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Stellar Feedback and Galaxy Evolution

Stellar Feedback and Galaxy Evolution. Q. Daniel Wang University of Massachusetts. IRAC 8 micro K-band ACIS diffuse 0.5-2 keV. Galaxy formation and evolution context. Toft et al. (2002); Muller & Bullock (2004). The missing baryon problem.

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Stellar Feedback and Galaxy Evolution

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  1. Stellar Feedback and Galaxy Evolution Q. Daniel Wang University of Massachusetts IRAC 8 micro K-band ACIS diffuse 0.5-2 keV

  2. Galaxy formation and evolution context Toft et al. (2002); Muller & Bullock (2004)

  3. The missing baryon problem • Observed baryon mass in stars and the ISM accounts for 1/3-1/2 of what is 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. Forms of the galactic feedback • AGNs (jets) • Nuclear starbursts or superwinds • Gradual energy inputs • Galactic disks: massive star formation • Galactic bulges: Type Ia SNe.

  5. AGN feedback • Centaurus A: • D=3.5 Mpc • Nearest radio-bright AGN • Lx(AGN) ~ 1042 erg/s • Lx(diffuse) ~ 5x1038 erg/s • The total mechanical energy output is not clear. • Most nearby galaxies do not contain AGNs! Karovska et al. 2002

  6. Starburst feedback optical 0.5-2 keV 2-8 keV Starbursts typically occur in low-mass gas-rich galaxies in the present Universe.

  7. Feedback in normal galaxies: our Galaxy 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

  8. X-ray absorption line spectroscopy 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

  9. Fe XVII K LMXB X1820-303 In the 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

  10. X-ray absorption line spectroscopy along the X1820-303 sightline: Results • Hot gas accounts for ~ 6% of the total O column density • Mean temperature T = 106.34 K • O abundance: • 0.3 (0.2-0.6) solar in neutral atomic gas • 2.0 (0.8-3.6) solar in ionized gas • Hot Ne/O =1.4(0.9-2.1) solar (90% confidence) • Hot Fe/Ne = 0.9(0.4-2.0) solar • Velocity dispersion 255 (165–369) km/s

  11. 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

  12. Galactic global hot gas properties • Non-isothermal: • 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 • Consistent with solar abundance ratios • 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 • But a large-scale hot halo is required to explain HVCs: confinement and OVI line absorption!

  13. 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 • Lx(diffuse) ~ 4x1039 erg/s • T1 ~ 106.3 K, T2> 107.1 K • Scale height ~ 2 kpc + more distant blubs. Li et al. (2008) NGC 5775

  14. M83 Soria & Wu (2002)

  15. Li et al. 2007

  16. 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

  17. 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? Galaxy Vc NGC 4565 250 NGC 2613 304 NGC 5746 307 NGC 2841 317 NGC 4594 370 Simulations by Toft et al. (2003)

  18. 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 2007

  19. 1-D Simulations of galaxy formation with the stellar feedback z=1.4 • Both dark and baryon matters evolve (with the final mass 1012 Msun) • A blastwave is initiated by the SB (forming a 5x1010 Msun bulge)and maintained by the Type Ia SN feedback. • The IGM is heated beyond the virial radius • The accretion can be stopped and the shocked hot gas expands • The resultant low density allows the bulge wind. • The wind can be shocked at a large radius. z=0.5 z=0

  20. 1-D Simulations of galaxy formation with the stellar feedback z=1.4 z=0.5 • If the specific energy of the feedback is reduced (e.g., because of mass-loading of the bulge wind), the wind has then evolved into a subsonic outflow. • This outflow can be stable and long-lasting • Consistent with observations of low Lx/LB galaxies (relative higher Lx, lower T, and more extended than those predicted by a supersonic wind. z=0

  21. Total baryon before the SB Cosmological baryon fraction Total baryon at present Hot gas Evolution of Baryons around galaxies • Galaxies such as the MW evolves in a hot bubble with a deficit of baryon matter • This bubble explains the lack of large-scale X-ray halos. • Bulge wind removes the present stellar feedback. • Results are sensitive to the initial burst and to the bulge/halo mass ratio

  22. 2-D simulations of galactic flows in M31 SNu=0.06 SNu=0.12 An ellipsoid bulge (q=0.6), a disk, and an NFW halo

  23. 3-D simulations of a galactic bulge wind • Energy not dissipated locally • Most of the energy is in the bulk motion and in waves • 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

  24. Conclusions • Diffuse X-ray-emitting gas is strongly concentrated toward galactic disks and bulges (< 20 kpc). • Heating is mostly due to SNe. But the bulk of their energy is not detected in X-ray near galactic bulges/disks and is probably propagated into the halos. • Feedback from a galactic bulge likely plays a key role in galaxy evolution: • Initial burst  heating and expansion of gas beyond the virial radius • Ongoing Type Ia SNe  keeping the gas from forming a cooling flow • Low n and high T are characteristics of the gaseous halos • Mass-loaded subsonic outflows account for diffuse X-ray emission from galactic bulges

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