IRAC 8 microK-band0.5-2 keV
X-ray Emission Line Spectroscopy of Diffuse Hot
Plasma
XMM-Newton RGSLiu, Wang, Li, & Peterson 2010
Li & Wan 2007
T ~ 3 x 106 K
Lx~2x1038 erg/s
Chandra ACIS-I
X-ray spectroscopy: He-like ions
• R (or W): Resonance line (allowed)
1s2p 1P11s2 1S0
electronic dipole transition
• I (or x+y): Intercombination line
1s2p 3P1 1s2 1S0 (y) 1s2p 3P2 1s2 1S0 (x) Triple or quadruplet
• F (or z): Forbidden line
1s2s 3S1 1s2 1S0
relativistic magnetic dipole transition (Aji
very low)
Simplified Grotrian diagram
Porquet & Dubau (2000)
RI
F
Photo-ionized plasma as seen in an AGN can have stronger forbidden lines.
Solar Wind Charge Exchange
From Dennerl 2010
Solar Wind Charge Exchange
• Charge exchange (CX) nature of comet X-ray emission is confirmed, spectroscopically and temporally.
• CX has a cross-section of ~10-
15 cm-2
• PCX/Pth propto 1/ne2 on scales of
mean free path
Peter Beiersdorfer
CX is also expected at the heliosphere
Much of the diffuse soft X-ray background may arise from the CX!
ROSAT all-sky survey in the ¾-keV
band
X-ray binaryAGN Futamoto et al. 2004, Wang et al. 05,
Yao & Wang 05/06, Yao et al. 06/07/08
4U1957+11
X-ray absorption line spectroscopy of diffuse hot plasma
Fe XVII K
• Tracing all K transitions of metals all three phases of the ISM.
• Not affected by photo-electric absorption unbiased measurements of the global ISM.
Yao & Wang 2006, Yao et al. 2006, Futamoto et al 2004
LETG+HETG spectrum of LMXB 1820-303
Chandra ACIS observations of nearby galaxies
Soria & Wu (2002) (Credit: NASA/CXC/SAO/R.DiStefano et al.)
XMM-Newton RGS spectrum of the nuclear starburst region of M51
Charge exchange may be responsible for much of diffuse soft X-ray emission in both normal and starburst galaxies.
Similar CX signatures are also observed in starburst galaxies
Soft X-ray arises primarily from the interplay between a superwind and entrained cool gas clouds.
Composite of optical (HST), infrared (Spitzer), and X-ray (Chandra) images
Li, Mao, Wang 2011
XMM-Newton Reflection Grating Spectrometers
Spatially-resolved X-ray spectroscopy
OVIII contours on HST image
OVIII contours on OVII image
NGC 4438 in the Virgo Cluster
Ha+[NII] image (Kenney et al. 1995). Chandra 0.3-2 keV image, Machacek et al. 2004
Operating X-ray Telescopes
SWIFT
Chandra
Suzaku
XMM-Newton
Future X-ray telescopes
Astro-H, planned for launch in 2013
eROSITA 2012
Athena???
Summary• X-ray spectroscopy is the future of the X-
ray astronomy X-ray astrophysics, providing key diagnostics of plasma in the Universe.
• Much of the diffuse X-ray emission from galaxies may arise from the charge exchange.
• A lot can already be done to understand the process, which traces the galactic feedback and the presence of cool gas, especially in low density environments.