Galaxy Clusters & NHXM Galaxy Clusters & NHXM Silvano Molendi (IASF-Milano/INAF)

Innovative GC science with NHXM Can we perform innovative studies of galaxy clusters with NHXM?

High Energy Detector E > 10 keV 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 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 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/UL Non-thermal emission results are "controversial" Recent results from INTEGRAL and Suzaku are all UL, with one exception.

Inverse Compton 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 v s = c s x M ΔT/T ~ 4% ΔT/T ~ 10% T ~ 25 keV T ~ 10 keV Δv s /v s ~17% M measured from Chandra images, ΔM/M ~ 13%

Hard X-ray focusing mission HPD FOV FL E range Aeff HPD FOV FL E range Aeff FWHM m keV FWHM m keV NuStar 40” 12’ Astro-H 90” 9’ NHXM 20” 12’ To improve significantly wrt to competitors NHXM must devote attention to: broad band calibration broad band calibration minimization and characterization of bkg minimization and characterization of bkg

Broad Band Calibration / Perseus hard 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)

Perseus The difference btwn Chandra and EPIC measures is due to a cross calibration issue between EPIC and ACIS Caused by a problem in the calibration of the Chandra high energy effective areas recently identified by Chandra calibrators (David+07, Marshall+08) pn ACIS S3

Perseus Caused by a problem in the calibration of the Chandra high energy effective areas recently identified by Chandra calibrators (David+07, Marshall+08) A high quality calibration of the instrumentation is very important ACIS S3 pn

Perseus Caused by a problem in the calibration of the Chandra high energy effective areas recently identified by Chandra calibrators (David+07, Marshall+08) A high quality calibration of the instrumentation is very important ACIS S3 pn

Suzaku HXD vs BeppoSAX PDS Suzaku/HXD sensitivity comparable to Beppo-SAX/PDS altough the bkg/EffArea ratio is 4-5 times smaller?.. RXTEBeppo-SAX/PDSSuzaku/HXD PDS twin rocking collimators allowed a simultaneous measure of source and bkg. HXD relies on a background model based on bkg measures which are not simultaneous with sou measures.

Suzaku.. RXTEBeppo-SAX/PDSSuzaku/HXD Keeping your background low is important. Knowing to a high precision the intensity and shape of your background is also very important. PDS twin rocking collimators allowed a simultaneous measure of source and bkg. HXD relies on a background model based on bkg measures which are not simultaneous with sou measures.

Low Energy Detector keV 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 Background pn measured bkg comparable to SX LED expected bkg with AC off Hall et al. (08)

Instrumental 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 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 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 LEO

Sensitivity to low SB emissiom Depends upon: SB of source ~ Eff.Area SB of background (area in angular units) Figure of merit Eff.Area/SB bkg Compare Eff.Area/SB bkg for different experiments with Eff.Area/SB bkg for LED

Sensitivity to low SB emission LED/EPIC MOS | 5.4 LED/EPIC pn | LED/Swift XRT | LED/Suzaku FI | 1.2 LED/Suzaku BI | 1.6 Eff.Area 333cm 2

Sensitivity to low SB emission LED/EPIC MOS | LED/EPIC pn | LED/Swift XRT | LED/Suzaku FI | LED/Suzaku BI | Eff.Area Eff.Area 333cm 2 500cm 2

Sensitivity to low SB emission LED/EPIC MOS | LED/EPIC pn | LED/Swift XRT | LED/Suzaku FI | LED/Suzaku BI | Eff.Area Eff.Area Eff.Area 333cm 2 500cm 2 500cm 2 +LEO (2.5)

Sensitivity to low SB emission 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

Recomendations 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 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.)

Summary 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