Tracing the bright and dark sides of the universe with X-ray observations. Yasushi Suto. Department of Physics University of Tokyo

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1 Tracing the bright and dark sides of the universe with X-ray observations Yasushi Suto Department of Physics University of Tokyo 1

2 WMAP summary of cosmic energy budget baryons ordinary matter makes up merely 4 percent dark matter dark energy galaxies and clusters are surrounded by invisible mass an order-of-magnitude more massive than their visible part dominated by even more exotic component! homogeneously fills the universe (unclustered) repulsive force (negative pressure; P= ) Einstein s cosmological constant? 2

3 More intriguingly, most of the cosmic dark matter dark energy baryons baryon is also dark composition of cosmic baryons stars hot gas Cosmic Baryon Budget: Fukugita, Hogan & Peebles ApJ 503 (1998) 518 3

4 99% of the universe is DARK visible baryons 1% dark baryons 3% Quite frustrating We finally realized that we have not yet understood 99% of the universe at all! Beyond precision cosmology? from how much to what/where are they? 4

5 Can we understand the dark sides of the universe? Identify dark matter particles New physics beyond the standard model maybe new experimental results in next years important and feasible projects for experimental physicists, but no more for astronomical observations Identify dark energy (?) candidates Too challenging physics unlikely to have any major breakthroughs in this century Identify physical states of dark baryons Should be entirely in well-established established physics astronomical observations are essential 5

6 Dark and bright sides from cosmological SPH simulation SPH simulation in CDM : dark matter hot gas galaxy (Yoshikawa, Taruya, Jing & Suto 2001) 6

7 Large-scale structure in SPH simulation (75h -1 Mpc) 3 box z=0 N=128 3 :DM particles N=128 3 :gas particles (Yoshikawa et al. 2001) Galaxy (cold clump) Dark matter All gas particles Hot gas (T>10 7 K) Warm gas (10 5 K<T<10 7 K) 7

8 A filamentary region in SPH simulation (30h -1 Mpc) 3 box around a massive cluster at z=0 CDM SPH simulation Yoshikawa et al. 2001) Galaxy (cold clump) Dark matter All gas particles Hot gas (T>10 7 K) Warm gas (10 5 K<T<10 7 K) 8

9 Four phases of cosmic baryons Dave et al. ApJ 552(2001) 473 Condensed: >1000, T<10 5 K Stars + cold intergalactic gas Diffuse: <1000, T<10 5 K Photo-ionized intergalactic medium Ly absorption line systems Hot: T>10 7 K X-ray emitting hot intra-cluster gas Warm-hot: 10 5 K<T<10 7 K Warm-hot intergalactic medium ( (WHIM) Cen & Ostriker (1999) 9

10 Emission lines of oxygen in WHIM OVII (561eV, 568eV, 574eV, 665eV), OVIII (653eV) Why oxygen emission lines? Most abundant other than H and He Good tracers of gas around T= K No other prominent lines in E= eV Not restricted to regions towards background QSOs systematic WHIM survey 10

11 DIOS: Diffuse Intergalactic Oxygen Surveyor A Japanese proposal of a dedicated X-ray mission to search for dark baryons PI: Takaya Ohashi (Tokyo Metropolitan Univ.) + Univ. of Tokyo, JAXA/ISAS, Nagoya Univ., Tokyo Metro. Univ. A dedicated small satellite with cost < 40M USD. Proposed launch in 2008/2009 (not yet approved). Unprecedented energy spectral resolution: E=2eV in soft X-ray band (0.1-1keV) Aim at detection of 30 percent of the total cosmic baryons via Oxygen emission lines. 11

12 Requirements for detection Good energy resolution to identify the emission lines from WHIM at different redshifts E<5eV X-ray calorimeter using superconducting TES (Transition Edge Sensor) Large field-of of-view and effective area for survey S eff = 100cm 2, Ω=1deg 2 4-stage reflection telescope Angular resolution is not so important (but useful in removing point source contaminations) θ 600 h Mpc D 10 h 1 o 1 1 L Mpc 12

13 DIOS: instrument summary Area Field of View S Ω Angular Resol. Energy Resol. Energy Range Life > 100 cm 2 50' diameter ~100 cm 2 deg 2 3' (16 2 pixels) 2 ev (FWHM) kev > 5 yr Mechanical coolers + ADR: < 100 mk Initial cooling ~ 3 months 13

14 Expected S/N for OVIII line For a detector of S eff Ω =100cm 2 deg 2 and E=2eV T exp =10 5 sec T exp =10 4 sec T exp =10 6 sec 14

15 Searching for dark baryons with DIOS (Diffuse Intergalactic Oxygen Surveyor) PASJ 55 (2003) 879 astro-ph/ , Mock simulations Univ of Tokyo: K. Yoshikawa Y.Suto JAXA/ISAS: N. Yamasaki K. Mitsuda Tokyo Metropolitan Univ.: T. Ohashi Nagoya Univ.: Y. Tawara A. Furuzawa 15

16 Light-cone output from simulation z=0 z=0.3 Cosmological SPH simulation in Ω m =0.3, Ω Λ =0.7, σ 8 =1.0, and h=0.7 CDM with N=128 3 each for DM and gas (Yoshikawa, Taruya, Jing,, & Suto 2001) Light-cone output from z=0.3 to z=0 by stacking 11 simulation cubes of (75h -1 Mpc) 3 at different z 5 FOV mock data in 64x64 grids on the sky 128 bins along the redshift direction ( z=0.3/128)( 16

17 Surface brightness on the sky Bolometric X-ray emission 0.0< z < < z < < z < 0.11 OVII and OVIII line emission 0.0< z < < z < < z <

18 Metallicity models Oxygen enrichment scenario in IGM Type-II SNe galaxy wind merging metal pollution in IGM Metallicity of WHIM is quite uncertain Adopted models for metallicity distribution Model I : uniform and constant Z = 0.2 Z solar Model II : uniform and evolving Z = 0.2 Z solar (t/t 0 ) Model III : density-dependent (Aguirre et al. 2001) Z = Z solar (ρ/ρ mean ) 0.33 Model IV Z = 0.02 Z solar (ρ/ρ mean ) 0.3 (galactic wind driven) IV : density-dependent (Aguirre et al. 2001) (radiation pressure driven) 18

19 Creating Mock spectra from light-cone simulation output T=10 7 K T= K T=10 6 K For a given exposure time, convolve the emissivity according to gas density and temperature in (5 /64) 2 pixels over the lightcone Add the Galactic line emission (McCammon et al. 2002) Add the cosmic X-ray X background contribution (power-law+poisson noise) Then statistically subtract the Galactic emission and the CXB and obtain the residual spectra for E=2eV resolution. 19

20 Simulated spectra: region A Shallow survey observation with the DIOS field-of-view (16 2 pixels) A = 0.88 deg 2 T exposure = 3x10 5 sec 20

21 Simulated spectra: region D Deeper observation of targeted fields with DIOS (5 2 pixels) 19 x19 = deg 2 D T exposure =10 6 sec 21

22 Simulating the local universe Simulation by Dolag et al. (astro-ph/ ) Initial condition: smoothing the observed galaxy density field of IRAS 1.2 Jy galaxy survey (over 5h -1 Mpc), linearly evolving back to z=50 adiabatic run of dark matter and baryons (without cooling or feedback) in a canonical ΛCDM model Locating the WHIM in the local universe Yoshikawa, Dolag, Suto, Sasaki, Yamasaki, Ohashi, Mitsuda, Tawara, Fujimoto, Furusho, Furuzawa, Ishida & Ishisaki (2004), PASJ, submitted (astro-ph/ ) Independent and earlier work to consider oxygen emissions from WHIM in constrained simulations Kravtsov, Klypin & Hoffman, ApJ 571(2002)563 22

23 Simulated local universe vs. 2MASS map Hydra-Centaurus Coma Pisces-Perseus A3627 Virgo Horologium Soft X-ray map of the simulated local universe (Yoshikawa et al. 2004) 23

24 Tour of the simulated local universe Klaus Dolag (2003) 24

25 Simulated gas distribution on the supergalactic plane gas temperature Coma Hydra Centaurus Virgo A3627 Pisces-Perseus gas density (adopted) metallicity 25

26 Mock observation of simulated Coma S(0.5-2keV) T gas S(OVII) S(OVIII) 1 1 FOV 26

27 a small clump in front of simulated Coma S(0.5-2keV) T gas 10 ( 5h-1 Mpc) away from los toward Coma S(OVII) S(OVIII) 1 1 FOV 27

28 Soft X-ray X excess of Coma XMM-Newton observations of the outskirts of Coma (Finoguenov, Briel & Henry 2003, A&A 410, 777) X-ray filament of 0.2keV warm gas? Finoguenov et al. (2003) Simulated observation T=0.2keV) (1/8) (1/8) FOV 28

29 Fraction of cosmic baryons detectable via oxygen emission OVII OVIII DIOS detection limit (T exp =10 5 s; S/N=10) DIOS detection limit (T exp =10 5 s; S/N=10) 29

30 Locating Warm-Hot Intergalactic Medium via Oxygen emission lines Mock spectral observations of oxygen emission lines (Yoshikawa et al. 2003, 2004) DIOS will be able to locate 30 percent of the total cosmic baryons directly E=2eV, S eff Ω=100 [cm 2 deg 2 ], T exp =10 5 s, S/N=10 flux limit = 6x10-11 [erg/s/cm 2 /str] Things remain to be checked Validity of the collisional ionization equilibrium? Strategy to quantify the fraction of WHIM; targeted observations vs. blank survey Sciences with DIOS other than WHIM search 30

31 Thanks! 31