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Summary: Galactic hot ISM. No significant X-ray absorption beyond the LMC (~< 10 19 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

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summary galactic hot ism
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
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

ngc 2841 sb
NGC 2841 (Sb)

Red: optical

Blue: 0.3-1.5 keV diffuse emission

ngc 4565 sb
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 4594 sa
NGC 4594 (Sa)

H ring

Red: optical

Green: 0.3-1.5 keV

Blue: 1.5-7 keV

ngc 4594 x ray spectra
NGC 4631NGC 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, or ~ 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

Inner bulge

galaxy formation simulations vs observations
Galaxy formation simulations vs. observations

NGC 4594

NGC 4565

NGC 4594

NGC 4565

Toft et al. (2003)

summary nearby galaxies
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?

feedback
Feedback
  • Radiation
  • AGNs
  • Supernovae
    • Core-collapsed SNe
    • Type 1a
bulge wind model
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 2006

data vs model
Data vs model

Consistent with the expected total mass loss and SN rates as well as the Fe abundance of ~ 4 x solar!

3 d hydro simulations
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
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

rosat x ray all sky survey
ROSAT X-ray All-sky Survey

Red – 1/4 keV band

Green – 3/4 keV band

Blue – 1.5 keV band

conclusions and implications
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
galactic bulge simulation fe
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
Non-uniformity effects

High Res.

1-D

Low Res.

1-D

Log(T(K))

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