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) NGC 4697: X-ray intensity contours 3-D stellar feedback simulation

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 ☉ /10 10 L B ☉ /yr  Energy input from Ia SNe with a rate ~ 0.2 /10 10 L B ☉ /100yr  Specific temperature: T ~ 1-2 Kev  Fe abundance ~Z * +5(M SN /0.7M sun )  traced by X-ray

Observations of stellar feedback Large scattering of L X for galaxies with the same L B or L K Observed Lx is <10% of the energy inputs Mass of Diffuse gas ~ 10 6 – 10 7 M ☉, can be replenished within 10 8 yrs. David et al (2006) AGN SNe

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

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

Galactic wind: 3-D simulations 5 x M sun 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 10x10x10 kpc 3 Box Density snapshot Tang et al 2009 Tang & Wang 2009

3-D effects 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. Differential Emission Measure

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

Outflow and galaxy formation: 1-D simulations Evolution of both dark and baryon matters (with the final mass M ☉ ) Initial bulge formation (5x10 10 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. Tang et al 2009b z=1.4 z=0.5 z=0

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

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 Subsonic Outflow: 3-D Simulations

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

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

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. Hot gas Total baryon before the SB Total baryon at present Cosmologi cal baryon fraction

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

Hot gas in the M31 bulge L (0.5-2 keV) ~ 3  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! Li & Wang (2007); Li, Wang, Wakker (2009); Bogdan & Gilfanov 2008 IRAC 8 micro, K-band, keV