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Stellar Feedback and Evolution of Milky Way-like Galaxies

Stellar Feedback and Evolution of Milky Way-like Galaxies. Q. Daniel Wang University of Massachusetts, Amherst. IRAC 8 micro K-band ACIS diffuse 0.5-2 keV. Galaxy formation and evolution context. Toft et al. (2002). The “overcooling” problem:

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Stellar Feedback and Evolution of Milky Way-like Galaxies

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  1. Stellar Feedback and Evolutionof Milky Way-like Galaxies Q. Daniel Wang University of Massachusetts, Amherst IRAC 8 micro K-band ACIS diffuse 0.5-2 keV

  2. Galaxy formation and evolution context Toft et al. (2002) • The “overcooling” problem: • Too much condensation to be consistent with observations (e.g., White & Rees 1978; Navarro & Steinmetz 1997)

  3. The “missing” baryon problem • Stars and the ISM accounts for 1/3-1/2 of the baryon expected from the gravitational mass of a galaxy. • Where is the remaining baryon matter? • In a hot gaseous galactic halo? • Or having been pushed away? • Both are related to the galactic energy feedback!

  4. Origins of the galactic feedback • AGNs (jets) • Nuclear starbursts: • Radiation pressure • Superwinds • Gradual energy inputs • Galactic disks: massive star formation • Galactic bulges: Type Ia SNe.

  5. X-ray imaging of nearby “normal” galaxies • Hydro-simulations of stellar feedback and galaxy evolution. Outline • X-ray absorption line spectroscopy of hot gas in and around the MW.

  6. Pre-Chandra View of the hot gas ROSAT ¾-keV Diffuse Background Map: ~50% of the background is thermal and local (z < 0.01) The rest is mostly from faint AGNs (McCammon et al. 2002) X-ray binary

  7. X-ray absorption line spectroscopy:adding depth into the map 4U1957+11 X-ray binary AGN Wang et al. 05, Yao & Wang 05/06, Yao et al. 06/07 ROSAT all-sky survey in the ¾-keV band X-ray binary

  8. Fe XVII K X-ray absorption line spectroscopy is powerful ! • Tracing all K transitions of metals  all three phases of the ISM. • Not affected by photo-electric absorption unbiased measurements of the global ISM. LETG+HETG spectrum of LMXB X1820-303 Yao & Wang 2006, Yao et al. 2006, Futamoto et al 2004

  9. OVII OVIII Ne IX Ne VIII OVI Ne X Spectroscopic diagnostics One line (e.g., OVII K)  velocity centroid and EW  constraints on the column density, depending on assumed b and T Two lines of different ionization states (OVII and OVIII K)  T Two lines of the same state (K and K)  b Lines from different species  abundance fa Assuming solar abundances and CIE Yao & Wang 2005

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

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

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

  13. Galactic global hot gas properties • Structure: • A thick Galactic disk with a scale height 1-2 kpc, ~ the values of OVI absorbers and free electrons • Enhanced hot gas around the Galactic bulge • No evidence for a large-scale (r ~ 102 kpc) X-ray-emitting/absorbing halo with an upper limit of NH~1 x1019 cm-2 • Thermal property: • mean T ~ 106.3 K toward the inner region • ~ 106.1 K at solar neighborhood • Velocity dispersion from ~200 km/s to 80 km/s • Abundance ratios consistent with solar

  14. But a large-scale hot gaseous halo is required to explain HVCs!

  15. Feedback from disk-wide star formation Diffuse X-ray emission compared with HST/ACS images: Red – H Green – Optical R-band Blue – 0.3-1.5 keV • Scale height ~ 2 kpc + more distant blubs. • Lx(diffuse) ~ 4x1039 erg/s • T1 ~ 106.3 K, T2> 107.1 K Li, J. et al. (2008) NGC 5775

  16. M83 Soria & Wu (2002) Much work is yet to be done to determine the differential properties of the hot gas.

  17. IRAC 8 micro K-band 0.5-2 keV M31 Li & Wang 2007 0.5-1 keV 1-2 keV 2-8 keV Lx~2x1038 erg/s, only ~1% of the Type Ia SN energy input

  18. Mass-loading from the nuclear spiral? • SMBH is not active • No SF in the bulge • Photo-ionization probably due to PAGB stars • Correlation of diffuse X-ray with the H emission  evaporation via thermal conduction? H image with 0.5-2 keV contours

  19. NGC 4594 (Sa) • Average T ~ 6 x 106 K • Lx ~ 4 x 1039 erg/s, ~ 2% of Type Ia SN energy • Not much cool gas to hide/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 Li et al. 2007

  20. Summary for 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, although a possible very hot component (T > 107 K) is poorly constrained.

  21. Observations vs. simulations Little evidence for X-ray emission or absorption from IGM accretion. No “overcooling” problem? Galaxy Vc NGC 4565 250 NGC 2613 304 NGC 5746 307 NGC 2841 317 NGC 4594 370 Simulations by Toft et al. (2003)

  22. The missing energy and large LX/LK dispersion problems of low-mass ellipticals David et al (2006) • Observed LX is < 10% of the energy inputs. • Galactic wind model fails: • Predict too small LX with little dispersion • Too high T, fixed by the specific energy input • Too steep radial surface intensity profile. SNe AGN

  23. Problems with the existing models • Model of the stellar feedback • Typically with no consideration of the evolving galactic environment • Fixed outer boundary  unstable subsonic solution • No additional mass-loading • Model of galaxy evolution via IGM accretion • Typically with no stellar feedback (e.g., BirnBoim, Dekel, & Neistein 07) • Predicted massive cooling hot gaseous halos are not observed. • But a large-scale, low-density hot gaseous halo is required to explain HVCs around the MW.

  24. 1-D Simulations of galaxy formation with the stellar feedback • Evolution of both dark and baryon matters (with the final mass 1012 Msun) • Initial bulge formation (5x1010 Msun)  starburst  shock-heating and expanding of gas • Later Type Ia SNe  bulge wind/outflow, maintaining a low-density high-T halo, preventing a cooling flow Tang, Wang, Lu, & Mo 2008

  25. 1-D Simulations of galaxy formation with the stellar feedback z=1.4 • A blastwave, initiated by the SB, is maintained by the Type Ia SN feedback. • The IGM is heated beyond the virial radius. • The accretion can be stopped. • The bulge wind can be shocked at a large radius. z=0.5 z=0

  26. Dependence on the specific energy of the feedback z=1.4 z=0.5 • If the mass-loading is important, the wind may then have evolved into a subsonic outflow. • This outflow can be stable and long-lasting  higher Lx, lower T, and more extended profile. • Consistent with observations! z=0

  27. Total baryon before the SB Cosmological baryon fraction Total baryon at present Hot gas Galaxies such as the MW evolve in hot bubbles of baryon deficit! • Explains the lack of large-scale X-ray halos. • Bulge wind drives away the present stellar feedback.

  28. 2-D simulations of the feedback in M31 • Qualitatively consistent with the 1-D results • Instabilities at the contact discontinuities  formation of HVCs? An ellipsoid bulge (q=0.6), a disk, and an NFW halo Tang & Wang (2008)

  29. 3-D simulations of a galactic bulge wind • Adaptive mesh refinement, down to 6 pc • Stellar mass injection and sporadic SNe, following the stellar light. 10x10x10 kpc3 box density distribution

  30. Emission primarily from shells and filaments. • Fe-rich ejecta dominate the high-T emission • Not well-mixed with the ambient medium

  31. 1-D Low Res. Log(T(K)) 3-D Effects • Large dispersion  • enhanced emission at both low and high temperatures • Overall luminosity increase by a factor of ~ 3. • Low metallicity if modeled with a 1-T plasma. • Consistent with the 1-D radial density and temperature distributions, except for the center region. 1-D

  32. Conclusions • Diffuse hot gas is strongly concentrated toward galactic disks/bulges (< 20 kpc) due to the feedback. • But the bulk of the feedback is not detected and is probably propagated into very hot (~107 K) halos. • The feedback from a galactic bulge likely plays a key role in galaxy evolution: • Initial burst led to the heating and expansion of gas beyond the virial radius • Ongoing feedback keeps the gas from forming a cooling flow and starves SMBHs • Mass-loaded outflows account for diffuse X-ray emission from galactic bulges. • Galaxies like ours reside in hot bubbles! • No overcooling or missing energy problem!

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