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.