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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. Key questions to address.

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feedback observations and simulations of elliptical galaxies
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

key questions to address
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
slide3
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

slide4
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.
galactic wind
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
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

3 d effects
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.
slide8
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
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

outflow dynamics dependence on the interplay between the feedback and the galactic environment
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
subsonic outflow 3 d simulations
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

3 d subsonic outflow simulations results
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

conclusions
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
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.
3 d hydrodynamic simulations of hot gas in and around galactic bulges
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
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

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