discovery of k lines of neutral sulfur, argon, and calcium atoms from the galactic center masayoshi...
TRANSCRIPT
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
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 (NH~1024 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 source1E 1743.1-2843
20’ (50 pc)
Sgr B2Radio Arc
Fe=1
Ni
Mn
S
ArCa
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
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)
selectedregion20 arcmin
Neutral Fe
He, H-like lines;mainly due to plasma
Si S Ar
Ca
Fe
Blue: neutralRed: plasma components
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)
x x
Add He-like Cr, Mn lines(APEC does not contain)
kT1 = 0.99 ± 0.02 keVkT2 = 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-Kcontinuum: NH(MC) = 1.7 ± 0.3 x1023 cm-2
= 1.85 ± 0.15
NH(ISM) =7.1(±0.3)x1022cm-2 (Typical for the GC) S Ar Ca Cr Mn
These residuals correspond to neutral S, Ar, Ca, Cr, Mn.
(90% errors)
S ArCa Cr
Mn
Fe
Ni
without S, Ar, Ca, Cr, Mn lines
with S, Ar,Ca, Cr, Mnlines 7/11
2 = 243/203
2 = 355/208
Blue: neutralRed: plasma
Element S Ar Ca Cr Mn Fe Ni
Significance ()
3.5 3.2 8.1 4.5 4.6 85 5.7
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
Obs
erve
d Li
ne in
tens
ity
What is the origin of the neutral lines ?
molecular cloudNH = 1023 cm-2
Line emission
Injection ofX-ray / electron
Line: Ionization of neutral atoms by injected X-rays / electrons.Continuum: Thomson scattering (X-ray) Bremsstrahlung (electron)
Fe
Fe
Ar
S
CaCr
Mn
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
10/11
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 Geant4Assumed solar abundance
90% errors
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