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Joint Chandra and Suzaku CCD Spectroscopy of Hard X-ray Emission in the Arches Cluster

Joint Chandra and Suzaku CCD Spectroscopy of Hard X-ray Emission in the Arches Cluster. Masahiro Tsujimoto Rikkyo Univ. Talk Plan. Arches Cluster & Galactic Center Chandra & Suzaku Observations Results & interpretations Discrete source. Extended emission. Summary.

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Joint Chandra and Suzaku CCD Spectroscopy of Hard X-ray Emission in the Arches Cluster

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  1. Joint Chandra and Suzaku CCD Spectroscopy of Hard X-ray Emissionin the Arches Cluster Masahiro Tsujimoto Rikkyo Univ. Chandra Fellow Symposium @ Boston, MA

  2. Talk Plan • Arches Cluster & Galactic Center • Chandra & Suzaku Observations • Results & interpretations • Discrete source. • Extended emission. • Summary Wang, D. Q. et al. (2006, ApJ) Tsujimoto, M. et al. (2006, PASJ) Chandra Fellow Symposium @ Boston, MA

  3. VLA 90cm HST/NICMOS (B=F110W, G=F160W, R=F205W) Arches GC GP 100pc 5” (0.2pc) Figer et al. (1999) LaRosa et al. (2000) 1. Arches Cluster & GC • One of the three massive young star clusters in GC. (Arches, Quintuplet, GC). • Located at ~25pc (projected dist.) from GC. • Total Mass > 7000 Mo; Size ~ 0.5 pc; Stellar Mass Density ~ 3x105 Mo/pc3. • Scale comparable only to NGC3603, W49A, Westerlund 1 (Our Galaxy) and R136 in 30 Dor. (LMC). Chandra Fellow Symposium @ Boston, MA

  4. Arches Suzaku/XIS GP Sgr A East (GC) Koyama et al. (2006) 1. Arches Cluster & GC • Intense & extended 6.4 keV emission in GC. • 6.4 keV line = Ka line of iron at low-ionization stages (hereafter “Fe II”). Presumably in dust. • The cause is unknown for a decade. • A 6.4 keV clump associated to AC. Purpose: To investigate the hard X-ray emission from AC, and to understand the origin of the 6.4 keV emission. Chandra Fellow Symposium @ Boston, MA

  5. ObsID=945 (t=50ks, q=7.1’) 2276 (10ks, 4.4’) 2284 (10ks, 7.6’) 4500 (100ks, 1.4’) b Decl l R.A. 2. Chandra/ACIS Observations A2 A1N A1S A1 A2 A1N A1S diffuse Chandra Fellow Symposium @ Boston, MA

  6. GP 6.4 keV (Fe II) 10pc 6.7keV (Fe XXV) 8-10 keV Arches 2. Suzaku/XIS Observations Sgr A East • Suzaku Observatory (July, 2005-) • X-ray Imaging-Spectometer: Four CCDs. Lowest background. • X-Ray Telescopes: Large EA (~590cm2 @8keV). HPD~1’. • Suzaku observations: ~100ks. Sept. 23 & 30, 2005. • Band-limited smoothed images. • A local excess at AC in all bands. • 8-10 keV resemble 6.4 keV image. Chandra Fellow Symposium @ Boston, MA

  7. diffuse A1N A1S A2 3. Results & Interpretationsa. Point-like Source S XV S XVI S XV S XVI • 3 bright point sources; • All src’s: thermal emission. • A2, A1S have 2T (kT~0.8, 6 keV). c.f. A debate among Yusef-Zadeh et al. (2002); Law & Yusef (2003); Wang et al. (2006) for 1T or 2T. • A1S: NH~2x1023/cm2. Lx (2.0-8.0 keV)~1035 erg/s. The brightest stellar X-ray source in our Galaxy. • Diffuse emission. • No thermal features. Fe II Fe XXV Fe XXV A2 A1N A1S diffuse S XV S XVI Chandra Fellow Symposium @ Boston, MA

  8. Lang et al. (2001) Figer et al. (2002) Keck/NIRSPEC VLA (8.5GHz) He I, Br g He II N III C IV He I 3. Results & Interpretationsa. Point-like Source A1N A1S • Bright X-ray sources in other wavelength. • 3 of the brightest 12 NIR sources with Minit>100Mo. • Wolf-Rayet stars (WN7). • Radio (thermal free-free cont.) counterparts (X-ray brightest = radio brightest). • Conversely, for the 12 brightest NIR sources, • 11 are WN7. All are bright in radio. • Only 3 are bright in X-ray. Others are fainter by x100. • Additional factor is necessary for luminous hard X-ray production. Binarity (“X-ray spec. binaries”)? A1N A1S A2 Chandra Fellow Symposium @ Boston, MA

  9. PL comp. 3. Results & Interpretationsb. Extended Emission • Hard-band XIS spectrum: spatially-unresolved, high S/N, < 12 keV. • Thermal features (Ca XIX Ka, Fe XXV Ka, Kb, Ni XXVII Ka) <- composite of point sources. • Non-thermal features (Fe II Ka, Kb; neutral. PL~12 keV.) <- diffuse emission. • Band-limited images: 6.4 (Fe II), 6.7 (Fe XXV), 8-10 (PL) keV • Similarity in 6.4 & 8-10 keV images. -> PL & 6.4/7.1 keV lines (FeII Ka/Kb) related in the underlying physics. • Two possibilities for the physical process. • X-ray photo-ionization (Koyama 1996; Sunyaev 1995) Fe K shell ionization & fluorescence (line) + Thomson scattering (cont). • Particle collision ionization (Wang 2006) Fe K shell ionization & vacancy filling (line) + Bremsstrahlung (cont.) • Two obs. tests: EWKa (1.5keV) & PL norm. (~2x10-4/s/keV@10keV). Thermal cont. Non- thermal cont. Chandra Fellow Symposium @ Boston, MA Non-thermal features Thermal features

  10. 3. Results & Interpretationsb. Extended Emission Scattered X-rays (diffuse emission) • X-ray photo-electric ionization. (X-rays are from the brightest discrete sources in AC). • Lack of Fe K edge alone is not evidence against photo-ionization. Optically-thin case is justified. NH (diffuse) ~ 6x1022/cm2. • Constraints for the incident photons. • Flat spectrum: I(E)∝E-G (G~1). • Flux:~3x107/(ne/102cm-3) /s/cm2/keV@10keV. • No source is found in the vicinity. • X-ray emission in AC is too weak for incident photons. … Scattered emission < Incident emission @ E>7.11 keV. Fe K edge (7.11keV) Incident X-rays (point sources) Chandra Fellow Symposium @ Boston, MA

  11. 3. Results & Interpretationsb. Extended Emission 2. Particle Collision Ionization. (Electrons accelerated in colliding stellar winds in AC.) • Accelerated electrons of 10-100 keV. • Electrons are “optically-thick” to the medium. (c.f. A 100 keV electron is stopped by a hydrogen column of ~4x1021/cm2). • Energy conversion rate ~ 10-5. • Constraints for injected electrons. • Number density: N(E)∝E-(G+1) (G~1). • Flux: 2x101 erg/s/cm2 (~103 eV/cm3). • Wind-accelerated electrons (protons, heavy ions, too) in AC are insufficient for the incident source. … Electron energy injection rate < Wind kinetic energy rate. Chandra Fellow Symposium @ Boston, MA

  12. Wang et al. (2006) 3. Results & Interpretations Low-mass stars High-mass stars X-radiation Stellar winds Wind collisions Magnetic field Irradiated cloud Non-spherical radiation? Magnetic turbulance? Time variation? Chandra Fellow Symposium @ Boston, MA

  13. 4. Summary • Results of a joint Chandra & Suzaku study of Arches cluster are presented. • Three bright point sources. • Thermal emission. Two-temperature plasma. • WN7 by NIR spectra. Large mass loss by 8.5 GHz flux. • A1S: Brightest stellar X-ray source in our Galaxy. Binary? • Extended emission. • Non-thermal emission. • Power-law & 6.4/7.1 keV emission related in underlying physics. • AC is insufficient for ionizing photon/particle source. “Abnormal” ideas are necessary. Thank you for your attention! Chandra Fellow Symposium @ Boston, MA

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