Feedback Observations and Simulations of Elliptical Galaxies

1. Feedback Observations and Simulations of Elliptical Galaxies • Daniel Wang, Shikui Tang, Yu Lu, Houjun Mo (UMASS) • Mordecai Mac-Low (AMNH) • Ryan Joung (Princeton) • Zhiyuan Li (CfA) 3-D stellar feedback simulation NGC 4697: X-ray intensity contours

2. Key questions to address • Why do elliptical galaxies typically evolve passively?  Understanding the cause of the bi-modality of galaxies • What is the role of stellar feedback? • Mass loss from evolved stars: ~ 0.2 M☉/1010LB☉/yr • Energy input from Ia SNe with a rate ~ 0.2 /1010LB☉/100yr  Specific temperature:T ~ 1-2 Kev • Fe abundance ~Z*+5(MSN/0.7Msun) • traced by X-ray

3. Observations of stellar feedback • Large scattering of LX for galaxies with the same LB or LK • Observed Lx is <10% of the energy inputs • Mass of Diffuse gas ~ 106 – 107 M☉,can be replenished within 108 yrs. David et al (2006) SNe AGN

4. Humphrey & Buote (2006) O’Sullivan & Ponman (2004),Irwin et al (2001), Irwin (2008) Observations of stellar feedback Bregman et al (2004) • Both gas temperature and Fe abundance are much less than the expected.

5. Galactic wind? • The overall dynamic may be described by a 1-D wind model • But it is inconsistent with observations: • Too small Lx (by a factor > 10) with little dispersion • Too steep radial X-ray intensity profile • Too high Temperature, fixed by the specific energy input • Too high Fe abundance of hot gas • Can 3-D effects alleviate these discrepancies? • X-ray emission is sensitive to the structure in density, temperature, and metal distributions

6. Galactic wind: 3-D simulations • 5 x 1010 Msun spheroid • Adaptive mesh refinement, ~2 pc spatial resolution, using FLASH Hydrodynamic code • Continuous stellar mass injection and sporadic SNe • Initialized from established 1-D wind solution Tang et al 2009 Tang & Wang 2009 10x10x10 kpc3 BoxDensity snapshot

7. 3-D effects Differential Emission Measure • Broad density and temperature distributions • low metallicity if modeled with a 1- or 2-T plasma, even assuming uniform solar metallicity. • Overall luminosity increase by a factor of ~ 3.

8. Galactic wind model: limitation • A passive evolved galaxy inside a static halo • Gas-free initial condition Only reasonable for low-mass • For more massive galaxies • Hot gas may not be able to escape from the dark matter halo • IGM accretion needs to be considered • Hot gas properties thus depend on the environment and galaxy evolution

9. Outflow and galaxy formation: 1-D simulations z=1.4 • Evolution of both dark and baryon matters (with the final mass 1012 M☉) • Initial bulge formation (5x1010 M☉)  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 • The bulge wind can be shocked at a large radius. z=0.5 z=0 Tang et al 2009b

10. Outflow dynamics: dependence on the interplay between the feedback and the galactic environment • For a weak feedback, 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, as indicated by the observations

11. Subsonic Outflow: 3-D Simulations • 3-D simulation starting from a 1-D outflow initial condition • Luminosity boosted by a factor of ~5 • The predicted gas temperature and Fe abundance are closer to the observed. SN ejecta evolution Tang & Wang in prep

12. 3-D Subsonic Outflow Simulations: Results 1-D outflow model 3-D simulation 1-D wind model Positive temperature gradient,mimicking a “cooling flow”! Positive Fe abundance gradient, as observed in central regions of ellipticals

13. Conclusions • Hot gas in (low- and intermediate mass) ellipticals is in outflows driven by Ia SNe and stellar mass loss • 1-D galactic wind model cannot explain observed diffuse X-ray emission • 3-D hot gas structures can significantly affect observational properties • Outflow dynamic state depends on galaxy history and environment • Stellar feedback can play a key role in galaxy evolution: • Initial burst leads to the heating and expansion of gas beyond the virial radius • Ongoing feedback can keep the circum-galactic medium from cooling and maintain a hot halo

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

15. 3-D hydrodynamic simulations of hot gas in and around Galactic bulges • Mass, energy, and metal distributions • Comparison with observations • Effect on galaxy evolution Tang & Wang 2005, 2009 Tang et al. 2009

16. Hot gas in the M31 bulge • L(0.5-2 keV) ~ 31038 erg/s ~1% of the SN mechanical energy input! • T ~ 0.3 keV ~10 times lower than expected from Type Ia heating and mass-loss from evolved stars! • Mental abundance ~ solar inconsistent with the SN enrichment! IRAC 8 micro, K-band, 0.5-2 keV Li & Wang (2007); Li, Wang, Wakker (2009); Bogdan & Gilfanov 2008