feedback observations and simulations of elliptical galaxies –daniel wang, shikui tang, yu lu,...
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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)
NGC 4697: X-ray intensity contours 3-D stellar feedback simulation
Key questions to addressWhy do elliptical galaxies typically
evolve passively? Understanding the cause of the bi-
modality of galaxiesWhat 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
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)
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
dispersionToo steep radial X-ray intensity profileToo high Temperature, fixed by the specific energy
inputToo 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 1010 Msun spheroidAdaptive 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 kpc3 BoxDensity snapshot
Tang et al 2009Tang & 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 conditionOnly reasonable for low-mass
For more massive galaxiesHot gas may not be able to escape from the
dark matter halo IGM accretion needs to be consideredHot 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 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.
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 evolutionTang & 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
ConclusionsHot gas in (low- and intermediate mass) ellipticals is in
outflows driven by Ia SNe and stellar mass loss1-D galactic wind model cannot explain observed diffuse
X-ray emission3-D hot gas structures can significantly affect
observational propertiesOutflow dynamic state depends on galaxy history and
environmentStellar 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
Cosmological 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 evolutionTang & Wang 2005, 2009
Tang et al. 2009
Hot gas in the M31 bulgeL(0.5-2 keV) ~ 31038
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 ~ solarinconsistent with the SN
enrichment!
Li & Wang (2007); Li, Wang, Wakker (2009); Bogdan & Gilfanov 2008
IRAC 8 micro, K-band, 0.5-2 keV