Galaxy ClustersGalaxy Clusters& &

NHXMNHXM

Silvano Molendi Silvano Molendi (IASF-Milano/INAF)(IASF-Milano/INAF)

Innovative GC science Innovative GC science with NHXMwith NHXM

Can we perform innovative studies of galaxy clusters with

NHXM?

High Energy Detector E > 10 High Energy Detector E > 10 keVkeV

• Measure thermal emission in

exceptional systems (i.e. massive

systems undergoing mergers)

• Explore with high sensitivity the

region beyond the thermal cutoff

Non-Thermal processes Non-Thermal processes

• Bulk of the emission is thermal, non-thermal mechanisms are potentially very important, provide clues on the physical process presiding over the formation and evolution of clusters.

• In some objects, evidence of non-thermal processes has been known for quite some time. Radio observations indicate that merging clusters are often the site of cluster-wide synchrotron emission (radio haloes & relics).

B field B field • B fields can be estimated through radio

measurements (Faraday rotation, minimum energy)

• Alternativelly from combination of radio and X-ray measurements.

• The latter rely on the detection of non-thermal emission at X-ray wavelengths (hard tails) attributed to IC scattering of microwave background photons by relativistic electrons.

• If the emission is not detected the upper limit on the X-ray flux converts to a lower limit on the B field

Detections/ULDetections/UL

Non-thermal emission results are "controversial"

Recent results from INTEGRAL and Suzaku are all UL, with one exception.

Inverse Compton Inverse Compton detections detections

From detailed simulations on a few systems

we found that

If IC reported from BeppoSAX and RXTE

detections are real:

detection and possibly spatial/spectral

characterization

If not:

tighter upper limit, detection maybe if

emission is concentrated

• Clusters form via merging of smaller mass concentrations.

• In the course of a merger, a significant fraction of the energy is dissipated by shocks and turbulence

• The bulk of the energy dissipated by shocks goes into heating ions.

• A small fraction of the energy may go into accelerating particles

• Typical shock velocities ~2000 km/s• Observationally shocks are difficult to

detect

Shocks in ICM

Shock in 1E0657

Markevitch+(07)

Best example of shock:

“Bullet Cluster”

Core of sub-structure already

gone through cluster

SX 100 ks simulation

vs = cs x M

ΔT/T ~ 4%ΔT/T ~ 4% ΔT/T ~ 10%ΔT/T ~ 10%

T ~ 25 T ~ 25 keVkeV

T ~ 10 T ~ 10 keVkeV

Δvs/vs ~17%

M measured from Chandra images, ΔM/M ~ 13%

Hard X-ray focusing mission

HPD FOV FL E range AeffHPD FOV FL E range Aeff FWHM m keV cm2@30keVFWHM m keV cm2@30keV

NuStar 40” 12’ 10 6-80 300 NuStar 40” 12’ 10 6-80 300 Astro-H 90” 9’ 12 0.1-80 300 Astro-H 90” 9’ 12 0.1-80 300 NHXM 20” 12’ 10 0.5-80 300NHXM 20” 12’ 10 0.5-80 300

To improve significantly wrt to competitors To improve significantly wrt to competitors

NHXM must devote attention to:NHXM must devote attention to: broad band calibrationbroad band calibration minimization and characterization of bkgminimization and characterization of bkg

Broad Band Calibration / Perseus Broad Band Calibration / Perseus hard tailhard tail

• Perseus hosts a mini radio halo • Detection of non-thermal emission

from Chandra data (Sanders & Fabian 05,07).

• Analysis of EPIC data using new calibrations and detailed treatment of bkg and systematics finds no evidence of non-thermal emission (SM & Gastaldello 09)

PerseusPerseus

The difference btwn Chandra and EPIC measures is due to a cross calibration issue between EPIC and ACIS

Caused by a problem Caused by a problem in the calibration of in the calibration of

the Chandra high the Chandra high energy effective areas energy effective areas recently identified by recently identified by Chandra calibrators Chandra calibrators

(David+07,(David+07,Marshall+08)Marshall+08)

ppnn

ACIS S3ACIS S3

PerseusPerseus

Caused by a problem Caused by a problem in the calibration of in the calibration of

the Chandra high the Chandra high energy effective areas energy effective areas recently identified by recently identified by Chandra calibrators Chandra calibrators

(David+07, (David+07, Marshall+08)Marshall+08)

A high quality calibration of the A high quality calibration of the instrumentation is very importantinstrumentation is very important

ACIS S3ACIS S3

ppnn

PerseusPerseus

Caused by a problem Caused by a problem in the calibration of in the calibration of

the Chandra high the Chandra high energy effective areas energy effective areas recently identified by recently identified by Chandra calibrators Chandra calibrators

(David+07, (David+07, Marshall+08)Marshall+08)

A high quality calibration of the A high quality calibration of the instrumentation is very importantinstrumentation is very important

ACIS S3ACIS S3

ppnn

Suzaku HXD vs BeppoSAX Suzaku HXD vs BeppoSAX PDSPDS

Suzaku/HXD sensitivity comparable to Beppo-SAX/PDS altough the bkg/EffArea ratio is

4-5 times smaller?

....

RXTERXTE

Beppo-SAX/PDSBeppo-SAX/PDS

Suzaku/HXDSuzaku/HXD

PDSPDS twin rocking twin rocking collimators allowed collimators allowed a simultaneous a simultaneous measure of source measure of source and bkg.and bkg.HXDHXD relies on a relies on a background model background model based on bkg based on bkg measures which are measures which are not simultaneous not simultaneous with sou measures.with sou measures.

SuzakuSuzaku

....

RXTERXTE

Beppo-SAX/PDSBeppo-SAX/PDS

Suzaku/HXDSuzaku/HXD

Keeping your background low is important.Keeping your background low is important.

Knowing to a high precision the intensity and Knowing to a high precision the intensity and shape of your background is also very important.shape of your background is also very important.

PDSPDS twin rocking twin rocking collimators allowed collimators allowed a simultaneous a simultaneous measure of source measure of source and bkg.and bkg.HXDHXD relies on a relies on a background model background model based on bkg based on bkg measures which are measures which are not simultaneous not simultaneous with sou measures.with sou measures.

Low Energy Detector 0.5-10 Low Energy Detector 0.5-10 keVkeV

• Explore with unprecedented

sensitivity low surface brightness

regions

• For all missions flown thus far the

instrumental background has been the

major obstacle precluding measures of

low sb regions

Instrumental BackgroundInstrumental Background

pn measured bkg comparable to SX LED expected bkg with AC off

Hall et al. (08)

Instrumental BackgroundInstrumental Background

Hall et al. (08)

pn measured bkg comparable to SX LED expected bkg with AC off

this is what happens when you turn the AC on

From SX to NHXMFrom SX to NHXM

• The major contribution to the instrumental bkg comes form p+ induced events.

• On LEO p+ are about 1/3 than on high orbit.

• We expect a factor of 3 or so reduction in instrumental background

• Place identical detector on both orbits

XMM MOS vs Swift MOSXMM MOS vs Swift MOS

• The major contribution to ins bkg

comes form p+ induced events.

• On LEO p+ are about 1/3 than on high

orbit.

• We expect a factor of 3 or so reduction

in ins background

Hall et al. (08b)

Dead time much less of a problem on LEODead time much less of a problem on LEO

Sensitivity to low SB Sensitivity to low SB emissiomemissiom

• Depends upon:

• SB of source ~ Eff.Area

• SB of background (area in angular

units)

• Figure of merit Eff.Area/SBbkg

• Compare Eff.Area/SBbkg for different

experiments with Eff.Area/SBbkg for

LED

Sensitivity to low SB Sensitivity to low SB emissionemission

---------------------LED/EPIC MOS | 5.4LED/EPIC pn | 2.8---------------------LED/Swift XRT | 1.2---------------------LED/Suzaku FI | 1.2LED/Suzaku BI | 1.6

Eff.Area 333cm2

Sensitivity to low SB Sensitivity to low SB emissionemission

-----------------------------LED/EPIC MOS | 5.4 7.9 LED/EPIC pn | 2.8 4.1 -----------------------------LED/Swift XRT | 1.2 1.7 -----------------------------LED/Suzaku FI | 1.2 1.7 LED/Suzaku BI | 1.6 2.4

Eff.Area Eff.Area 333cm2 500cm2

Sensitivity to low SB Sensitivity to low SB emissionemission

-------------------------------------LED/EPIC MOS | 5.4 7.9 19.7LED/EPIC pn | 2.8 4.1 10.3-------------------------------------LED/Swift XRT | 1.2 1.7 4.3-------------------------------------LED/Suzaku FI | 1.2 1.7 4.3LED/Suzaku BI | 1.6 2.4 6.0

Eff.Area Eff.Area Eff.Area 333cm2 500cm2 500cm2 +LEO (2.5)

Sensitivity to low SB Sensitivity to low SB emissionemission

LED has the potential to become the

most sensitive experiment to low SB

emission ever flown!

Provided we:

• Invest time and resources in BKG

related activities

• Increase effective areas in 2-10 keV

range

RecomendationsRecomendations We need a systemic approach to:

1.Background issue, SX heritage

2.Broad band calibration

Both recomendations are vital to study

of galaxy clusters and much of the

NHXM science!

A few examplesA few examples

In any broad band study of extragalactic

sources the spectrum in the hard band

will include a significant background

component!

A 15% cross calibration error btwn low

and high energy ranges can result in

errors of order unity in estimates of

secondary components (e.g. reflection

bump, cluster hard tails etc.)

SummarySummary Both High Energy Detector and Low Energy

Detector can provide important contributions to Cluster science

1. HED Non-thermal emission, thermal

emission in hot systems 2. LED Low surface brightness regions

To achieve these goals we need to devote particular attention to:

1. broad band calibration of LED + HED system

2. mininimmization and characterization of the bkg