Locating missing baryons from oxygen emission lines with DIOS

Transcription

1 Locating missing baryons from oxygen emission lines with DIOS (Diffuse Intergalactic Oxygen Surveyor) Yasushi Suto Department of Physics University of Tokyo July 19, 2004 University College London WHIM and DIOS 1

2 WMAP: Wilkinson Microwave Anisotropy Probe NASA/WMAP Science team WHIM and DIOS 2

3 13.7Gyr 0.2Gyr CMB: Cosmic Microwave Background time 0.38Myr 3min sec relic thermal photons from the ancient universe the present reionization CMB photons recombination Big-bang history large-scale structure galaxy cluster galaxy formation first objects light element synthesis generation of quantum fluctuations Recombination of protons and electrons = decoupling of baryons and photons WHIM and DIOS 3

4 ancient document in cipher CMB all-sky map a cipher key spherical harmonics δt θ, ϕ ) T ( = a lm Y lm ( θ, ϕ ) l, m deciphered data temperature spectrum C = grammar to understand the universe cold dark matter model imprinted information age, geometry, and composition of the universe l a lm a * lm WHIM and DIOS 4

5 Angular power spectrum of CMB temperature fluctuations observed by WMAP baryon density Ω b spectral index of primordial fluctuations n s δt T ( θ, ϕ ) = a Y lm lm( θ, ϕ ) C = l matter density Ω 0 l, m a lm a * lm Spergel et al. ApJS 148(2003)175 curvature of the universe Ω Κ = Ω m +Ω WHIM and DIOS -1 5

6 age of the universe: 13.7 Gyr universe is spatially flat universe reionized at 0.2Gyr after Big-bang cosmic matter is dominated by dark matter cosmic energy is dominated by dark energy WHIM and DIOS 6

7 Results: weighing the universe baryons ordinary matter makes up merely 4 percent of the entire mass of the universe dark matter dark energy galaxies and clusters are surrounded by invisible mass an order-of-magnitude more massive than their visible part unknown elementary particles? universe is dominated by even more exotic component! homogeneously fills the universe (unclustered) repulsive force (negative pressure; equation of state:p= ) Einstein s cosmological constant? WHIM and DIOS 7

8 More intriguingly, most of the cosmic baryon dark matter dark energy is also dark baryons composition of cosmic baryons stars hot gas Cosmic Baryon Budget: Fukugita, Hogan & Peebles ApJ 503 (1998) 518 WHIM and DIOS 8

9 99% of the universe is DARK Quite frustrating We finally realized that we have not yet understood 99% of the universe at all! (dark baryons 3%) cosmological observations in the 20 th century have identified previously unknown hierarchy of matter beyond the standard model of particle physics one needs to understand the meaning of cosmological parameters beyond mere precise estimates of their values from how much to why WHIM and DIOS 9

10 hydrodynamical simulation with gas (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) WHIM and DIOS 10

11 Four phases of cosmic baryons 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 Dave et al. ApJ 552(2001) 473 Warm-hot intergalactic medium ( (WHIM) WHIM and DIOS 11

12 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 WHIM and DIOS 12

13 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 (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. WHIM and DIOS 13

14 Searching for dark baryons with DIOS (Diffuse Intergalactic Oxygen Surveyor) Mock simulations PASJ 55 (2003) 879 astro-ph/ , Univ of Tokyo: K. Yoshikawa Y.Suto JAXA/ISAS: N. Yamasaki K. Mitsuda Tokyo Metropolitan Univ.: T. Ohashi Nagoya Univ.: Y. Tawara A. Furuzawa WHIM and DIOS 14

15 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)( WHIM and DIOS 15

16 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 < 0.11 WHIM and DIOS 16

17 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) WHIM and DIOS 17

18 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. WHIM and DIOS 18

19 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 WHIM and DIOS 19

20 Simulated spectra: region D Deeper observation of targeted fields with DIOS (5 2 pixels) 19 x19 = deg 2 D T exposure =10 6 sec WHIM and DIOS 20

21 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 WHIM and DIOS 21

22 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) WHIM and DIOS 22

23 Tour of the simulated local universe Klaus Dolag (2003) WHIM and DIOS 23

24 Simulated gas distribution on the supergalactic plane gas temperature Coma Hydra Centaurus Virgo A3627 Pisces-Perseus gas density WHIM and DIOS 24 (adopted) metallicity

25 Mock observation of X-ray X filament extending around simulated A3627 S(0.5-2keV) T gas S(OVII) S(OVIII) 1 1 FOV WHIM and DIOS 25

26 Mock observation of simulated Coma S(0.5-2keV) T gas S(OVII) S(OVIII) 1 1 FOV WHIM and DIOS 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 WHIM and DIOS 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 WHIM and DIOS 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) WHIM and DIOS 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 WHIM and DIOS 30

31 Oxygen emission in supergalactic coordinates soft X-ray OVII OVIII WHIM and DIOS 31

32 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 WHIM and DIOS 32

33 Oxygen lines OVIIVII 1s 2 1s2s ( 3 S 1 ) 561eV 22.1 OVIIVII 1s 2 1s2p ( 3 P 1 ) 568eV 21.8 OVIIVII 1s 2 1s2p ( 1 P 1 ) 574eV 21.6 OVIIIVIII 1s 2p (Ly ) 653eV 19.0 OVIIVII 1s 2 1s3p 665eV 18.6 OVIIIVIII 1s 3p (Ly ) 775eV 16.0 NeIX 1s 2 1s2s ( 3 S 1 ) 905eV 13.7 NeIX 1s 2 1s2p ( 3 P 1 ) 914eV 13.6 NeIX 1s 2 1s2p ( 1 P 1 ) 921eV 13.5 WHIM and DIOS 33

34 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 WHIM and DIOS 34

35 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 WHIM and DIOS 35

36 DIOS: spacecraft Weight Size Attitude Power Total Payload Launch In orbit Control Accuracy Total Payload ~ 400 kg ~ 280 kg m m 3-axis bias momentum wheel, Sun pointing in 1 axis 10 arcsec 450 W 250 W Altitude: ~ 550 km Inclination: 30 Rotation period: 95 min 1.5 m 5.9 m WHIM and DIOS 36

37 DIOS: comparison with other missions Very high sensitivity (SΩ and E) in detecting oxygen emission lines Intensity ratios of the lines reveal the temperature and ionization condition of WHIM WHIM and DIOS 37

38 Physical properties of the probed baryons Each symbol indicate the temperature and the over-density of gas at each simulation grid (4x4 smoothed pixels over the sky and z=0.3/128) S x > 3x10-10 [erg/s/cm 2 /sr] S x > 6x10-11 [erg/s/cm 2 /sr] S x > [erg/s/cm 2 /sr] WHIM and DIOS 38

39 Dependence on the metallicity model We have adopted model I (constant 0.2 solar metallicity) so far Density-dependent metallicity models show stronger emission lines. WHIM will be unambiguously detected with our proposed mission WHIM and DIOS 39