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Sun. What do we know about the HISM?. For a review, see D. Cox (2005, ARAA). ROSAT X-ray All-sky Survey. Red – 1/4 keV band Green – 3/4 keV band Blue – 1.5 keV band. ~50% of the ¾-keV background is thermal and local (z < 0.01); rest is mostly from AGNs McCammon et al. 2002.
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Sun What do we know about the HISM? For a review, see D. Cox (2005, ARAA)
ROSAT X-ray All-sky Survey Red – 1/4 keV band Green – 3/4 keV band Blue – 1.5 keV band ~50% of the ¾-keV background is thermal and local (z < 0.01); rest is mostly from AGNs McCammon et al. 2002
What we do not know: • Overall spatial distribution • Filling factor • Physical and chemical states • Kinematics • Heating, transporting, and cooling • Effects on galaxy formation and evolution
New Tool: Chandra • CCD • resolution res. ~ 1” • Spectral Res. E/E ~ 20 • Grating • Spectral Res. ~ 500 km/s
Absorption spectroscopy: Add the depth Measure the column density, thus the mass Direct line diagnostics Independent of cool gas absorption External views: Global properties Relationship between various components Dependence on galaxy properties and environment The Global Hot ISM: New Perspectives • Modeling of the SN-dominated hot ISM • 1-D galactic bulge wind • 3-D simulations
Mrk 421;Nicastro et al. 2005 Detection of X-ray absorption lines:
3C 273 Mkn 421 Where is the absorbing gas located? LETG/HRC LETG/ACIS Wang & Yao 2005
LMC X-3 as a distance marker • BH X-ray binary, typically in a high/soft state • Roche lobe accretion • 50 kpc away • +310 km/s • Away from the LMC main body H image
Obs. Of LMC X-3 • Chandra LETG: 100 ks. • FUSE: 100 ks • RXTE: 100 ks Wang et al. 2005
Ne IX OVII LMC X-3: absorption lines The EWs are about the same as those seen in AGN spectra!
OVII OVIII Ne IX Ne VIII OVI Ne IX Absorption line diagnostics I()=Ic() exp[-()] ()NHfafi(T)flu(,0,b) b=(2kT/mi+2)1/2 accounting for line saturation and multiple line detections Assuming CIE and solar abundances Yao & Wang 2005
Results from extragalactic sources No evidence for significant X-ray absorption beyond the LMC!!!
LMXB 4U 1820-303:A Galactic distance marker • In GC NGC 6624 • Distance = 7.6; l, b = 2o.8, -8o tracing the global ISM • 1 kpc away from the Galactic plane NHI • Two radio pulsars in the GC DM Ne • Chandra observations: • 15 ks LETG (Futamoto et al. 2004) • 21 ks HETG Yao & Wang 2005
4U 1820-303: Results • Hot gas accounts for ~ 6% of the total O column density • O abundance: • 2.0 (0.8-3.6) solar in ionized gas • 0.3 (0.2-0.6) solar in neutral atomic gas. • Ne/O =1.4(0.9-2.1) solar • Filling factor (relative to total ionized gas): ~0.95, if ph ~ pw ~0.8, if ph ~ 5pw as in the solar neighborhood • LogT(k) = 6.34 (6.29-6.41) • Velocity dispersion 255 (165–369) km/s
Temperature Dist. d NH(T) = TdlogT
More Sources Global HISM distribution • LMXBs with |b| > 2o • S/N > 7 per bin at ~0.6 keV • Excluding sources with identified intrinsic emission/absorption features • Ten LMXBs with 17 observations (6 with the LETG) Yao & Wang 2005
Absorption Sight Lines AGN X-ray binary No detection ROSAT all-sky survey in the ¾-keV band
Global distribution models • Sphere model • nH = 6.1(-3.0,+3.6)x10-2 cm-3 exp[-R/2.7(-0.4,+0.8) kpc] ~3 x 10-3 cm-3 at the Sun • Total NH~6.1 x1019 cm-2 • MH~7.5(2.5-16)x108 Msun • Disk model • nH = 5.0(-1.8,+2.6)x10-3 cm-3 exp[-|z|/1.1(-0.5,+0.7) kpc] • Total NH~1.6 x1019 cm-2 X-ray absorption is primarily around the Galactic disk within a few kpc!
Summary: Galactic hot ISM • No significant X-ray absorption beyond the LMC (~< 1019 cm-2, assuming the solar abundance) • A thick Galactic disk with a scale height 1-2 kpc, ~ the values of OVI absorbers and free electrons • O abundance ~ solar or higher • Mean T ~ 106.3+-0.2 K, ~ 106.1 K at solar neighborhood • Large nonthermal v dispersion, especially at the GC • High volume filling factor (> 0.8) within |z| < 1 kpc
External Perspective: NGC 3556 (Sc) • Active star forming • Hot gas scale height ~ 2 kpc • Lx ~ 1% of SN mech. Energy input Red – optical Green – 0.3-1.5 keV band Blue – 1.5-7 keV band Wang et al. 2004
Wang (2004) Red – optical Green – 0.3-1.5 keV band Blue – 1.5-7 keV band NGC 4565 (Sb) Very low specific SFR No sign for any outflows from the disk in radio and optical William McLaughlin (ARGO Cooperative Observatory)
NGC 2841 (Sb) Red: optical Blue: 0.3-1.5 keV diffuse emission
NGC 4594 (Sa) H ring Red: optical Green: 0.3-1.5 keV Blue: 1.5-7 keV
NGC 4631 NGC 4594:X-ray spectra Point source disk Outer bulge • Average T ~ 6 x 106 K • Strong Fe –L complex • Lx ~ 4 x 1039 erg/s Inner bulge
Missing stellar feedback in early-type disk galaxies • For NGC 4594, hot gas radiative cooling rate ~ 2% of the energy input from Type Ia SNe alone • Not much cool gas to hide or convert the SN energy • Mass and metals are also missing! • Mass input rate of evolved stars ~ 1.3 Msun/yr • Each Type Ia SN 0.7 Msun Fe
Galaxy formation simulations vs. observations NGC 4594 NGC 4565 NGC 4594 NGC 4565 Toft et al. (2003)
Summary: Nearby galaxies • Good News • At least two components of diffuse hot gas: • Disk – driven by massive star formation • Bulge – heated primarily by Type-Ia SNe • Characteristic extent and temperature similar to the Galactic values • Bad news • Missing stellar feedback, at least in early-type spirals. • Little evidence for X-ray emission or absorption from IGM accretion --- maybe good news for solving the over-cooling problem. Are these problems related?
Bulge wind model • Spherical, steady, and adiabatic • NFW Dark matter halo + stellar bulge • Energy and mass input follows the stellar light distribution • CIE plasma emission • Implemented in XSPEC for both projected spectral and radial surface brightness analyses Li & Wang 2005
Data vs model Consistent with the expected total mass loss and SN rates as well as the Fe abundance of ~ 4 x solar!
The best-fit model density and temperature profiles of the bulge wind
3-D hydro simulations • Goals • To characterize the density, temperature, and metal abundance structures, the heating and cooling processes, and the kinematics of the HISM • To calibrate the 1-D model • Hydro simulations with metal particle tracers • Parallel, adaptive mesh refinement FLASH code • Whole galactic bulge simulation with the finest refinement in one octant down to 6 pc • Stellar mass injection and SNe, following stellar light • Realistic gravitational potential of the bulge and the dark matter halo
Galactic bulge simulation: density • 3x3x3 kpc3 box • SN rate ~ 4x10-4 /yr • Mass injection rate ~0.03 Msun/yr • Logarithmic scale • Statistical steady state • ~ adiabatic Tang et al. 2005
Galactic bulge simulation: Fe • Fe-rich ejecta dominate the high-T emission • Not well-mixed with the ambient medium • May cool too fast to be mixed with the global hot ISM
Non-uniformity effects High Res. 1-D Low Res. 1-D Log(T(K))
Conclusions and implications • Large inhomogeneity is expected • particularly in the hot Fe distribution • enhanced emission at both low and high temperatures (compared to the 1-D solution) • SNe generate waves in the HISM • Energy not dissipated locally or in swept-up shells • Maybe eventually damped by cool gas or in the galactic hot halo • Galactic wind not necessary • Possible solution to the over-cooling problem of galaxy formation
Acknowledgement • Absorption line studies • Y. Yao, T. Tripp, T.-T. Fang, … • X-ray imaging of nearby galaxies • T. Chevas, J. Irwin, Z. Li… • 1-D and 3-D model and simulations • Z. Li, S. Tang, M. Mac Low
Comparison with X-ray emission Disk dist. Uniform dist. Observed
Consistency check: timescales Radiative cooling O recom. T/(dT/dt) Fe recom.
Chandra Grating Instrument Properties FWHM ~ 5x102 km/s
Sample of normal disk galaxies All with low Galactic foreground absorption (NH < 3 x 1020 cm-2)