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Fluorescent Iron-Line Emission in the Galactic Centre

Fluorescent Iron-Line Emission in the Galactic Centre. Bob Warwick University of Leicester, UK. XMM-NEWTON GALACTIC CENTRE SURVEYS. WIDE-FIELD SURVEY Anne Decourchelle Saclay Bob Warwick Leicester Masaaki Sakano Leicester Peter Predehl MPE Delphine Porquet MPE. SGR A* MONITORING

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Fluorescent Iron-Line Emission in the Galactic Centre

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  1. Fluorescent Iron-Line Emission in the Galactic Centre Bob Warwick University of Leicester, UK

  2. XMM-NEWTON GALACTIC CENTRE SURVEYS WIDE-FIELD SURVEY Anne Decourchelle Saclay Bob Warwick Leicester Masaaki Sakano Leicester Peter Predehl MPE Delphine Porquet MPE SGR A* MONITORING Andrea Goldwurm Saclay et al ~ 250 ks ~ 400 ks

  3. ASCA Sgr C Fe K - Neutral Gas Koyama et al. (1996)

  4. Churazov, Gilfanov & Sunyaev 1999 X-RAY REFLECTION NEBULAE An X-ray echo of the past activity of Sgr A* ? Fluorescence of giant molecular clouds illuminated by a flare on Sgr A* producing LX~1039 erg/s, for t > ~10 yrs, ~300 yrs ago. (Sunyaev et al. 1993, Koyama et al. 1996, Murakami et al. 2001, Revnivtsev et al. 2004...)

  5. 6.4 keV line X-rays X-ray Reflection From Cold Near-Neutral Matter Fe K line dense neutral clouds Reflection models predict: Neutral Fe Kalpha Line Eq. Width ~ 150 eV (wrt direct continuum) Neutral Fe Kalpha Line Eq. Width > 1 keV (Z = 1) (wrt reflected continuum) Significant iron-K edge on reflected continuum, NFe ~ 2 x 1019 Fe cm-2

  6. Fe Alternative Model: Excitation by Cosmic-ray Electrons • Radio data establish a large population of GeV electrons in the inner 300 pc. • Cosmic-ray electrons E ~ 10 keV – 1 MeV have significant cross-section for interaction with K-shell electrons (Valinia et al. 2000; Yusef-Zadeh et al. 2002) • Such cosmic rays maybe produced inSNR interactions and/oryoung, massive stellar clusters (Yusef-Zadeh 2003) Tatischeff 2005 Models predict: Neutral Fe Kalpha Line Eq. Width ~0.55-0.85 keV (Z = 1) Significantly smaller iron-K edge on non-thermal bremsstrahlung continuum

  7. CS J=1-0 -100km/s to +100 km/s Distribution of Iron 6.4 keV Line Emission XMM-Newton 0.6 o 0.0 o -0.6 o

  8. Sgr B2 Giant Molecular Cloud F line = 5.6 x 10-5 photon/cm2/s E.W. = 2.2 keV NFe = 3.4 x 1019 Fe cm-2 6.4 keV line Chandra Observations – Murakami et al. (2001)

  9. 6.4 keV line Iron-K edge XMM-Newton Observations Decourchelle et al. 6.4 keV line 6.7 keV line Power-Law + Mekal Model Photon Index = -0.8 Fline = 7.1 x 10-5 photon/cm2/s E.W. = 1.8 keV NFe = 3.3 x 1019 Fe cm-2 4 – 6 keV Continuum 90 cm Radio Continuum

  10. XX-ray Reflection Nebulosity in Sgr C Region 0.0o Chandra 1-8 keV (b-w image) XMM-Newton 2-9 keV (contours) -0.1o -0.2o -0.5o -0.6o Galactic Longitude

  11. F line = 6.4 x 10-6 photon/cm2/s E.W. = 1.7 keV XX-ray Reflection Nebulosity in Sgr C Region CS (J=1-0) -70 to –60 km/s 90 cm Radio Continuum 6.4 keV Fe line 2-9 keV X-rays

  12. 0.0o -0.2o 0.2o 0.0o Sgr A - Radio Arc Region 4.5-6 keV X-ray Arches Cluster Sgr A East SNR Sgr A* 1E 1743.1-2843 Galactic Latitude -0.2o Galactic Longitude

  13. 0.0o 90 light years -0.2o 0.2o 0.0o Sgr A - Radio Arc Region 6.4 keV line Arches Cluster Sgr A East SNR Sgr A* Filament 1 Galactic Latitude Filament 2 G0.13-0.13 Cloud -0.2o Galactic Longitude

  14. 0.0o -0.2o 0.2o 0.0o Sgr A - Radio Arc Region CS (J=1-0) 10-40 km/s 6.4 keV Fe line Galactic Latitude 6.4 keV Fe fluorescence line -0.2o Galactic Longitude

  15. 0.0o -0.2o 0.2o 0.0o Sgr A - Radio Arc Region Radio 20 & 90 cm 90 cm Galactic Latitude 6.4 keV Fe fluorescence line -0.2o Galactic Longitude

  16. 4.5-6 keV Continuum Background Cloud Correlation of the 4.5-6 keV X-ray continuum and the 6.4 keV line flux 6.4 keV Fe Line

  17. Chandra - Park et al. (2004) Line Equivalent Width XMM-Newton - Sgr A* Deep Field Neutral Fe K line flux Celestial Coordinates

  18. S = -0.3 (not constrained) NH = 1.7 x 1023 H cm-3 Z = 2.9 X-ray Spectrum of G0.13-0.13 Cloud pn MOS 1/2 Power-Law + Gaussian Line Model: Photon Index ~ 1.9 NH = 2.3 x 1023 H cm-2 Fline = 2.4 x 10-5 photon/cm2/s E.W. = 1.45 keV NFe < 1 x 1019 Fe cm-2 On-Cloud Regions

  19. Spectral Extraction Region 4.5- 6 keV Continuum

  20. S XV Fe XXV Fe K

  21. a x bx cx 4.5-6 keV Continuum 6.4 keV Iron Line 2.4 keV Sulphur Line 6.7 keV Iron Line

  22. a = 1.8 (Z~3 ; LECRe component) b = 0.75 (Z ~1 ; 1 keV plasma) c = 3.7 (Z=1 ; 8 keV plasma)

  23. Arches Cluster 6.4 keV line

  24. CS J = 2 –1 20 – 40 km/s Arches Cluster 2-6 keV 0.0o +0.1o Iron 6.7 keV line (black) Iron 6.4 keV line (blue)

  25. Conclusions The iron-K fluorescence line at 6.4 keV provides a unique tool for probing dense molecular gas in the Galactic Centre. Whether the fluorescence generally arises due to irradiation by hard X-rays or, alternatively, through an interaction with “suprathermal” cosmic-ray electrons remains uncertain. High sensitivity X-ray spectroscopy of bright 6.4 keV features should allow us to select those clouds which may be acting as “mirrors” of past outbursts on Sgr A*.

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