diffuse galactic x-ray emission & the galactic centre diffuse galactic x-ray emission & the...

Diffuse Galactic X-ray Diffuse Galactic X-ray Emission & the Galactic Emission & the Galactic

CentreCentre

Bob WarwickUniversity of Leicester

Accreting Black-holes in the Nearby Accreting Black-holes in the Nearby Galaxy M101Galaxy M101

OPTICAL X-RAY

A Normal Face-on Galaxy – M101A Normal Face-on Galaxy – M101

XMM-Newton source-removed EPIC image XMM-Newton source-removed EPIC image with GALEX UV contours superimposed with GALEX UV contours superimposed

(Warwick et al. 2005 in prep.)(Warwick et al. 2005 in prep.)

0.3-1.0 keV0.3-1.0 keV

• 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?Why are X-rays Important?

X-ray Emission from the Milky WayX-ray Emission from the Milky Way

Type of Emitter Number in Summed LxType of Emitter Number in Summed Lx Galaxy Galaxy 10 10 38 38 erg serg s-1-1

HMXRB HMXRB 30 ~3 30 ~3LMXRB 100 ~30 LMXRB 100 ~30 SNR ~500 <1 SNR ~500 <1 Low Lx Be Binaries ~10Low Lx Be Binaries ~1044 <1 <1CVs ~10CVs ~105 5 <1 <1 RSCVnRSCVn ~10 ~106 6 <1 <1 Late Type Stars 10Late Type Stars 1010 10 <1<1

Active Nucleus 1 <0.001Active Nucleus 1 <0.001

Diffuse Disk/GCDiffuse Disk/GC 1 1 ~3 ~3Diffuse BulgeDiffuse Bulge 1 ~20 1 ~20Diffuse Halo/Corona 1 ~10Diffuse Halo/Corona 1 ~10

Total ~60Total ~60

Snowden et al. 1997Snowden et al. 1997 Haslam et al. 1982Haslam et al. 1982

408 MHz408 MHz

Chandra Mosaic of the Galactic Chandra Mosaic of the Galactic Centre RegionCentre Region

Wang, Gotthelf & Lang (2002)Wang, Gotthelf & Lang (2002)

X-ray Astronomy Group

The Local Bubble, the Galactic Halo & BeyondThe Local Bubble, the Galactic Halo & Beyond

Loop 1 & the Galactic Bulge EmissionLoop 1 & the Galactic Bulge Emission

The Origin of the Hard Galactic RidgeThe Origin of the Hard Galactic Ridge

Hot Plasma in the Galactic Center RegionHot Plasma in the Galactic Center Region

Fluorescent X-rays from GC Molecular CloudsFluorescent X-rays from GC Molecular Clouds

Topics Topics

Distribution of ~ 10Distribution of ~ 1066 K Plasma in the Local Galaxy K Plasma in the Local Galaxy

Snowden Snowden (2002)(2002)

Galactic Galactic CentreCentre

Galactic Galactic Anti-Anti-CentreCentre

T = 10T = 106.56.5 K K

T = 10T = 106.16.1 K K

GALACTIC PLANEGALACTIC PLANE

Burrows & Mendenhall 1991; Snowden et al. 1991Burrows & Mendenhall 1991; Snowden et al. 1991

IRAS 100 micronIRAS 100 micron RAS ¼ keVRAS ¼ keV

Shadowing of the ¼ keV SXRB in DracoShadowing of the ¼ keV SXRB in Draco

Distribution of ~ 10Distribution of ~ 1066 K Plasma in the Local Galaxy K Plasma in the Local Galaxy

270270oo

T = 10T = 106.56.5 K K

T = 10T = 106.16.1 K K

9090oo

Draco Draco NebulaNebula

Cygnus Super BubbleCygnus Super Bubble

Simulated Spectrum of the Galactic Foreground at High LatitudeSimulated Spectrum of the Galactic Foreground at High Latitude

Fang et al, 2005Fang et al, 2005

Local Hot BubbleLocal Hot Bubble

Active GalaxiesActive Galaxies

Galactic HaloGalactic Halo

IGM of Local Group ?IGM of Local Group ?

WHIM ?WHIM ?

Nicastro et al. (2005)Nicastro et al. (2005)

WHIM Absorption Along the Line of Sight to Markarian 421WHIM Absorption Along the Line of Sight to Markarian 421

Fang et al, 2005Fang et al, 2005

Hot gas in a Galaxy GroupHot gas in a Galaxy Group

Void in the WHIM structureVoid in the WHIM structure

Diffuse emission from a WHIM filamentDiffuse emission from a WHIM filament

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

pn CCD MOS CCDs

Measuring the Spectrum of the Diffuse XRB with the Measuring the Spectrum of the Diffuse XRB with the EPIC CCDsEPIC CCDs

Particle Particle continuumcontinuum

Instrumental Instrumental fluorescent linesfluorescent lines

Energy (keV)Energy (keV)

MOSMOS

Simulated SpectraSimulated Spectra

WHIM FILAMENTWHIM FILAMENT

Topics Topics

Distribution of ~10Distribution of ~1066 K Plasma in the Local ISM K Plasma in the Local ISM

Galactic Galactic CentreCentre

Galactic Anti-Galactic Anti-CentreCentre

T = 10T = 106.16.1 K K

T = 10T = 106.66.6 K K

ROSAT ALL-SKY SURVEY - ¾ keV IMAGEROSAT ALL-SKY SURVEY - ¾ keV IMAGE

Soft X-ray Spectra of the North Polar SpurSoft X-ray Spectra of the North Polar Spur

Willingale et al. (2003)Willingale et al. (2003)

Ophiuchus Dark Ophiuchus Dark CloudCloud

X-ray Shadowing in the Ophiuchus Molecular Cloud X-ray Shadowing in the Ophiuchus Molecular Cloud

0.2 Energy (keV) 1 2 0.2 Energy (keV) 1 2

EPIC PN SPECTRUM: EPIC PN SPECTRUM: ON/OFF CLOUD ON/OFF CLOUD

Mendes et al. (2005) reported in Breitschwerdt et al. (2005)Mendes et al. (2005) reported in Breitschwerdt et al. (2005)

Image: X-ray 0.5-0.9 keVImage: X-ray 0.5-0.9 keV

Contours: IRAS 100 micronContours: IRAS 100 micron

EPIC MOS SPECTRA FOR THE GALACTIC BULGE REGIONEPIC MOS SPECTRA FOR THE GALACTIC BULGE REGION

0.0,0.00.0,0.0

345,+24345,+24345,+12345,+12

0.0,-11.90.0,-11.90.5,-8.00.5,-8.0

0.4,-5.40.4,-5.41.1,-3.81.1,-3.8

0.5,-2.60.5,-2.6

Topics Topics

The Galactic X-ray RidgeThe Galactic X-ray Ridge

Narrow ridge evident in EXOSAT Galactic Plane Scan Narrow ridge evident in EXOSAT Galactic Plane Scan (Warwick et al. 1985)(Warwick et al. 1985)

Extensively studied in Ginga Extensively studied in Ginga & ASCA Surveys& ASCA Surveys (Yamauchi & Koyama 1993; (Yamauchi & Koyama 1993; Sugizaki et al. 2001)Sugizaki et al. 2001)

6. 7 keV line

Excellent Tracer Galactic Center

Identified as a significant Galactic feature by HEAO1 Identified as a significant Galactic feature by HEAO1 (Worrall et al. 1982)(Worrall et al. 1982)

Spectrum of the Galactic Ridge Spectrum of the Galactic Ridge Emission lines from highly ionized Si, Emission lines from highly ionized Si,

S, and Fe S, and Fe multi-temperature multi-temperature plasma models plasma models

Cosmic X-ray BackgroundCool

componentkT ~0.8 keV

Kaneda et al. (1997)Kaneda et al. (1997)

ASCA GIS 6.7 keV iron line6.7 keV iron line

kT ~ 10 keVkT ~ 10 keV

ORIGIN OF THE HARD COMPONENT?ORIGIN OF THE HARD COMPONENT?

Luminosity of 1.4 x 10^38 erg/sLuminosity of 1.4 x 10^38 erg/s

Energy Density ~10 eV/cm^3Energy Density ~10 eV/cm^3

Too hot to originate in SN activityToo hot to originate in SN activity

Unbound to Galactic DiskUnbound to Galactic Disk

Possible approaches to various aspects Possible approaches to various aspects of the problem:of the problem:

Magnetic reconnection & confinementMagnetic reconnection & confinement

Quasi-thermal plasmaQuasi-thermal plasma

LECRe – non-thermal contributionLECRe – non-thermal contribution

LECR ions & charge exchange LECR ions & charge exchange

See Tanaka (2002)See Tanaka (2002)

Ebisawa et al Ebisawa et al (2005)(2005)

Point source contributionPoint source contribution

Is the Hard X-ray Galactic Ridge due to Is the Hard X-ray Galactic Ridge due to – Truly diffuse emission?Truly diffuse emission?– The superposition of point sources?The superposition of point sources?

Ebisawa et al. (2003,2005Ebisawa et al. (2003,2005))

XGPS-I Survey after Point Source RemovalXGPS-I Survey after Point Source Removal

0.4-1.4 keV0.4-1.4 keV

2-6 keV2-6 keV

XGPS-I Survey after Point Source RemovalXGPS-I Survey after Point Source Removal

2-6 keV2-6 keV

Radio 20 cmRadio 20 cm

G20.7-0.1G20.7-0.1G19.6-0.2G19.6-0.2G20.0-0.2G20.0-0.2

G21.8-0.2=Kes 69G21.8-0.2=Kes 69

Variation of the 2-6 keV surface brightness of Variation of the 2-6 keV surface brightness of the Galactic X-ray Ridge with (l,b)the Galactic X-ray Ridge with (l,b)

-0.5-0.5oo 0.00.0oo +0.5+0.5oo

Galactic LatitudeGalactic Latitude

Galactic LongitudeGalactic Longitude25.025.0oo 5.05.0oo

The 6.7 keV iron line – the key diagnostic?The 6.7 keV iron line – the key diagnostic?

ASCA GIS: 6.61+/-0.02 keV (Kaneda et al. 1997) ASCA GIS: 6.61+/-0.02 keV (Kaneda et al. 1997) nei plasma or a blend of thermal emission with 6.4 keV nei plasma or a blend of thermal emission with 6.4 keV iron fluorescence from LECRe excitation of cold gasiron fluorescence from LECRe excitation of cold gas

ASCA SIS: Blend of 6.70 keV (He-like) & 6.96 keV (H-like) ASCA SIS: Blend of 6.70 keV (He-like) & 6.96 keV (H-like) lines (Tanaka 2002) lines (Tanaka 2002) ~ collisional equilibrium thermal plasma at ~ 8 keV ~ collisional equilibrium thermal plasma at ~ 8 keV very similar spectrum to that seen in Galactic Centre! very similar spectrum to that seen in Galactic Centre!

Chandra: 6.52 +0.08/-0.14 keV (Ebisawa et al. 2005)Chandra: 6.52 +0.08/-0.14 keV (Ebisawa et al. 2005) consistent with ASCA GIS result! consistent with ASCA GIS result!

The X-ray Spectrum of the Galactic X-ray Ridge The X-ray Spectrum of the Galactic X-ray Ridge measured by XMM-Newtonmeasured by XMM-Newton

Raw Raw

BackgroundBackground

Background-subtractedBackground-subtracted 6.7 keV iron line6.7 keV iron line

Equivalent width of 6.4 Equivalent width of 6.4 keV Fe fluorescence keV Fe fluorescence

line < 50 eVline < 50 eV

Preliminary OnlyPreliminary Only

Topics Topics

WIDE-FIELD SURVEYAnne Decourchelle SaclayBob Warwick LeicesterMasaaki Sakano LeicesterPeter Predehl MPEDelphine Porquet MPE

SGR A* MONITORINGAndrea Goldwurm Saclayet al

XMM-NEWTON GALACTIC CENTRE SURVEYS

~ 250 ks ~ 400 ks

Sgr A - Radio Arc Region 0.5-1.4 keV X-ray

Galactic Longitude

Sgr A*Sgr A*

1E 1743.1-28431E 1743.1-2843

Sgr A - Radio Arc Region 2-4.5 keV X-ray

Galactic Longitude

1E 1743.1-28431E 1743.1-2843

Sgr A*Sgr A*Arches Arches ClusterCluster

Sgr A East SNRSgr A East SNR

Sgr A - Radio Arc Region 4.5-6 keV X-ray

Galactic Longitude

1E 1743.1-28431E 1743.1-2843

Sgr A*Sgr A*

Arches Arches ClusterCluster

NT X-ray NT X-ray ThreadsThreads

Sgr A East SNRSgr A East SNR

Sgr A - Radio Arc Region 6-9 keV X-ray

Galactic Longitude

G0.13-0.13G0.13-0.13

Sgr A*Sgr A*

NT X-ray NT X-ray ThreadsThreads

Transient

2-6 keV band

6.4 keV Fe line

2.4 keV S line

6.7 keV Fe line

Spectral Extraction Region

4.5- 6 keV Continuum

Celestial CoordinatesCelestial Coordinates

X-ray Spectrum from the Annular Region around Sgr A

1-3 keV Thermal

7-10 keV Thermal and/or

Non-Thermal

Si XIII S XV

Ca XIXAr XVII

Al & Si Fluorescence Lines

Fe-line Spectrum from the Annular Region around Sgr A

Fe NeutralFe XXV

Fe XXVI

6.4 keV 6.70 keV 6.96 keV

Intrinsic width of Fe 6.7 keV line 27 +/- 13 eV

Fe XXV

1 keV 1 keV thermalthermal

8 keV 8 keV thermalthermal

Non-thermal bremmstrahlung Non-thermal bremmstrahlung plus 6.4 keV iron fluorescence plus 6.4 keV iron fluorescence from LECRe + molecular gasfrom LECRe + molecular gas

4.5-6 keV Continuum 6.4 keV Iron Line

6.7 keV Iron Line 2.4 keV Sulphur Line

b x c x

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 Distribution of 6.7 keV line as a tracer of the hard “thermal” componenthard “thermal” component

Corrected for 6.7 keV line Corrected for 6.7 keV line emission originating in the emission originating in the softer ~ 1 keV plasmasofter ~ 1 keV plasma

Surface brightness versus radiusSurface brightness versus radius

Emissivity ~ r Emissivity ~ r -1.3-1.3

6’ = 15 pc

Chandra smoothed, point-source removed 2 - 4.7 keV image.

alactic plane

Apparentlythermal outflowfrom SgrA*

Credit: Mark MorrisCredit: Mark Morris

The GC Bipolar Lobes

observed by Chandra

Ratio: soft (2– 4.7 keV) / hard (4.7 – 8 keV) emission(most point sources removed)

6’ = 15 pc

Locations of point sources (Muno et al.)

Hot Diffuse Gas in the Galactic CentreTwo 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

(Muno et al. 2004)

Latter due to sources? A population A population of 2 x 10^5 CV-of 2 x 10^5 CV-like sources like sources with Lx ~ with Lx ~ 10^31 erg/s at 10^31 erg/s at the Galactic the Galactic Centre would Centre would do the trick!do the trick!

Then how about Then how about trying the same trying the same trick for the trick for the Galactic Ridge!Galactic Ridge!

Topics Topics

Koyama et al. (1996)

Fe K - Neutral Gas

An X-ray echo of the past activity of Sgr A* ?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 NEBULAE

X-ray Reflection From Cold Near-Neutral MatterX-ray Reflection From Cold Near-Neutral Matter

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

dense neutral clouds

Fe K line

•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.

Alternative Model: Excitation by Cosmic-ray ElectronsAlternative Model: Excitation by Cosmic-ray Electrons

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

6.4 keV line

Chandra Observations – Murakami et al. (2001)

F line = 5.6 x 10-5 photon/cm2/s

E.W. = 2.2 keV

NFe = 3.4 x 1019 Fe cm-2

Sgr B2 Giant Molecular Cloud

Sgr A - Radio Arc Region

Galactic Longitude

Radio 20 & 90 cm

6.4 keV Fe fluorescence

Sgr A - Radio Arc Region

6.4 keV Fe line

Galactic Longitude

CS (J=1-0) 10-40 km/s

6.4 keV Fe fluorescence

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

thermal non-thermal

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

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

MOS 1/2

Correspondence of X-ray 6.4 keV line with Molecular Gas Correspondence of X-ray 6.4 keV line with Molecular Gas measured in SiO J = 1-0measured in SiO J = 1-0

6.4 keV line6.4 keV line

Handa et al. (2005)Handa et al. (2005)

35-40 km/s35-40 km/s 40-45 km/s40-45 km/s 45-50 km/s45-50 km/s

25-30 km/s25-30 km/s 30-35 km/s30-35 km/s20-25 km/s20-25 km/s15-20 km/s15-20 km/s

Distribution of 6.4 keV Iron Fluorescence near the Galactic Centre

90 light years

Arches Cluster

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

Some Interesting Unresolved Questions Some Interesting Unresolved Questions Relating to Diffuse Galactic X-ray EmissionRelating 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?

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