Hard X-ray Emission and IC in Coma and Abell 3667 from Suzaku and XMM-Newton Craig Sarazin University of Virginia A3667 XIS images and radio contours Coma temperature map and PIN FOV Collaborators Kazuhiro Nakazawa (Univ. Tokyo) Abell 3667
Daniel R. Wik (Univ. Virginia) Coma Alexis Finoguenov (MPE, UMBC) XMM-Newton Yasushi Fukazawa, Naomi Kawano (Hiroshima Univ.) Susumu Inoue (NAOJ), Madoka Kawaharada (RIKEN) Takao Kitaguchi, Kazuo Makishima, Sho Okuyama (U. Tokyo) Kyoko Matsushita (Tokyo Univ. Sci) Motokazu Takizawa (Yamagata Univ.) Tracy E. Clarke (NRL, Interferometrics ) Cluster Radio Relics and Halos Diffuse, cluster-scale radio emission without
associated radio galaxy Steep radio spectra Only in merging clusters Cluster radio halos: central and symmetric Due to turbulent acceleration behind shocks (?) Cluster radio relics: peripheral and elongated Due to merger shock (re)acceleration (?) Should also emit hard X-rays by Inverse Compton scattering of CMB Measuring or Limiting the Magnetic Field
Measure both IC X-rays and synchrotron radio Radio E (rel. e) x UB HXR IC E (rel. e) x UCMB Detect both E (rel. e) & B Upper limit IC upper limit E (rel. e). lower limit B Coma Cluster Brightest non-cooling core X-ray cluster Brightest radio halo Color: X-ray ROSAT
Contours: Radio (Deiss et al. 1997) Coma Cluster IC Hard Xrays? Long history of searches Recent claimed detections BeppoSAX: FX = 1.5 x 10-11 ergs/cm2/s, 20-80 keV (Fusco-Femiano et al. 2004, 2007) RXTE: FX = 1.6 x 10-11 ergs/cm2/s, 20-80 keV (Rephaeli & Gruber 2002)
But, very controversial BeppoSAX: FX < 8.1 x 10-12 ergs/cm2/s, 20-80 keV (Rossetti & Molendi 2004, 2007) INTEGRAL: hard X-rays purely thermal (Renaud et al. 2006, Eckert et al. 2007) INTEGRAL/RXTE/ROSAT: hard X-rays purely thermal (Lutovinov et al. 2008) Swift/BAT: hard X-rays purely thermal (Ajello et al 2008)
Suzaku Observation of Coma 156 ksec (PIN), 31 May 4 June 2006 NXB model agrees well with Earthblocked flux and spectrum Model CXB Model AGN point srcs (small effect) Joint fit with XMM/Newton and/or Suzaku XIS to model thermal emission key! Joint XMM - PIN Analysis To PIN down the thermal emission . . . Mosaic of XMM/Newton exposures to cover cluster
(Schuecker et al. 2004; Finoguenov in this work) Extract XMM spectra in regions of ~constant PIN area Entire HXD FOV Contours of PIN spatial sensitivity in 10% intervals XMM 2-7.5 keV image, Schuecker et al. 2004
Joint XMM - PIN Analysis To PIN down the thermal emission . . . Mosaic of XMM/Newton exposures to cover cluster (Schuecker et al. 2004; Finoguenov in this work) Extract XMM spectra in regions of ~constant PIN area Weight by PIN area, combine Gives thermal spectrum as seen by PIN, correct shape and flux Fit PIN and XMM jointly
Coma: Spectral Fitting Results Single temperature model with no second component not a very good fit hard X-ray excess Addition of power-law improves fit Best-fit Single Temperature plus Power Law XMM Power Law (IC)
Suzaku PIN Coma: Spectral Fitting Results Single temperature model with no second component not a very good fit hard Xray excess Addition of power-law improves fit, but Best-fit = 1.46 flatter than radio spectrum Two-temperature model better than one temperature + power-law Hard excess due to thermal structure in gas?
Multi-Temperature Model XMM-Newton mosaic used to construct temperature map Combine models for regions weighted by PIN effective area Provides good fit to data with no adjustment of models or normalization Hard excess probably thermal Coma: Spectral Fitting Results (Cont.) Doesnt include systematic errors
NXB (non-X-ray background) 3% CXB XMM/Suzaku cross-calibration Power Law (IC) Coma: Spectral Fitting Results (Cont.) Doesnt include systematic errors NXB (non-X-ray background) 3% CXB XMM/Suzaku cross-calibration Take 90% errors, combine
Power-law not required Upper Limit on IC For = 2.0 (from radio) FX(20-80 keV) < 7.8 x 10-12 ergs/cm2/s (90% confidence), Factor of 2 below
BeppoSAX (Fusco-Femiano et al. 2004) and RXTE (Rephaeli & Gruber 2002) detections These detections inconsistent for any sensible But, FOV of PIN < BeppoSAX, RXTE Due to thermal hard X-ray emission? Lower limit B > 0.15 GG Consistent with Beq ~ 0.5 GG (Giovannini et al. 1993) Abell 3667 Merging Cluster XMM Briel et al. 2004; this work
Major merger along NW-SE axis z = 0.0552 Chandra Vikhlinin et al. 2000 Cold front, remnant of cool core of one subcluster Double Radio Relics
ROSAT (color), radio contours NW Radio Relic SE Radio Relic Rttgering et al. 1997 NW Radio Relic in Abell 3667 Brightest diffuse cluster source
3.7 Jy at 20 cm (Johnston-Hollitt 2004) Located at large projected radius ~2.2 Mpc expect weak B field Should be a very strong IC HXR source! Sarazin et al. 2007 3 Suzaku Observations XIS FOVs
HXD/PIN FOVs 3 observations, 3-7 May 2006 Exposures of ~20, ~17, ~78 ksec Intracluster Gas at Large Radii XIS 1-4 keV image XIS and Radio Surface Brightness Center
AGN 1-2 keV 2-4 keV 4-8 keV Radio NWR CXB Hot gas out to 42 arcmin = 2.6 Mpc virial radius (but, along merger axis of merging cluster?)
Joint XMM - PIN Analysis Mosaic of XMM/Newton exposures to cover cluster (Briel et al. 2004; this work) Extract XMM spectra in regions of ~constant PIN area Weight by PIN area, combine Gives thermal spectrum
as seen by PIN, correct shape and flux Fit PIN and XMM jointly XMM Image from mosaic Hard X-rays: PIN-XMM Results Detection of excess HXR Best-fit power-law = 3.2, much steeper than radio really thermal? Assuming power-law with = 2.1 (radio)
FX = 3.4 x 10-12 ergs/cm2/s 12-70 keV Doesnt include systematic errors!! PIN XMM Hard X-rays: PIN-XMM Results (Cont.) Systematic Errors: NXB: 5% CXB: 20% (HXR flux, cosmic variance) XMM/PIN calibration: 25%
FX < 7.6 x 10-12 ergs/cm2/s 12-70 keV BeppoSAX PDS FX < 9.3 x 10-12 ergs/cm2/s 12-70 keV (Nevalainen et al. 2004) Lower limit on B B > 0.5 G Tighter Limit from XIS XIS and Radio Surface Brightness Center AGN
1-2 keV 2-4 keV 4-8 keV Radio NWR Hard Xrays CXB No evidence for excess hard X-rays in XIS image or spectrum on radio relic
Tighter Limit from XIS (Cont.) Assume same spectral index at lower energies Assume XIS = thermal + IC Assume IC follows radio image Apply results to all of relic FX < 2.6 x 10-13 ergs/cm2/s 10 - 40 keV B > 2.2 G, very strong magnetic field at projected radius of ~2 Mpc !! Some previous evidence for a strong B in relic from Faraday rotation (Johnston-Hollitt 2004).
Evidence for Nonthermal Pressure of Relic 1-2 keV 2-4 keV 4-8 keV Radio Center NWR AGN Soft X-rays:
dip X-ray/radio anticorrelation CXB Significant nonthermal pressure support? Typical, or just due to merger and/or Component relic? ICM B Rel-e P (eV/cm3)
~1.2 > 0.1 < 0.4 Conclusions Coma (Wik et al. 2008) Upper limit on IC, below BeppoSAX & RXTE detections Hard excess probably thermal A3667 (Nakazawa et al. 2008) ICM extends out to 2.6 Mpc virial radius PIN has hard excess, but may be thermal, and <
systematic uncertainty FX < 7.8 x 10-12 ergs/cm2/s 12-70 keV E(rel. e) < 9 x 1061 ergs B > 0.5 G No IC in XIS image or spectra FX < 2.6 x 10-13 ergs/cm2/s 10 - 40 keV B > 2.2 G, very strong B at 2 Mpc Significant nonthermal pressure support in radio relic?
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