Diffuse Galactic Xray Emission

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Diffuse Galactic X-ray Emission the Galactic
Centre
Bob Warwick University of Leicester
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Accreting Black-holes in the Nearby Galaxy M101
OPTICAL
X-RAY
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(No Transcript)
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• 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
  lt1
• Low Lx Be Binaries 104
  lt1
• CVs 105
  lt1
• RSCVn 106 lt1
• Late Type Stars 1010
  lt1
• Active Nucleus 1
  lt0.001
• Diffuse Disk/GC 1 3
• Diffuse Bulge 1 20
• Diffuse Halo/Corona 1
  10

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Snowden et al. 1997
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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

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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

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Distribution of 106 K Plasma in the Local Galaxy
Galactic Anti-Centre
Galactic Centre
GALACTIC PLANE
Snowden (2002)
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Shadowing of the ¼ keV SXRB in Draco
RAS ¼ keV
IRAS 100 micron
Burrows Mendenhall 1991 Snowden et al. 1991
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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)
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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
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WHIM Absorption Along the Line of Sight to
Markarian 421
Nicastro et al. (2005)
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Hot gas in a Galaxy Group
Diffuse emission from a WHIM filament
Void in the WHIM structure
Fang et al, 2005
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XMM-Newton EPIC Instrument Large Effective
Area 2000 cm2 _at_ 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 _at_ 6 keV
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XMM MIRRORS
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XMM EPIC CCD CAMERAS
MOS CCDs
pn CCD
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Measuring the Spectrum of the Diffuse XRB with
the EPIC CCDs
pn
Instrumental fluorescent lines
MOS
Particle continuum
Energy (keV)
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Simulated Spectra
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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

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Distribution of 106 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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ROSAT ALL-SKY SURVEY - ¾ keV IMAGE
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Soft X-ray Spectra of the North Polar Spur
Willingale et al. (2003)
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Willingale et al. (2003)
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ROSAT ALL-SKY SURVEY - ¾ keV IMAGE
Ophiuchus Dark Cloud
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X-ray Shadowing in the Ophiuchus Molecular Cloud
Image X-ray 0.5-0.9 keV Contours IRAS 100 micron
Mendes et al. (2005) reported in Breitschwerdt et
al. (2005)
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ROSAT ALL-SKY SURVEY - ¾ keV IMAGE
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EPIC MOS SPECTRA FOR THE GALACTIC BULGE REGION
0.5,-2.6
0.0,0.0
0.4,-5.4
1.1,-3.8
0.0,-11.9
0.5,-8.0
345,24
345,12
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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

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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)
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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 1038 erg/s
• Energy Density 10 eV/cm3
• 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)
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• Is the Hard X-ray Galactic Ridge due to
• Truly diffuse emission?
• The superposition of point sources?

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

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XGPS-I Survey after Point Source Removal
0.4-1.4 keV
2-6 keV
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XGPS-I Survey after Point Source Removal
2-6 keV
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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
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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 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!
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The X-ray Spectrum of the Galactic X-ray Ridge
measured by XMM-Newton
Raw Background Background-subtracted
Preliminary Only
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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

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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
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Sgr A - Radio Arc Region
0.5-1.4 keV X-ray
Sgr A
1E 1743.1-2843
Galactic Latitude
-0.2o
Galactic Longitude
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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
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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
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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
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2-6 keV band
2.4 keV S line
6.4 keV Fe line
6.7 keV Fe line
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Spectral Extraction Region
4.5- 6 keV Continuum
Celestial Coordinates
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X-ray Spectrum from the Annular Region around Sgr
A
Si XIII
7-10 keV Thermal and/or
Non-Thermal
S XV
Ar XVII
Ca XIX
Fe
1-3 keV Thermal
Al Si Fluorescence Lines
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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
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8 keV thermal
1 keV thermal
Non-thermal bremmstrahlung plus 6.4 keV iron
fluorescence from LECRe molecular gas
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4.5-6 keV Continuum
6.4 keV Iron Line
6.7 keV Iron Line
2.4 keV Sulphur Line
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a 1.8 (Z3 LECRe component) b 0.75 (Z 1
1 keV plasma) c 3.7 (Z1 8 keV plasma)
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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
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The GC Bipolar Lobes observed by Chandra
Galactic plane
Apparentlythermal outflowfrom SgrA
6 15 pc
Chandra smoothed, point-source removed 2 - 4.7
keV image.
Credit Mark Morris
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b
6 15 pc
Ratio soft (2 4.7 keV) / hard (4.7 8 keV)
emission(most point sources removed)
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Locations of point sources (Muno et al.)
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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 105 CV-like sources with
Lx 1031 erg/s at the Galactic Centre would do
the trick!
Then how about trying the same trick for the
Galactic Ridge!
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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

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ASCA
Fe K? - Neutral Gas
Koyama et al. (1996)
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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
LX1039 erg/s, for ?t gt 10 yrs, 300 yrs ago.
(Sunyaev et al. 1993, Koyama et al. 1996,
Murakami et al. 2001, Revnivtsev et al.2004...)
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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 gt 1
keV (Z 1) (wrt reflected continuum) Significant
iron-K edge on reflected continuum, NFe 2 x
1019 Fe cm-3
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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
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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)
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Sgr A - Radio Arc Region
Radio 20 90 cm
90 cm
Galactic Latitude
6.4 keV Fe fluorescence line
-0.2o
Galactic Longitude
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Sgr A - Radio Arc Region
CS (J1-0) 10-40 km/s
6.4 keV Fe line
Galactic Latitude
6.4 keV Fe fluorescence line
-0.2o
Galactic Longitude
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4.5-6 keV Continuum
Correlation of the 4.5-6 keV X-ray continuum and
the 6.4 keV line flux
6.4 keV Fe Line
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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 lt 1 x 1019 Fe
cm-2
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Correspondence of X-ray 6.4 keV line with
Molecular Gas measured in SiO J 1-0
30-35 km/s
25-30 km/s
20-25 km/s
15-20 km/s
35-40 km/s
40-45 km/s
45-50 km/s
6.4 keV line
Handa et al. (2005)
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Distribution of 6.4 keV Iron Fluorescence near
the Galactic Centre
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Arches Cluster
2-6 keV
0.0o
0.1o
Iron 6.7 keV line (black) Iron 6.4 keV line
(blue)
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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?