Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Supernova outflows in galaxy formation
Institute for Astronomyand Space Physics
Buenos Aires - Argentina
Cecilia Scannapieco
Max-Planck Institute for Astrophysics
Garching – Germany
Simon White & Volker SpringelPatricia Tissera
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Outline Introduction: Supernovae and galaxy formation
Implementation of Supernova feedback in numerical
simulations
Results for Isolated galaxy formation models:
Dependence on input parameters
Outflows
Self-regulation of the star formation process
SN feedback and dwarf galaxies
Conclusions and Future Work
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Introduction: Why do we care? Supernovae (SNe) explosions play a fundamental role in the evolution of galaxies
Ejection of metals: effects on the cooling process Ejection of energy: effects on the gas collapse
Effects on the star formation activity
Observations: Galactic winds and fountains, chemical enrichment of the intracluster medium, ......
Numerical simulations: hard to model, high computational cost, unknown physics, ….
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
The Model - I Tree-PM code GADGET-2 (Springel 2005). Entropy formulation Star formation: stochastic approach (Springel & Hernquist 2003)
(entirely gaseous or stellar particles) Multiphase gas (relative decoupling of neighbours) Chemical enrichment (Scannapieco et al. 2005a, astro-ph/0505440)
SNII SNIa
Yields Woosley & Weaver (1995) Nomoto et al. (1998)
Release Instantaneous [ 0.1 , 1 ] Gyr
Rate given by IMF 1/3 RateSNII (van derBergh 1991)
Most chemical elements Fe
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
The Model - II Energy feedback (Scannapieco et al. 2005b):
“Cold-dense” and “Hot” gaseous phases Energy deposited separately:
Distribution of metals and energy: SPH technique
Metal-dependent cooling (Sutherland & Dopita 1993)
No resolution-dependent or ad-hoc parameters which might depend on virial temperature
Hot: fhot, instantaneous with SN explosions Cold: fcold, “promotion scheme”
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Simulations of Isolated disk galaxies Spherical grid with superposed DM and Gas particles: perturbed radially to give rise to a ρ ~1/r profile
Virial Mass : 1012 h-1 Mo ( h = 0.7 )
Baryonic Mass : 1011 h-1 Mo
Spin parameter : λ = 0.1
Number of particles : N = 10000 each
Star Formation Efficiency : c = 0.1
Initially primordial abundance: X=0.76 - Y=0.24
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Promotion & Outflows Heating of cold and dense gas in star forming sites Transportation of gas to the halo
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback: Effects on mass distribution Hot gas Cold gas Stars
No Feedback
Feedback
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback & hydrodynamical propertiesSN feedback produces a significant increase in the hot gas fraction and unbound fraction
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback: Effects on Star FormationHeating up of cold gas + transportation to halo:
decrease of the cold gas density
Self – regulation of the star formation activity
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback: Effects on metal distributionOutflows transport enriched material:
Chemical contamination of the haloes Gas takes a larger fraction of the metals from the stars
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback: Effects on metal distribution
Projected Gas Metallicity DistributionNo Feedback Feedback
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback & Dwarf GalaxiesSimulations of a 1010 Mo h
-1 total mass system SN feedback has crucial effects Most of the gas escapes from the system Significant reduction in the final stellar mass formed Strong feedback: No cold disc – Weak star formation
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
SN feedback & Dwarf Galaxies II
No Feedback
Feedback
Hot gas Cold gas Stars
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Conclusions I We have implemented a model for multiphase gas and Supernova
feedaback within GADGET-2, which is suitable to study galaxy formation in a cosmological framework, and does not introduce any scale-dependent parameter. SN feedback constitutes an effective mechanism to self-regulate the
star formation activity through the heating of the cold gas in the discs and its transportation to outer regions of galaxies.
As the gas in the discs is highly enriched, the outflows lead to a contamination of the haloes. This could explain the presence of metals in the intergalactic medium.
Cecilia Scannapieco Marseille Cosmology Meeting June 2005
Conclusions II
SN feedback would have a major impact in dwarf galaxies.
Depending on the strength of the feedback, cold central cores could not be able to form.
Next step: adjust input parameters (basically strength of the feedback) with a high resolution simulation of a Milky Way type galaxy and comparing to observational results.