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What is getting in and/or out of nearby disk galaxies?

What is getting in and/or out of nearby disk galaxies?. Q. Daniel Wang University of Massachusetts. The galaxy evolution context. The “overcooling” problem: T oo much condensation to be consistent with observations. Toft et al. (2002); Muller & Bullock (2004).

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What is getting in and/or out of nearby disk galaxies?

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  1. What is getting in and/or out of nearby disk galaxies? Q. Daniel Wang University of Massachusetts

  2. The galaxy evolution context • The “overcooling” problem: • Too much condensation to be consistent with observations Toft et al. (2002); Muller & Bullock (2004)

  3. ROSAT X-ray All-sky ¾-keV Diffuse Background Map X-ray binary ~50% of the background is thermal and local (z < 0.01) The rest is mostly from AGNs (McCammon et al. 2002)

  4. New Tool: Chandra • CCD: • Resolution res. ~ 1” • Spectral Res. E/E ~ 20 • Grating: • Spectral Res. ~ 500 km/s

  5. Absorption Sight Lines X-ray binary AGN ROSAT all-sky survey in the ¾-keV band X-ray binary

  6. Fe XVII K LMXB X1820-303 • In GC NGC 6624 • l, b = 2o.8, -8o • Distance = 7.6kpc 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 LETG+HETG spectrum Yao & Wang 2006, Yao et al. 2006

  7. OVII OVIII Ne IX Ne VIII OVI Ne X 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

  8. X1820-303: Results • Hot gas accounts for ~ 6% of the total O column density • O abundance: • 0.3 (0.2-0.6) solar in neutral atomic gas • 2.0 (0.8-3.6) solar in ionized gas • Ne/O =1.4(0.9-2.1) solar (90% confidence) • Fe/Ne = 0.9(0.4-2.0) solar • Filling factor (relative to total ionized gas): ~0.95, if ph ~ pw ~0.8, if ph ~ 5pw as in the solar neighborhood • Mean temperature LogT(k) = 6.34 (6.29-6.41) • Velocity dispersion 255 (165–369) km/s

  9. Mrk 421 (Yao & Wang 2006) • Joint-fit with the absorption lines with the OVII and OVIII line emission data from McCammon et al. (2002) • n=n0e-z/hn; T=T0e-z/hT •  n=n0(T/T0), =hT/hn, L=hn/sin b OVI 1032 A

  10. LMC X-3 as a distance marker • BH X-ray binary, typically in a high/soft state • Roche lobe accretion • 50 kpc away • Vs = +310 km/s • Away from the LMC main body Wang et al. 2005 H image

  11. Ne IX OVII LMC X-3: absorption lines The EWs are about the same as those seen in AGN spectra!

  12. Global distribution models Combining all the sight lines together: • Disk model nH = 5.0x10-3 cm-3 exp[-|z|/1.1 kpc] Total NH~1.6 x1019 cm-2 • Sphere model nH = 6.1x10-2 cm-3 exp[-R/2.7 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 X-ray absorption is primarily around the Galactic disk and the bulge within a few kpc! Yao & Wang (2005)

  13. Global hot gas properties • Non-isothermal: • mean T ~ 106.3 K toward the inner region • ~ 106.1 K at solar neighborhood • Consistent with solar abundance ratios • Velocity dispersion from ~200 km/s to 80 km/s • A thick Galactic disk with a scale height 1-2 kpc, ~ the values of OVI absorbers and free electrons • No significant X-ray absorption beyond the LMC (~< 1019 cm-2, assuming the solar abundance) But a large-scale gaseous halo required for • The confinement of HVCs • Ram-pressure stripping • Interfaces at intermediate T

  14. NGC 3556 (Sc) • Active star forming • Hot gas scale height ~ 2 kpc • Lx ~ 1% of SN energy Red – optical Green – 0.3-1.5 keV band Blue – 1.5-7 keV band Wang et al. 2004

  15. NGC 2841 (Sb) • D=15 Mpc • Low SF rate • Lx ~ 7 x 1039 ergs/s Red: optical Blue: 0.3-1.5 keV diffuse emission Wang 2006

  16. Wang (2006) 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)

  17. NGC 4594 (Sa) Red: near-IR Green: 0.3-1.5 keV Blue: 1.5-7 keV H ring Li et al. 2006

  18. NGC 4631 NGC 4594 Point source • 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 from evolving stars ~ 1.3 Msun/yr • Each Type Ia SN  0.7 Msun Fe disk Outer bulge Inner bulge

  19. XMM/Newton observation of NGC 2613 (Sb, D=26 Mpc, Vc=304 km/s) Toft et al. Stellar light 0.5-2 keV band; Li et al. (2006) Similar results from NGC 5746 (Vc=250 km/s, Petersen et al. 2005)

  20. Extraplanar hot gas seen in nearby galaxies • 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 • No evidence for large-scale X-ray-emitting galactic halos

  21. Observations vs. simulations • Little evidence for X-ray emission or absorption from IGM accretion. No “overcooling” problem? • Missing stellar energy feedback, at least in early-type spirals. Where does the energy go? NGC 2613 NGC 4594 NGC 4565 Toft et al. (2003)

  22. Galactic bulge simulation • Parallel, adaptive mesh refinement FLASH code • Finest refinement in one octant down to 6 pc • Stellar mass injection and SNe, following stellar light • SN rate ~ 4x10-4 /yr • Mass injection rate ~0.1 Msun/yr) 10x10x10 kpc3 box density distribution

  23. Galactic bulge simulation • Parallel, adaptive mesh refinement FLASH code • Finest refinement in one octant down to 6 pc • Stellar mass injection and SNe, following stellar light • SN rate ~ 4x10-4 /yr • Mass injection rate ~0.03 Msun/yr) 3x3x3 kpc3 box density distribution

  24. Galactic bulge simulation: • Ejecta dominate the high-T emission • Not well-mixed with the ambient medium • Probably cool too fast to be mixed with the medium SN ejecta

  25. High Res. 1-D Low Res. Log(T(K)) Comparison with the 1-D solution • The average radial density and temperature distributions are similar to the 1-D model. • Large dispersion, particularly in the hot Fe distribution • enhanced emission at both low and high temperatures

  26. Where is the energy? • Radiative cooling is not important in the bulge region, consistent with the observation • Energy not dissipated locally • Most of the energy is in the bulk motion and in waves

  27. The fate of the energy • Maybe eventually damped by cooling gas in the galactic hot halo. • Galactic wind not necessary, depending the galaxy mass and IGM environment. • Interaction with the infalling IGM  a possible solution to the over-cooling problem. kpc

  28. Conclusions and Speculations • Diffuse X-ray-emitting gas is strongly concentrated toward galactic disks and bulges. No evidence for large-scale halos on scales > ~ 20 kpc. • Heating is most likely due to SNe. But the bulk of the SN energy is not detected and is probably propagated into the halo, balancing the cooling. • Thermal and metallicity inhomogneities in the IGM naturally lead to its selective cooling • High velocity clouds  OVI absorbers, etc. • Low metallicity and high T  the radiatively inefficient hot halo.

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