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Diffuse Galactic X-ray Emission & the Galactic Centre. Bob Warwick University of Leicester. Accreting Black-holes in the Nearby Galaxy M101. OPTICAL. X-RAY. A Normal Face-on Galaxy – M101. Why are X-rays Important?. Identified phases of the Galactic ISM:

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Diffuse galactic x ray emission the galactic centre l.jpg

Diffuse Galactic X-ray Emission & the Galactic Centre

Bob Warwick

University of Leicester



Slide3 l.jpg

A Normal Face-on Galaxy – M101

Why are X-rays Important?

  • 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

0.3-1.0 keV

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

(Warwick et al. 2005 in prep.)


Slide4 l.jpg

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


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408 MHz

Haslam et al. 1982

Snowden et al. 1997


Chandra mosaic of the galactic centre region l.jpg
Chandra Mosaic of the Galactic Centre Region

Wang, Gotthelf & Lang (2002)


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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


Slide8 l.jpg

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 10 6 k plasma in the local galaxy l.jpg

T = 106.5 K

T = 106.1 K

Distribution of ~ 106 K Plasma in the Local Galaxy

Galactic Anti-Centre

Galactic Centre

GALACTIC PLANE

Snowden (2002)


Slide10 l.jpg

Shadowing of the ¼ keV SXRB in Draco

RAS ¼ keV

IRAS 100 micron

Burrows & Mendenhall 1991; Snowden et al. 1991


Distribution of 10 6 k plasma in the local galaxy11 l.jpg
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)


Slide12 l.jpg

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



Slide14 l.jpg

Hot gas in a Galaxy Group Latitude

Diffuse emission from a WHIM filament

Void in the WHIM structure

Fang et al, 2005


Slide15 l.jpg

XMM-Newton EPIC Instrument Latitude

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


Slide16 l.jpg

XMM MIRRORS Latitude


Slide17 l.jpg

XMM EPIC CCD CAMERAS Latitude

MOS CCDs

pn CCD


Measuring the spectrum of the diffuse xrb with the epic ccds l.jpg
Measuring the Spectrum of the Diffuse XRB with the EPIC CCDs Latitude

pn

Instrumental fluorescent lines

MOS

Particle continuum

Energy (keV)


Slide19 l.jpg

WHIM FILAMENT Latitude

Simulated Spectra


Slide20 l.jpg

Topics Latitude

  • 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 10 6 k plasma in the local ism l.jpg
Distribution of ~10 Latitude6 K Plasma in the Local ISM

T = 106.6 K

T = 106.1 K

Galactic Centre

Galactic Anti-Centre

Snowden (2002)



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Soft X-ray Spectra of the North Polar Spur Latitude

Willingale et al. (2003)



Slide25 l.jpg

ROSAT ALL-SKY SURVEY - ¾ keV IMAGE Latitude

Ophiuchus Dark Cloud


Slide26 l.jpg

X-ray Shadowing in the Ophiuchus Molecular Cloud Latitude

EPIC PN SPECTRUM: ON/OFF CLOUD

0.2 Energy (keV) 1 2

Image: X-ray 0.5-0.9 keV

Contours: IRAS 100 micron

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



Slide28 l.jpg

EPIC MOS SPECTRA FOR THE GALACTIC BULGE REGION Latitude

0.5,-2.6

0.0,0.0

1.1,-3.8

0.4,-5.4

0.5,-8.0

0.0,-11.9

345,+12

345,+24


Slide29 l.jpg

Topics Latitude

  • 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 l.jpg

6. 7 keV line Latitude

Excellent Tracer

Galactic

Center

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)


Spectrum of the galactic ridge l.jpg
Spectrum of the Galactic Ridge Latitude

  • 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)


Slide32 l.jpg

Point source contribution Latitude

Ebisawa et al (2005)

Is the Hard X-ray Galactic Ridge due to

  • Truly diffuse emission?

  • The superposition of point sources?


Slide33 l.jpg

Ebisawa et al. (2003,2005 Latitude)

Is the Hard X-ray Galactic Ridge due to

  • Truly diffuse emission?

  • The superposition of point sources?


Xgps i survey after point source removal l.jpg
XGPS-I Survey after Point Source Removal Latitude

0.4-1.4 keV

2-6 keV


Xgps i survey after point source removal35 l.jpg

G20.7-0.1 Latitude

G20.0-0.2

G19.6-0.2

G21.8-0.2=Kes 69

Radio 20 cm

XGPS-I Survey after Point Source Removal

2-6 keV


Variation of the 2 6 kev surface brightness of the galactic x ray ridge with l b l.jpg
Variation of the 2-6 keV surface brightness of the Galactic X-ray Ridge with (l,b)

25.0o

5.0o

Galactic Longitude

-0.5o

0.0o

+0.5o

Galactic Latitude


Slide37 l.jpg

The 6.7 keV iron line – the key diagnostic? X-ray Ridge with (l,b)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 gasASCA 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 l.jpg

Equivalent width of 6.4 keV Fe fluorescence line < 50 eV X-ray Ridge with (l,b)

6.7 keV iron line

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

Raw

Background

Background-subtracted

Preliminary Only


Slide39 l.jpg

Topics X-ray Ridge with (l,b)

  • 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


Slide40 l.jpg

XMM-NEWTON GALACTIC CENTRE SURVEYS X-ray Ridge with (l,b)

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


Slide41 l.jpg

0.0 X-ray Ridge with (l,b)o

-0.2o

0.2o

0.0o

Sgr A - Radio Arc Region

0.5-1.4 keV X-ray

Sgr A*

1E 1743.1-2843

Galactic Latitude

-0.2o

Galactic Longitude


Slide42 l.jpg

0.0 X-ray Ridge with (l,b)o

-0.2o

0.2o

0.0o

Sgr A - Radio Arc Region

2-4.5 keV X-ray

Arches Cluster

Sgr A*

1E 1743.1-2843

Galactic Latitude

Sgr A East SNR

-0.2o

Galactic Longitude


Slide43 l.jpg

0.0 X-ray Ridge with (l,b)o

-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

NT X-ray Threads

-0.2o

Galactic Longitude


Slide44 l.jpg

0.0 X-ray Ridge with (l,b)o

-0.2o

0.2o

0.0o

Sgr A - Radio Arc Region

6-9 keV X-ray

Sgr A*

Transient

Transient

Galactic Latitude

NT X-ray Threads

G0.13-0.13

Transient

-0.2o

Galactic Longitude


Slide45 l.jpg

2-6 keV band X-ray Ridge with (l,b)

2.4 keV S line

6.7 keV Fe line

6.4 keV Fe line


Slide46 l.jpg

Spectral Extraction Region X-ray Ridge with (l,b)

4.5- 6 keV Continuum

Celestial Coordinates


Slide47 l.jpg

X-ray Spectrum from the Annular Region around Sgr A X-ray Ridge with (l,b)

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


Slide48 l.jpg

Intrinsic width of Fe 6.7 keV line 27 +/- 13 eV X-ray Ridge with (l,b)

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


Slide49 l.jpg

S XV X-ray Ridge with (l,b)

Fe XXV

Fe K

8 keV thermal

1 keV thermal

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


Slide50 l.jpg

a X-ray Ridge with (l,b)x

bx

cx

4.5-6 keV Continuum

6.4 keV Iron Line

2.4 keV Sulphur Line

6.7 keV Iron Line


Slide51 l.jpg

a = 1.8 (Z~3 ; LECRe component) X-ray Ridge with (l,b)

b = 0.75 (Z ~1 ; 1 keV plasma)

c = 3.7 (Z=1 ; 8 keV plasma)


Slide52 l.jpg

Surface brightness versus radius X-ray Ridge with (l,b)

Emissivity ~ r -1.3

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


Slide53 l.jpg

The GC Bipolar Lobes X-ray Ridge with (l,b)

observed by Chandra

Galactic plane

Apparentlythermal outflowfrom SgrA*

6’ = 15 pc

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

Credit: Mark Morris


Slide54 l.jpg

+b X-ray Ridge with (l,b)

6’ = 15 pc

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



Slide56 l.jpg

(Muno et al. 2004) X-ray Ridge with (l,b)

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!

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


Slide57 l.jpg

Topics X-ray Ridge with (l,b)

  • 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


Slide58 l.jpg

ASCA X-ray Ridge with (l,b)

Sgr C

Fe K - Neutral Gas

Koyama et al. (1996)


Slide59 l.jpg

Churazov, Gilfanov & Sunyaev 1999 X-ray Ridge with (l,b)

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...)


Slide60 l.jpg

6.4 keV line X-ray Ridge with (l,b)

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-3


Slide61 l.jpg

Fe X-ray Ridge with (l,b)

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.

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


Slide62 l.jpg

Sgr B2 Giant Molecular Cloud X-ray Ridge with (l,b)

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)


Slide63 l.jpg

0.0 X-ray Ridge with (l,b)o

-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


Slide64 l.jpg

0.0 X-ray Ridge with (l,b)o

-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


Slide65 l.jpg

4.5-6 keV Continuum X-ray Ridge with (l,b)

thermal non-thermal

Correlation of the 4.5-6 keV X-ray continuum and the 6.4 keV line flux

6.4 keV Fe Line


Slide66 l.jpg

S = -0.3 (not constrained) X-ray Ridge with (l,b)

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


Slide67 l.jpg

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

30-35 km/s

15-20 km/s

20-25 km/s

25-30 km/s

35-40 km/s

40-45 km/s

45-50 km/s

6.4 keV line

Handa et al. (2005)


Slide68 l.jpg

Arches Cluster measured in SiO J = 1-0

90 light years

Distribution of 6.4 keV Iron Fluorescence near the Galactic Centre


Slide69 l.jpg

CS J = 2 –1 measured in SiO J = 1-0

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)


Some interesting unresolved questions relating to diffuse galactic x ray emission l.jpg
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?


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