Diffuse Galactic X-ray Emission & the Galactic Centre Bob Warwick University of Leicester

Accreting Black-holes in the Nearby Galaxy M101 OPTICAL X-RAY

Why are X-rays Important? A Normal Face-on Galaxy – M101 Identified phases of the Galactic ISM: Very hot: log T > 7.5 i.e. KT > 3 keV. Hot: 6 < log T < 7.5, i.e. 0.1 < kT < 3 keV Coronal: 5 < log T < 6 Warm: log T ~ 4, e.g. WIM, WNM. Cold: log T 1 - 3 e.g. Molecular clouds Why are X-rays Important? A Normal Face-on Galaxy – M101 XMM-Newton source-removed EPIC image with GALEX UV contours superimposed (Warwick et al. 2005 in prep.) 0.3-1.0 keV

X-ray Emission from the Milky Way Type of Emitter Number in Summed Lx Galaxy 10 38 erg s-1 HMXRB 30 ~3 LMXRB 100 ~30 SNR ~500 <1 Low Lx Be Binaries ~104 <1 CVs ~105 <1 RSCVn ~106 <1 Late Type Stars 1010 <1 Active Nucleus 1 <0.001 Diffuse Disk/GC 1 ~3 Diffuse Bulge 1 ~20 Diffuse Halo/Corona 1 ~10 Total ~60

Haslam et al. 1982 408 MHz Snowden et al. 1997

Chandra Mosaic of the Galactic Centre Region Wang, Gotthelf & Lang (2002)

Topics The Local Bubble, the Galactic Halo & Beyond Loop 1 & the Galactic Bulge Emission The Origin of the Hard Galactic Ridge Hot Plasma in the Galactic Center Region Fluorescent X-rays from GC Molecular Clouds

Topics The Local Bubble, the Galactic Halo & Beyond Loop 1 & the Galactic Bulge Emission The Origin of the Hard Galactic Ridge Hot Plasma in the Galactic Center Region Fluorescent X-rays from GC Molecular Clouds

Distribution of ~ 106 K Plasma in the Local Galaxy T = 106.5 K T = 106.1 K Galactic Anti-Centre Galactic Centre GALACTIC PLANE Snowden (2002)

Shadowing of the ¼ keV SXRB in Draco IRAS 100 micron RAS ¼ keV Burrows & Mendenhall 1991; Snowden et al. 1991

Distribution of ~ 106 K Plasma in the Local Galaxy T = 106.5 K Draco Nebula T = 106.1 K 270o 90o Cygnus Super Bubble Snowden (2002)

Simulated Spectrum of the Galactic Foreground at High Latitude Local Hot Bubble Active Galaxies Galactic Halo IGM of Local Group ? WHIM ? Fang et al, 2005

WHIM Absorption Along the Line of Sight to Markarian 421 Nicastro et al. (2005)

Fang et al, 2005 Hot gas in a Galaxy Group Diffuse emission from a WHIM filament Void in the WHIM structure Fang et al, 2005

XMM-Newton EPIC Instrument Large Effective Area: ~ 2000 cm2 @ 1 keV Good Imaging Capability: PSF(FWHM) 6 arcsec Wide Field of View: ~30 arcmin diameter Broad Bandpass: 0.3-12 keV Good Spectral Resolution: 120 eV @ 6 keV

XMM MIRRORS

XMM EPIC CCD CAMERAS MOS CCDs pn CCD

Measuring the Spectrum of the Diffuse XRB with the EPIC CCDs pn Instrumental fluorescent lines MOS Particle continuum Energy (keV)

Simulated Spectra WHIM FILAMENT

Topics The Local Bubble, the Galactic Halo & Beyond Loop 1 & the Galactic Bulge Emission The Origin of the Hard Galactic Ridge Hot Plasma in the Galactic Center Region Fluorescent X-rays from GC Molecular Clouds

Distribution of ~106 K Plasma in the Local ISM T = 106.6 K T = 106.1 K Galactic Centre Galactic Anti-Centre Snowden (2002)

ROSAT ALL-SKY SURVEY - ¾ keV IMAGE

Soft X-ray Spectra of the North Polar Spur Willingale et al. (2003)

Willingale et al. (2003)

ROSAT ALL-SKY SURVEY - ¾ keV IMAGE Ophiuchus Dark Cloud

X-ray Shadowing in the Ophiuchus Molecular Cloud Image: X-ray 0.5-0.9 keV Contours: IRAS 100 micron 0.2 Energy (keV) 1 2 EPIC PN SPECTRUM: ON/OFF CLOUD Mendes et al. (2005) reported in Breitschwerdt et al. (2005)

ROSAT ALL-SKY SURVEY - ¾ keV IMAGE

EPIC MOS SPECTRA FOR THE GALACTIC BULGE REGION 0.0,0.0 0.5,-2.6 1.1,-3.8 0.4,-5.4 0.5,-8.0 0.0,-11.9 345,+12 345,+24

Topics The Local Bubble, the Galactic Halo & Beyond Loop 1 & the Galactic Bulge Emission The Origin of the Hard Galactic Ridge Hot Plasma in the Galactic Center Region Fluorescent X-rays from GC Molecular Clouds

The Galactic X-ray Ridge Identified as a significant Galactic feature by HEAO1 (Worrall et al. 1982) Narrow ridge evident in EXOSAT Galactic Plane Scan (Warwick et al. 1985) Extensively studied in Ginga & ASCA Surveys (Yamauchi & Koyama 1993; Sugizaki et al. 2001) 6. 7 keV line Excellent Tracer Galactic Center

Spectrum of the Galactic Ridge Emission lines from highly ionized Si, S, and Fe  multi-temperature plasma models ORIGIN OF THE HARD COMPONENT? Luminosity of 1.4 x 10^38 erg/s Energy Density ~10 eV/cm^3 Too hot to originate in SN activity Unbound to Galactic Disk Possible approaches to various aspects of the problem: Magnetic reconnection & confinement Quasi-thermal plasma LECRe – non-thermal contribution LECR ions & charge exchange See Tanaka (2002) ASCA GIS 6.7 keV iron line kT ~ 10 keV Cosmic X-ray Background Cool component kT ~0.8 keV Kaneda et al. (1997)

Is the Hard X-ray Galactic Ridge due to Truly diffuse emission? The superposition of point sources? Ebisawa et al (2005) Point source contribution

Is the Hard X-ray Galactic Ridge due to Truly diffuse emission? The superposition of point sources? Ebisawa et al. (2003,2005)

XGPS-I Survey after Point Source Removal 0.4-1.4 keV 2-6 keV

XGPS-I Survey after Point Source Removal 2-6 keV G20.7-0.1 G19.6-0.2 G20.0-0.2 G21.8-0.2=Kes 69 Radio 20 cm

Variation of the 2-6 keV surface brightness of the Galactic X-ray Ridge with (l,b) Galactic Longitude -0.5o 0.0o +0.5o Galactic Latitude

The 6. 7 keV iron line – the key diagnostic. ASCA GIS: 6. 61+/-0 The 6.7 keV iron line – the key diagnostic? ASCA GIS: 6.61+/-0.02 keV (Kaneda et al. 1997)  nei plasma or a blend of thermal emission with 6.4 keV iron fluorescence from LECRe excitation of cold gas ASCA SIS: Blend of 6.70 keV (He-like) & 6.96 keV (H-like) lines (Tanaka 2002)  ~ collisional equilibrium thermal plasma at ~ 8 keV  very similar spectrum to that seen in Galactic Centre! Chandra: 6.52 +0.08/-0.14 keV (Ebisawa et al. 2005)  consistent with ASCA GIS result!

The X-ray Spectrum of the Galactic X-ray Ridge measured by XMM-Newton Equivalent width of 6.4 keV Fe fluorescence line < 50 eV 6.7 keV iron line Raw Background Background-subtracted Preliminary Only

Topics The Local Bubble, the Galactic Halo & Beyond Loop 1 & the Galactic Bulge Emission The Origin of the Hard Galactic Ridge Hot Plasma in the Galactic Center Region Fluorescent X-rays from GC Molecular Clouds

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

Sgr A - Radio Arc Region 0.5-1.4 keV X-ray 0.0o -0.2o 0.2o -0.2o Galactic Latitude -0.2o Galactic Longitude

Sgr A - Radio Arc Region 2-4.5 keV X-ray 0.0o -0.2o 0.2o -0.2o Arches Cluster Sgr A* 0.0o -0.2o 0.2o 1E 1743.1-2843 Galactic Latitude Sgr A East SNR -0.2o Galactic Longitude

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

Sgr A - Radio Arc Region 6-9 keV X-ray 0.0o -0.2o 0.2o -0.2o Sgr A* Transient 0.0o -0.2o 0.2o Transient Galactic Latitude NT X-ray Threads G0.13-0.13 Transient -0.2o Galactic Longitude

2-6 keV band 2.4 keV S line 6.7 keV Fe line 6.4 keV Fe line

Spectral Extraction Region 4.5- 6 keV Continuum Celestial Coordinates

7-10 keV Thermal and/or Non-Thermal X-ray Spectrum from the Annular Region around Sgr A Si XIII S XV 7-10 keV Thermal and/or Non-Thermal Ar XVII Ca XIX Fe 1-3 keV Thermal Al & Si Fluorescence Lines

Fe-line Spectrum from the Annular Region around Sgr A 6.4 keV 6.70 keV 6.96 keV Fe XXV Fe Neutral Fe XXVI Intrinsic width of Fe 6.7 keV line 27 +/- 13 eV

Fe K S XV Fe XXV 8 keV thermal 1 keV thermal Non-thermal bremmstrahlung plus 6.4 keV iron fluorescence from LECRe + molecular gas

a x b x c x 4.5-6 keV Continuum 6.4 keV Iron Line 2.4 keV Sulphur Line

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

Distribution of 6.7 keV line as a tracer of the hard “thermal” component Corrected for 6.7 keV line emission originating in the softer ~ 1 keV plasma Surface brightness versus radius Emissivity ~ r -1.3

The GC Bipolar Lobes observed by Chandra Credit: Mark Morris Galactic plane Apparently thermal outflow from SgrA* 6’ = 15 pc Chandra smoothed, point-source removed 2 - 4.7 keV image. Credit: Mark Morris

+b 6’ = 15 pc Ratio: soft (2– 4.7 keV) / hard (4.7 – 8 keV) emission (most point sources removed)

Locations of point sources (Muno et al.)

Hot Diffuse Gas in the Galactic Centre Two temperature components: 0.8-1.2 keV  attributable to supernovae & the GC outflow ~8.0 keV  implied energy if diffuse and unbounded ~1040 erg s-1 Latter due to sources? A population of 2 x 10^5 CV-like sources with Lx ~ 10^31 erg/s at the Galactic Centre would do the trick! (Muno et al. 2004) Then how about trying the same trick for the Galactic Ridge!

Topics The Local Bubble, the Galactic Halo & Beyond Loop 1 & the Galactic Bulge Emission The Origin of the Hard Galactic Ridge Hot Plasma in the Galactic Center Region Fluorescent X-rays from GC Molecular Clouds

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

An X-ray echo of the past activity of Sgr A* ? X-RAY REFLECTION NEBULAE 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 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...)

X-ray Reflection From Cold Near-Neutral Matter Fe K line dense neutral clouds X-rays 6.4 keV line 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-3

Alternative Model: Excitation by Cosmic-ray Electrons Cosmic-ray electrons E ~ 10 keV – 1 GeV 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 young, massive stellar clusters (Yusef-Zadeh 2003) Radio data establish a large population of GeV electrons in the inner 300 pc. Fe Models predict: Neutral Fe Kalpha Line Eq. Width ~0.55-0.85 keV (Z = 1) Significantly smaller iron-K edge on non-thermal bremsstrahlung cont. Tatischeff 2005

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)

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

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

Correlation of the 4.5-6 keV X-ray continuum and the 6.4 keV line flux 4.5-6 keV Continuum Correlation of the 4.5-6 keV X-ray continuum and the 6.4 keV line flux thermal non-thermal 6.4 keV Fe Line

X-ray Spectrum of G0.13-0.13 Cloud S = -0.3 (not constrained) NH = 1.7 x 1023 H cm-3 Z = 2.9 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

Correspondence of X-ray 6 Correspondence of X-ray 6.4 keV line with Molecular Gas measured in SiO J = 1-0 15-20 km/s 20-25 km/s 25-30 km/s 30-35 km/s 35-40 km/s 40-45 km/s 45-50 km/s 6.4 keV line Handa et al. (2005)

Distribution of 6.4 keV Iron Fluorescence near the Galactic Centre 90 light years Arches Cluster

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

Some Interesting Unresolved Questions Relating to Diffuse Galactic X-ray Emission What is the origin of the Galactic X-ray halo and does the emission extend into the IGM of the Local Group and beyond? Can we determine the X-ray properties and nature of the extended Galactic Bulge against the confusion of LOOP 1? What is the origin of the Galactic X-ray Ridge? Is the bright central concentration of hard “thermal” emission seen at the Galactic Centre really due to a diffuse component? Is the iron-line fluorescence seen throughout the Galactic Centre Region excited by photon illumination or cosmic ray electrons?