies with IXO will reveal all phases of warm-hot baryons within z  0.5 Absorption study with IXO will probe low-density WHIM clouds (d < 100) Emission measurement will also show us the spatial structure (filaments, outflows) of WHIM Resonance scattering may show oxygen-line halos with ~ Mpc scale around bright objects