# Presentation: 548244

## Missing Baryons at Low Redshift and Future Missions

- Takaya OhashiTokyo Metropolitan University
- Science of WHIM
- Suzaku search for WHIM
- Future prospects

- With Y. Takei, K. Sato, T. Tamura, A. Hoshino, T. Takahashi and others

## Thermal history of the universe

- WHIM (warm-hot intergalactic medium) will tell us the evolution of the hot-phase material in the universe

## Cosmic structure

- Cluster gas (107K)

- IGM (105-107K)

- Galaxies (~104K)

- size = 30 *h*-1 Mpc   5 deg at *z*=0.1

- Dark matter

- _WHIM_ (105-107 K) traces the cosmic large-scale structure  = “Missing baryon”
- Typical matter density: ** (=*n*/*n**B*)  = 10 - 100

- Yoshikawa et al. 2001, ApJ, 558, 520

## Oxygen emission line

- Kawahara et al. 06

- The best tool to explore dark baryon or WHIM in emission.
- Good energy resolution is essential to separate the ~100 times stronger Galactic/interplanetary emission

- OVII

- OVIII

## Baryon phase

- With X-ray absorption and emission lines, a wide area in the baryon phase space can be probed

- EDGE consortium

## Absorption in Mrk421 spectrum

- Nicastro et al. 05,Nature & ApJ
- Kaastra et al. 06, ApJ
- Rasmussen et al. 06, ApJ
- Nicastro et al. 07, submitted

- LETG: OVII (*z*=0.011) detection significance = 3.9**(*P**52bin=10-6)
- Not significant if behavior of (2) for 7 lines with redshift trials is considered
- No absorption sign in RGS data
- LETG feature might be transient? (outflow from Mrk421?)
- Much more convincing evidence needed: with EDGE and XEUS

- EW~3 eV

## Recent XMM results

- Werner et al. 2008: X-ray bridge between A222 and A223 (*z* = 0.21)
- kT ~ 0.9 keV, **~ 150, continuum only
- Bregman & Lloyd-Davis 2008: Local OVII absorption is due to Galactic halo (not by Local group medium)

- A222-A223 bridge

- EW vs M31 angle

- EW vs GC angle

- ?

## Suzaku study of cluster outskirts

- Snowden et al. 1995,1997

- Why Suzaku?

- XMM

- Suzaku

- Good resolving power for oxygen lines

## A2218, Sérsic159 and A399/401

-  A2218 (Takei et al. 07): *z* = 0.1756
- OVII line < 1 x 10-7 cm-2s-1arcmin-2
** < 270 (0.1*Z*, *L* = 2 Mpc, 2 x106K)
- Sérsic 159-03 (Werner et al. 07, A10): *z* = 0.0564
- Non-thermal excess over the cluster
- OVII line < 1.7 x 10-7 cm-2s-1arcmin-2
** < 410
- A399/A401 (Fujita et al. 07 PASJ Suzaku #2): Binary cluster at *z*=0.072 before merging
- OVII line < 1 x 10-7 cm-2s-1arcmin-2
** < 310

- 0.4*r*180

- 0.6*r*180

- A2218

- S159

## Coma outskirts

- XMM observation of Coma-11 field showed strong excess with OVII and OVIII lines, which are a few times stronger than the Galactic emission
- But, solar wind proton flux showed a flare-like feature during the XMM observation, which might have caused charge-exchange emission.

- XMM: Finoguenov et al. 03

- Coma-11

- excess

- Solar wind protons

- Coma with XMM

- Suzaku

## Coma-11 Suzaku result

- Suzaku data show no significant OVII or OVIII feature, with OVII upper limit 2.3 times lower than the XMM flux( < 2.4  10-7 cm-2 s-1 arcmin-2).
- Overdensity: **  < 900 (*L*/2Mpc)-1/2 (*Z*/0.1*Z*solar)-1/2

- Takei et al. 2008

## A2052

- Residual over ICM (1.5 keV), CXB and nominal Galactic emission

- Residual spectrum can be fit with either brighter Galactic foreground or redshifted emission with *kT* ~ 0.2 keV

- A nearby cluster: *z *= 0.0355 and *kT* = 3 keV
- Soft excess observed with XMM (Kaastra et al. 03)
- Suzaku observation: August 19-21, 2005  (very low contamination on XIS filter)
- 4 deg offset observation: July 14-15, 2007

- Tamura et al. 2008

- BI

- FI

*z*  0

- Excess

## More A2052

- Both A2052 and BGD regions are near the North Polar Spur, with enhanced soft X emission
- The excess component looks spatially uniform (Galactic?)
- If the 0.2 keV excess is due to WHIM-like gas at the cluster redshift *n*H ~ 1.7  10-4 cm-3 (** ~ 900)assuming *L* = 2 Mpc, *Z* = 0.1 solar

- RASS 3⁄4 keV map

- Radial profile of the excess

## A2142 offset regions

- The first cluster in which cold fronts were discovered by Markevitch et al. 2000.
- Offset regions along the merger axis were observed with Suzaku in August 2007
*kT* = 9 keV, *z* = 0.0909 *r*vir=2.66 Mpc =26.4’

- Two offset regions show similar diffuse spectrum

*R*180(2.7 Mpc)

- 2

- 3

- 1

## A2142 Suzaku results

- Offset-1

- Offset-2

- Offset-3

- T Crb: BGD

- A2142

- 1

- BGD was taken at 1.4 offset region
- Offset-2 region (90% statitical error)
- OVII:  7.13.710-8 cm-2s-1amin-2
- OVIII: 9.25.310-8 cm-2s-1amin-2
- OVII flux implies ** = 250  130
- However, systematic error (energy scale, resolution, contamination) is about 110-7 cm-2s-1amin-2, so it is still an upper limit  (< 1.2 10-7 cm-2s-1amin-2).

## Sculptor supercluster

- 6 X-ray clusters at *z* = 0.11, observed in Nov. 27-29, 2005
- XIS data suggested excess emission with *kT* ~ 0.8 keV (Kelley et al.: Suzaku 2006)
- A2811-offset region was further analyzed
- Upper limits (2**) to O lines:OVII: 1.21.4 x 10-7 cm-2s-1 arcmin-2    ** < 350 (2x106K, 2Mpc, 0.1*Z*)OVIII:  23 x 10-7 cm-2s-1 arcmin-2

- A2811 offset

## A1413

- A relaxed cluster at *z* = 0.143
- Suzaku offset pointing was done in Nov. 15-18, 2005
- 2** upper limits to O lines in 0.66 – 1 *r*180 (10’15’): OVII: 2.0 x 10-7 cm-2s-1arcmin-2 OVIII: 1.6 x 10-7 cm-2s-1arcmin-2with BGD in the same field
- With the same assumption of 0.1 solar, 2 x 106 K and *L* = 2 Mpc, ** < 400is implied by the OVII upper limit

*r*180

- XIS

- 0.66 – 1 *r*180

- Hoshino et al. in prep.

## Summary of Suzaku constraints

- Suzaku upper limits on Oxygen lines are factor of 3 -5 lower than the XMM “detection”.
- Understanding the spectrum of  Galactic emission is most important
- Detector background and solar wind process also cause significant effect on oxygen measurement
- Long on-off observation?

## Cluster outskirts: Simulation

*kT*

*n*e

*kT*

*n*e

- At *r*200: *kT* ~ 2 keV and *n*e ~ 3  10-5 cm-3(** ~ 180)
- Quite hot even at 1.5 *r*200 : may be too hot to look for oxygen lines
- Then, how clusters are connected to WHIM filaments?

- Kawahara priv. comm

- Mean hydrogen density

## Summary of Suzaku study

- WHIM or missing baryons carry important science about structure formation and chemical/thermal evolution of the universe
- Its detection is a challenge for X-ray astronomy
- Suzaku is giving fairly low upper limits (** < 300) , but actual density around clusters is ** ~100
- Suzaku may be able to find dense clamps of WHIM in cluster outskirts and in superclusters, which will be the first signature of WHIM

## Spectrum Röntgen Gamma

- Talks by G. Hasinger (eROSITA)and J-W den Herder (SXC)

## XENIA/EDGE and DIOS

- TES calorimeter array with 1024 pixels
- _DIOS_ (Diffuse Intergalactic Oxygen Surveyor, Japan) ... small mission ~400 kg
- _EDGE_ (Explorer of Diffuse emission and Gamma-ray burst Explosions) ... medium size ~2000 kg      XENIA (Kouveliotou, Piro, den Herder) for US proposal
- Launch: 2015 or later
- Very wide field of view (~ 1deg) with 4-reflection X-ray telescope
- Energy range < 2 keV

- DIOS: Japanese small satellite

- EDGE/XENIA: US-Europe-J

## Expected results

- Incident spectrum

- WHIM

- Galactic+

- OVII & OVIII > 3**

- 0.1-1 Msec exposure with EDGE/XENIA (*S*~ 1000 cm2 deg2) gives significant detection of WHIM filaments
- Combined detection of OVII and OVIII lines suppresses spurious features
- EDGE/XENIA has capability of absorption measurement against GRB afterglow  density and depth of the filament

- 5 deg x 5 deg at *z* = 0.2 (60 Mpc)

- 1 Msec

## Expectation from XEUS

- Kawahara et al. 06 computed the mock transmission spectra of the WHIM based on hydrodynamic simulation data.
- a light-cone output for 0 < *z* < 0.3
- mock spectra for a bright source
- Cosmological Hydrodynamic Simulation (Yoshikawa et al. 01)
- PPPM/SPH (1283 DM and gas particles, *L*box = 75*h*-1 Mpc)
- m = 0.3,  = 0.7, b = 0.015*h*-2,  *h* = 0.7, **8 = 1.0
- note: b is  ~30 % smaller than the recent estimate.

- OVII: *z*=0.26-0.30, 5 deg = 76 Mpc

*N*OVII=1015-1016 cm-2

- But, 60000 cm2 was assumed

## Simulated spectra

- Expected number of absorption system per LOS
-                            *S*/*N * 3
- OVII (574 eV)       1.71
- OVIII (654 eV)      0.43
- OVII and OVIII      0.41

- 3**

- EW=0.05 eV : 3*** *for 30 ksec                         with XEUS

- 9*****z*=0.29

- for 30 ksec obs.

*F*x = 1 x 10-12  (2-10 keV)

## NEXT

- Phase A since 2007
- Target Launch 2013
- Launch Vehicle : H2A

- NuStar (2011) / Simbol-X (2013)
- (Hard X-ray Imaging Only)

- Phase A study has started.
- A review required to start  Phase B will take place in May 2008.

- NeXT
- 2013-

*NEXT*
*New Exploration X-ray Telescope*

- Takahashi et al. 06, SPIE

## NeXT Baseline Configuration

**X-ray micro-calorimeter (small FOV)**

**X-ray CCD camera (Large FOV)**

**The first hard X-ray focus imaging**

**Soft Gamma-ray Detector**

- Wide-Band

- Soft X-ray Telescope

- Soft X-ray Telescope

- Soft X-ray
- Spectrometer

- Soft X-ray
- Imager

- Hard X-ray Telescope

- Hard X-ray
- Imager

## New Science brought by the power of micro calorimeter

**New Science brought by the power of micro calorimeter**

## Strategy of NEXT

- Combination of gas dynamics (SXS), hard X-ray image (HXT) and 300 keV spectrum (SGD):
- Complete picture of non-thermal process in galaxies and clusters: galactic winds and cluster mergers
- Obscured AGNs: hard-X and Fe-line to probe surrounding medium

- Fe-K line

## Microcalorimater(SXS)

- MLI

- Sunshade

- DeployableBench

- Solar power

- Radiator

- Radiator

- Radiator

- X-rays

- Hard X-ray Imagers
- (*HXI*)

- Soft X-ray Telescopes (*SXT-S*, *SXT-I*)

- Microcalorimater(*SXS*)

- X-ray CCD(*SXI*)

- Focal Length = 12m

- Focal Length = 6m

- Hard X-ray Telescopes
- (*HXT*)

- Sunshade

- Soft γ-ray detectors
- (*SGD*)

## NeXT Performance

|  | Requirement |
| --- | --- |
| Hard X-ray Imaging System
(HXT+HXI)
5-80 keV | Angular resolution 60”
Effective Area 340cm2 @30 keV
Energy resolution 2 keV |
| Soft X-ray spectroscopy System
(SXT-S+SXS)
0.3-10 keV | Energy resolution 5-10 eV
In-orbit life 3 years
Sensor size 25 mm2 |
| Soft X-ray Imaging System
(SXT-I+SXI)
Requirement: 0.5-12 keV
Goal: 0.3-25 keV | Angular resolution 60”
Effective area 530cm2@6 keV
Energy resolution 150 eV
Imaging area size 5cmx5cm |
| Soft Gamma-ray Detector
(SGD)
10-300 keV | Detector background
1 x 10-5 ph cm-2 s-1 keV-1 |

## Telescope effective area

## Science Payloads
HXT: J, US
SXT:  J, US
HXI:  J, US
SXI:   J, US
SXS:  J, US, ND
SGD: J, US
Science working group and Joint Data Center (to be organized in this year)
US, Europe, and other countries
Joint System Engineering Team and Technology working group (to be organized in this year)
especially with US 

**Science Payloads**
**HXT: J, US**
**SXT:  J, US**
**HXI:  J, US**
**SXI:   J, US**
**SXS:  J, US, ND**
**SGD: J, US**
**Science working group and Joint Data Center ****(to be organized in this year)**
**US, Europe, and other countries**
**Joint System Engineering Team and Technology working group ****(to be organized in this year)**
**especially with US **

- International collaborations of NeXT

## Final summary

- Missing baryons (and accompanying missing dark matter) are important and only probed with X-ray observations
- Microcalorimeters (small *E*, wide area, angular coverage) can achieve various unique science (missing baryons, dynamics, chemistry...)
- Hopefully, NEXT (& SRG) will give a new momentum to X-ray astronomy