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

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Presentation on theme: "Fluorescent Iron-Line Emission in the Galactic Centre Bob Warwick University of Leicester, UK."— Presentation transcript:

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

2 WIDE-FIELD SURVEY Anne DecourchelleSaclay Bob WarwickLeicester Masaaki SakanoLeicester Peter Predehl MPE Delphine PorquetMPE SGR A* MONITORING Andrea GoldwurmSaclay et al XMM-NEWTON GALACTIC CENTRE SURVEYS ~ 250 ks~ 400 ks

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

4 X-ray echo of the past activity of Sgr A* ? An X-ray echo of the past activity of Sgr A* ? Churazov, Gilfanov & Sunyaev 1999 Fluorescence of giant molecular clouds illuminated by a flare on Sgr A* producing L X ~10 39 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...) X-RAY REFLECTION NEBULAE

5 X-ray Reflection From Cold Near-Neutral Matter X-rays 6.4 keV line Reflection models predict: Neutral Fe K alpha Line Eq. Width ~ 150 eV (wrt direct continuum) Neutral Fe K alpha Line Eq. Width > 1 keV (Z = 1) (wrt reflected continuum) Significant iron-K edge on reflected continuum, N Fe ~ 2 x 10 19 Fe cm -2 dense neutral clouds Fe K  line

6 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 in SNR interactions and/or young, massive stellar clusters (Yusef-Zadeh 2003) Alternative Model: Excitation by Cosmic-ray Electrons Fe Models predict: Neutral Fe K alpha Line Eq. Width ~0.55-0.85 keV (Z = 1) Significantly smaller iron-K edge on non-thermal bremsstrahlung continuum Tatischeff 2005

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

8 6.4 keV line Chandra Observations – Murakami et al. (2001) F line = 5.6 x 10 -5 photon/cm 2 /s E.W. = 2.2 keV N Fe = 3.4 x 10 19 Fe cm -2 Sgr B2 Giant Molecular Cloud

9 6.4 keV line 6.7 keV line 90 cm Radio Continuum4 – 6 keV Continuum XMM-Newton Observations Decourchelle et al. 6.4 keV line Iron-K edge Power-Law + Mekal Model Photon Index = -0.8 F line = 7.1 x 10 -5 photon/cm 2 /s E.W. = 1.8 keV N Fe = 3.3 x 10 19 Fe cm -2

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

11 XX-ray Reflection Nebulosity in Sgr C Region CS (J=1-0) -70 to –60 km/s90 cm Radio Continuum 6.4 keV Fe line 2-9 keV X-rays F line = 6.4 x 10 -6 photon/cm 2 /s E.W. = 1.7 keV

12 Sgr A - Radio Arc Region4.5-6 keV X-ray 0.0 o -0.2 o 0.2 o 0.0 o Galactic Longitude Galactic Latitude -0.2 o 1E 1743.1-2843 Sgr A* Arches Cluster Sgr A East SNR

13 Sgr A - Radio Arc Region6.4 keV line 0.0 o -0.2 o 0.2 o 0.0 o Galactic Longitude Galactic Latitude -0.2 o G0.13-0.13 Cloud Sgr A* Arches Cluster Sgr A East SNR Filament 1 Filament 2 90 light years

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

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

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

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

18 X-ray Spectrum of G0.13-0.13 Cloud On-Cloud Regions Power-Law + Gaussian Line Model: Photon Index ~ 1.9 NH = 2.3 x 10 23 H cm -2 F line = 2.4 x 10 -5 photon/cm 2 /s E.W. = 1.45 keV N Fe < 1 x 10 19 Fe cm -2 S = -0.3 (not constrained) NH = 1.7 x 10 23 H cm -3 Z = 2.9 pn MOS 1/2

19 Spectral Extraction Region 4.5- 6 keV Continuum

20 S XV Fe XXV Fe K 

21 4.5-6 keV Continuum 6.4 keV Iron Line 6.7 keV Iron Line2.4 keV Sulphur Line a x b xb x c x

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 Iron 6.7 keV line (black) Iron 6.4 keV line (blue) 2-6 keV +0.1 o 0.0 o

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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