Discovery of Ka lines of neutral S, Ar, Ca, Cr,

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Discovery of Ka lines of neutral S, Ar, Ca, Cr,
Mn atoms from the Galactic center with Suzaku

• Masayoshi Nobukawa, Katsuji Koyama,
• Takeshi Go Tsuru, Syukyo G Ryu (Kyoto Univ.)

• Neutral Fe line from the Galactic center
• Discovery of neutral Ka lines of S, Ar, Ca, Cr,
  Mn
• What is the origin of the neutral lines ?
• Summary

Galactic center workshop 2009, shanghai, hope
hotel
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Neutral Fe line emission from the GC region
6.4 keV (neutral Fe-Ka) emission shows a clumpy
distribution in the Galactic center
region. Neutral clumps are correlated with
giant molecular clouds (Sgr B2, Radio Arc
regions)
X-ray binary 1E 1743.1-2843
Sgr A East (SNR)
Sgr B2
Sgr B1
M0.74-0.09
Sgr B2
Radio Arc
20 (50 pc)
G0.174-0.233
Radio Arc
Sgr B2
Molecular gas CS (J1-0)
Spectrum of Sgr B2 prominent neutral Fe line
strongly absorbed continuum (NH1024 cm-2)
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Other neutral lines ?
Lighter elements, S, Ar, Ca, Cr, Mn are expected
to exist in the molecular cloud.
Fe1
Ni
Mn
We searched for the neutral lines from these
elements using the Suzaku satellite.
solar abundance
3/11
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The strongest neutral clump
Other neutral lines are weak. (Ratio to Fe is
lt 0.010.1) gt The brightest neutral clump in the
GC region
Blue neutral Red plasma components
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Spectral fitting of the 6.4 keV clump
X-ray emission from the GC region (Koyama07,
Ryu09) 2 temp. plasma kT 1 keV
plasma (He, H-like Si, S, Ar, Ca) kT 7
keV plasma (He-, H-like Fe, Ni) neutral
clump (lines continuum)
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NH(ISM) 7.1(0.3)x1022cm-2 (Typical for
the GC sources)
S Ar Ca Cr Mn
kT1 0.99 0.02 keV kT2 7.02 0.33 keV
Z(Si) 1.3 0.1 solar Z(S,Ar,Ca) 1.6 0.1
Z(Fe/Ni) 1.2/2.1(fixed)
(Koyama07) He-like Cr, Mn lines are firstly
detected !!
neutral lines Fe-Ka, Kb, Ni-Ka continuum
NH(MC) 1.7 0.3 x1023
cm-2 G 1.85 0.15
These residuals correspond to neutral Ka line of
S, Ar, Ca, Cr, Mn.
(90 errors)
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Blue neutral Red plasma
Fe
Mn
S
Ar
Cr
Ca
Ni
without S, Ar, Ca, Cr, Mn lines
c2 355/208
c2 243/203
with S, Ar, Ca, Cr, Mn lines
7/11
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Discovery of neutral S, Ar, Ca, Cr, Mn lines
Observed line intensity graph
90 errors
Observed Line intensity
S Ar Ca Cr Mn Fe Ni
Element S Ar Ca Cr Mn Fe Ni
Significance (s) 3.5 3.2 8.1 4.5 4.6 85 5.7
We successfully detected fluorescence Ka lines of
these elements from the GC.
8/11
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Origin of the neutral lines X-ray/Electron
Neutral line neutral atoms must be ionized
by external X-rays / electrons. Continuum
Thomson scattering (X-ray) Bremsstrahlung
(electron)
Line emission
External X-ray / electron
molecular cloud NH 1023 cm-2
Continuum
Assumptions uniform density of the MC
solar abundance index of 2 (X-ray) / 3
(electron) lt observed photon index of 2
Different processes would make different
spectra. gt We calculated the spectra with Geant4
Equivalent width is a key to distinguish the two
scenarios
9/11
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Equivalent width and the origin
X-ray origin
Preliminary
This result may suggest the X-ray origin.
electron origin
90 errors
Calculated EWs depend on metal abundances,
geometry, and energy index of incident radiations
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Summary

• We successfully detected fluorescence K-shell
  lines from S, Ar, Ca, Cr, Mn from the brightest
  neutral clump of the Galactic center.
• Equivalent Widths of the neutral lines would
  suggest the X-ray origin rather than the electron
  origin.

Suzaku (4Msec) Red 0.5-2 keV Green 2-5
keV Blue 5-8 keV
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