Discovery of K  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 K  lines of S, Ar, Ca, Cr, Mn What is the origin of the neutral lines ? Summary 1/11 Galactic center workshop 2009, shanghai, hope hotel

Neutral Fe line emission from the GC region 2/11 Molecular gas CS (J=1-0) 6.4 keV (neutral Fe-K  ) emission shows a clumpy distribution in the Galactic center region. Neutral clumps are correlated with giant molecular clouds (Sgr B2, Radio Arc regions…) Spectrum of Sgr B2 ・ prominent neutral Fe line ・ strongly absorbed continuum (N H ~10 24 cm -2 ) Energy (keV) Sgr B2 Neutral iron line Sgr B2 Radio Arc 6.4 keV map Sgr B2 Sgr B1 M G Sgr A East (SNR) X-ray binary 1E ’ (50 pc) Sgr B2 Radio Arc

Fe=1 Ni Mn S Ar Ca Cr *solar abundance Other neutral lines ? Lighter elements, S, Ar, Ca, Cr, Mn are expected to exist in the molecular cloud. We searched for the neutral lines from these elements using the Suzaku satellite. Low energy K-Shell lines are absorbed by an ISM. 3/11

The strongest neutral clump 4/11 Other neutral lines are weak. (Ratio to Fe is < 0.01—0.1) => The brightest neutral clump in the GC region Sgr B2 Radio Arc 6.4 keV map Sgr B2 Sgr B1 M G Sgr A East (SNR) selected region 20 arcmin Neutral Fe He, H-like lines mainly come from hot plasma Si S Ar Ca Fe Blue: neutral Red: plasma components

Spectral fitting of the 6.4 keV clump 5/11 X-ray emission from the GC region: (Koyama+07, Ryu+09) 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) Fitting model: 2 temp. plasmas (kT~1 keV + 7 KeV) neutral component (lines + continuum) Firstly, neutral lines; only Fe K , K  + Ni K  Abs (MC) Abs (ISM) xx We added He-like Cr, Mn lines (APEC does not contain)

kT 1 = 0.99 ± 0.02 keV kT 2 = 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) (Koyama+07) He-like Cr, Mn lines are firstly detected !! neutral lines: Fe-K , K , Ni-K  continuum: N H (MC) = 1.7 ± 0.3 x10 23 cm -2  = 1.85 ± 0.15 N H (ISM) =7.1(±0.3)x10 22 cm -2 (Typical for the GC sources) S Ar Ca Cr Mn These residuals correspond to neutral K  line of S, Ar, Ca, Cr, Mn. (90% errors)

SAr Ca Cr Mn Fe Ni without S, Ar, Ca, Cr, Mn lines with S, Ar, Ca, Cr, Mn lines 7/11  2 = 243/203  2 = 355/208 Blue: neutral Red: plasma

ElementSArCaCrMnFeNi Significance (  ) We successfully detected fluorescence K  lines of these elements from the GC. Observed line intensity graph Discovery of neutral S, Ar, Ca, Cr, Mn lines S Ar Ca Cr Mn Fe Ni 90% errors 8/11 Observed Line intensity

Origin of the neutral lines: X-ray/Electron molecular cloud N H = cm -2 Line emission External X-ray / electron Neutral line: neutral atoms must be ionized by external X-rays / electrons. Continuum: Thomson scattering (X-ray) Bremsstrahlung (electron) Fe Ar SCaCrMn 9/11 Continuum Different processes would make different spectra. => We calculated the spectra with Geant4 Assumptions: uniform density of the MC solar abundance index of 2 (X-ray) / 3 (electron) <= observed photon index of ~2 Equivalent width is a key to distinguish the two scenarios

10/11 Equivalent width and the origin X-ray origin electron origin This result may suggest the X-ray origin. 90% errors Preliminary *Calculated EWs depend on metal abundances, geometry, and energy index of incident radiations

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. 11/11 Suzaku (4Msec) Red: keV Green: 2-5 keV Blue: 5-8 keV

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