1. Discovery of K  lines of neutral sulfur, argon, and calcium atoms from the Galactic Center 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

2. Neutral Fe line emission from the GC 2/11 Molecular gas CS (J=1-0) 6.4 keV (neutral Fe-K  ) line shows a clumpy distribution in the Galactic center. 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 ) 3 4 5 6 7 8 Energy (keV) Sgr B2 Neutral iron line Sgr B2 Radio Arc 6.4 keV map Sgr B2 Sgr B1 M0.74-0.09 G0.174-0.233 Sgr A East (SNR) Bright source 1E 1743.1-2843 20’ (50 pc) Sgr B2 Radio Arc

3. 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. Let’s search for the neutral lines from the lighter elements !! Low energy K-Shell lines are absorbed by ISM. 3/11

4. 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 Sgr B2 Radio Arc 6.4 keV map Sgr B2 Sgr B1 M0.74-0.09 G0.174-0.233 Sgr A East (SNR) selected region 20 arcmin Neutral Fe He, H-like lines; mainly due to plasma Si S Ar Ca Fe Blue: neutral Red: plasma components

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

6. 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) S Ar Ca Cr Mn These residuals correspond to neutral S, Ar, Ca, Cr, Mn. (90% errors)

7. 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

8. ElementSArCaCrMnFeNi Significance (  ) 3.53.28.14.54.6855.7 Newly detected !! 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

9. What is the origin of the neutral lines ? molecular cloud N H = 10 23 cm -2 Line emission Injection of X-ray / electron Line: Ionization of neutral atoms by injected X-rays / electrons. Continuum: Thomson scattering (X-ray) Bremsstrahlung (electron) Fe Ar SCaCrMn 9/11 Continuum Different processes would make different spectra. => Equivalent width (EW) is a good indicator for the origin. Calculation of EWs by Geant4 Assumptions: uniform density of the MC solar abundance index of 2 (X-ray) / 3 (electron) <= observed spectral index of ~2

10. 10/11 S Ar Ca Cr Mn Fe Ni Equivalent width and the origin X-ray origin electron origin EWs of S—Ni would prefer the X-ray origin Preliminary Models are calculated by Geant4 Assumed solar abundance 90% errors

11. 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 X-ray origin rather than electron one. Thank you 11/11