1. Ringberg workshop May 3-5 2004/ Noriko Yamasaki1 Detectability of warm intergalactic medium and the DIOS mission Noriko Yamasaki ISAS/JAXA

2. Ringberg workshop May 3-5 2004/ Noriko Yamasaki2 “Cosmic Baryon Budget” requires missing baryon The observed baryons are only 10-40% of the expected valued from big-bang nucleosynthesis. The observed baryons are only 10-40% of the expected valued from big-bang nucleosynthesis.  star +  HI +  H2 +  hot X-ray = 0.0068 +0.0041 -0.0030 vs  BBN =0.04 (Fukugita, Hogan, & Peebles 1998) The other phase of cosmological baryons? The other phase of cosmological baryons? Star: Condensed T 1000 Lyman alpha forest: Diffuse T<10 5 K,  <1000 X-ray:hot ICM T>10 7 K Is there other phase of baryon ?

3. Ringberg workshop May 3-5 2004/ Noriko Yamasaki3 Where are missing baryons in the Universe ? volume fraction mass fraction hot gas cold gas warm-hot gas hot gas cold gas galaxy warm-hot gas ~40% of total baryons at z=0 are IGM with 10 5 K<T<10 7 K (Cen & Ostriker 1999)

4. Ringberg workshop May 3-5 2004/ Noriko Yamasaki4 A close-up view of a filament Galaxies (cold clump) Dark matterWarm gas (10 5 K<T<10 7 K) Hot gas (T>10 7 K) All gas particles A 30 Mpc/h box around a massive cluster at z=0 Warm gas follow dark matter very well.  CDM simulation by Yoshikawa et al. 2002)

5. Ringberg workshop May 3-5 2004/ Noriko Yamasaki5 How can we observe the WHIM ? 1. OVI,OVII, & OVIII absorption lines ? 2. Bumpy soft X-ray background ? Some published trials and our new results around Virgo cluster 3. OVII and OVIII emission lines with good energy resolution ? Difficult for a large X-ray observatory, so we need a new approach

6. Ringberg workshop May 3-5 2004/ Noriko Yamasaki6 Absorption lines in QSO spectra OVII, OVIII absorption lines at z=0/Local group ? PKS2155-304, 3C273, Mrk 421, 3C120 (Rasmussen et al. 2003) OVII, OVIII absorption lines at z=0/Local group ? PKS2155-304, 3C273, Mrk 421, 3C120 (Rasmussen et al. 2003) ISM toward a LMXB also make an absorption line. (4U1820-303 in Futamoto et al. 2004) ISM toward a LMXB also make an absorption line. (4U1820-303 in Futamoto et al. 2004)

7. Ringberg workshop May 3-5 2004/ Noriko Yamasaki7 Soft X-Ray excess around a cluster ? From the outer region of Coma cluster, soft emission with kT~0.2 keV and abundance of 0.1 is found. Looks stronger than Galactic emission, which has large uncertainty in modeling. (Finoguenov et al. 2003)

8. Ringberg workshop May 3-5 2004/ Noriko Yamasaki8 Detection of OVIII absorption lines associated with Virgo cluster Virgo cluster: nearby and very elongated Virgo cluster: nearby and very elongated LBQS 1228+1116 (z=0.237) 83 arcmin away from M87 LBQS 1228+1116 (z=0.237) 83 arcmin away from M87 54 ksec exposure with XMM- Newton 54 ksec exposure with XMM- Newton (Fujimoto et al. in preparation)

9. Ringberg workshop May 3-5 2004/ Noriko Yamasaki9 Marginal detection of red-shifted line O VIII O VII Energy (eV) 650.9 (+0.8 -1.9) 571.6 (fixed) Cz (km/s) 1253 (+881-369) -- EW (eV) 2.8 (+1.3 -2.0) <2.8 (3  ) N ion (/cm 2 ) 6.2(+3.3 -4.4)x 10 16 <3.7 x10 16 (3  ) Best fit 19.05 Rest frame 18.97 2.3  detection with maximum likelihood method. cz is consistent with that of M87, 1307 km/s kT>0.20 keV

10. Ringberg workshop May 3-5 2004/ Noriko Yamasaki10 Search the Emission from Warm Gas The backgrounds are The backgrounds are Non X-ray particles Non X-ray particles CXB CXB Virgo Hot ICM (kT~2keV) Virgo Hot ICM (kT~2keV) Local hot bubble (kT~0.07 keV) Local hot bubble (kT~0.07 keV) Milky way halo (kT~0.2 keV) Milky way halo (kT~0.2 keV) LHB and MWH temperature are studied by Lumb et al. 2002 Contribution from North Polar Spur ? Contribution from North Polar Spur ? PN spectrum from 247 arcmin 2 area around the QSO

11. Ringberg workshop May 3-5 2004/ Noriko Yamasaki11 Warm IGM or North Polar Spur ? The 0.2 keV component is 2.3 times higher than Lumb et al’s value (the reported fluctuation is ~35 %) The 0.2 keV component is 2.3 times higher than Lumb et al’s value (the reported fluctuation is ~35 %) Strongly suggested that the emission coma from IGM, but some contribution from NPS can not be excluded because the edge of Loop I emission is hard to determined. Strongly suggested that the emission coma from IGM, but some contribution from NPS can not be excluded because the edge of Loop I emission is hard to determined. The 0.2 keV component is an upper limit of the emission from the IGM. The 0.2 keV component is an upper limit of the emission from the IGM. (Contours from RASS 3/4keV band )

12. Ringberg workshop May 3-5 2004/ Noriko Yamasaki12 Combining the absorption lines and excess emission OVIII absorption line at cz=1253 km/s OVIII absorption line at cz=1253 km/s Consistent with a narrow line (<5.1 eV), which means  z<0.02 or 80 Mpc Consistent with a narrow line (<5.1 eV), which means  z<0.02 or 80 Mpc N OVIII ~6.2x10 16 cm -2 (assuming a velocity dispersion of 2100 km/s) N OVIII ~6.2x10 16 cm -2 (assuming a velocity dispersion of 2100 km/s) OVIII/OVII ion ration >1.7 ( kT>0.2 keV) OVIII/OVII ion ration >1.7 ( kT>0.2 keV) Emission of kT~0.21 keV Emission of kT~0.21 keV Assuming N OVIII =fAZn e L and EM~n e 2 LS Assuming N OVIII =fAZn e L and EM~n e 2 LS *N (column density),ne(electron density), A(relative O abundance), Z(Solar abundance), L(depth), S(Area) n e <6x10 -5 cm -3 (A/0.1)(f/0.4) (  <250) L> 9Mpc (A/0.1) -2 (f/0.4) -2 If the redshift of the Oxygen lines are measured by as good energy resolution as by gratings, we can determine the origin of the soft X-ray emission. If the redshift of the Oxygen lines are measured by as good energy resolution as by gratings, we can determine the origin of the soft X-ray emission.

13. Ringberg workshop May 3-5 2004/ Noriko Yamasaki13 Oxygen emission lines as WHIM probe Why oxygen emission lines? Why oxygen emission lines? Most abundant metal Most abundant metal Good tracers at T=10 6 -10 7 K Good tracers at T=10 6 -10 7 K Not restricted to region toward background QSO Not restricted to region toward background QSO Suitable for systematic WHIM survey OVII :574, 561, 568, 665 eV OVIII :653 eV

14. Ringberg workshop May 3-5 2004/ Noriko Yamasaki14 Simulation for Oxygen lines from WHIM Cosmological SPH simulation in  =0.3,  =0.7,  8 =1.0,h=0.7  -CDM with 128 3 each for DM and gas (Yoshikawa et al. 2001) ->gas density and temperature (potential) Cosmological SPH simulation in  =0.3,  =0.7,  8 =1.0,h=0.7  -CDM with 128 3 each for DM and gas (Yoshikawa et al. 2001) ->gas density and temperature (potential) Various Metallicity models based on the density Various Metallicity models based on the density Convolve the emissivity (continuum and lines) over the lightcone from z=0 to z=0.3 Convolve the emissivity (continuum and lines) over the lightcone from z=0 to z=0.3 Add Galactic emission lines (McCammon et al. 2002) and CXB continuum to simulate energy spectrum Add Galactic emission lines (McCammon et al. 2002) and CXB continuum to simulate energy spectrum z=0 z=0.3 (See Yoshikawa et al. 2003 for details)

15. Ringberg workshop May 3-5 2004/ Noriko Yamasaki15 Surface Brightness of the Sky 0.03 < z < 0.04 0.09 < z < 0.11 Bolometric X-ray emission 0.03 < z < 0.04 0.09 < z < 0.11 0.0< z < 0.3 O VII and O VIII line emission

16. Ringberg workshop May 3-5 2004/ Noriko Yamasaki16 Simulated Spectra with  E=2 eV: Region A:  =0.88deg 2, S=100cm 2, T=3x10 5 sec With and without Galactic emission & CXB A

17. Ringberg workshop May 3-5 2004/ Noriko Yamasaki17 Properties of the detected baryons Each symbol indicate the temperature and the over- density of gas at each simulation grid (4x4 smoothed pixels over the sky and Dz=0.3/128) S x > 3x10 -10 [erg/s/cm 2 /sr] S x > 6x10 -11 [erg/s/cm 2 /sr] S x > 10 -11 [erg/s/cm 2 /sr]

18. Ringberg workshop May 3-5 2004/ Noriko Yamasaki18 Proposed small mission --DIOS-- (Diffuse Intergalactic Oxygen Surveyor) Use TES micro calorimeter array for good energy resolution 4-reflecting X-ray mirror to obtain wide field-of-view 3D mapping of Oxygen lines of 10x10 degree 2 sky into z=0.3  E=2eV and S  =100cm 2 deg 2 with small (<500kg) satellite

19. Ringberg workshop May 3-5 2004/ Noriko Yamasaki19 Expected S/N for OVIII line T exp =10 6 sec T exp =10 5 sec T exp =10 4 sec  E=2 eV and SW=100deg 2 cm 2 is necessary

20. Ringberg workshop May 3-5 2004/ Noriko Yamasaki20 TES calorimeter array XRS -type detector is hard to be enlarged more than 64 pixels.. XRS -type detector is hard to be enlarged more than 64 pixels.. ISAS/TMU team achieved 6eV resolution with a single pixel TES ISAS/TMU team achieved 6eV resolution with a single pixel TES Array structure model with absorbers has been fabricated Array structure model with absorbers has been fabricated Signal multiplexing is under developing (AC bias & multi-input SQUID) Signal multiplexing is under developing (AC bias & multi-input SQUID)

21. Ringberg workshop May 3-5 2004/ Noriko Yamasaki21 4-stage X-ray mirror 4-stage reflection wide field of view (50’) with short focal length (70cm) 4-stage reflection wide field of view (50’) with short focal length (70cm) Suitable to small mission Suitable to small mission Angular resolution of 3’ not so good, but enough to observe diffuse mission Angular resolution of 3’ not so good, but enough to observe diffuse mission Fabrication test has been started at Nagoya Univ. Fabrication test has been started at Nagoya Univ.

22. Ringberg workshop May 3-5 2004/ Noriko Yamasaki22 Current satellite design Total Weight & Mass :<400kg, 1.5m h x 1.5m  (within ASAP-5 criteria) Total Weight & Mass :<400kg, 1.5m h x 1.5m  (within ASAP-5 criteria) Weight and power budget Weight and power budget bus: 200kg and 170W bus: 200kg and 170W instrument :200 kg and 280W instrument :200 kg and 280W Orbit: 550km, inclination <30 degree Orbit: 550km, inclination <30 degree Attitude control: 3-axis bias momentum Attitude control: 3-axis bias momentum Accuracy <0.5 arcmin. Accuracy <0.5 arcmin. Life and weight depends on cryogenic system Life and weight depends on cryogenic system ADR 3 He sorption cooler 2-stage Stirling cooler 3 He J-T cooler 20K 1.8K 0.4K <50mK TES

23. Ringberg workshop May 3-5 2004/ Noriko Yamasaki23 DIOS Performance Effective area > 100 cm 2 Field of view 50' diameter SSSS ~100 cm 2 deg 2 Angular resolution 3' (16 x 16 pix) Energy resolution 2 eV (FWHM) Energy range 0.1 - 1 keV Mission life > 5 yr Larger S  than those of Con-X and XEUS

24. Ringberg workshop May 3-5 2004/ Noriko Yamasaki24 Summary Warm-hot IGM (10 5 K<T<10 7 K) is the most plausible missing baryon candidate. Warm-hot IGM (10 5 K<T<10 7 K) is the most plausible missing baryon candidate. X-ray will be a window to the missing baryon. But the contamination from the Galactic hot gas should be excluded. X-ray will be a window to the missing baryon. But the contamination from the Galactic hot gas should be excluded. Oxygen line mapping with fine energy resolution will reveals the large scale structure of baryons in the Universe. Oxygen line mapping with fine energy resolution will reveals the large scale structure of baryons in the Universe. For that purpose, not a large X-ray observatory but an alternative approach like DIOS is required. For that purpose, not a large X-ray observatory but an alternative approach like DIOS is required.