PATRICIA B. TISSERA

Institute for Astronomy and Space PhysicsArgentina

i

Observational motivationsModelResults

gas cooling and condensation

star formation and stellar evolution

supernova feedback:chemical + energy release

environmental effects:starvationstrangulation, etc

GALAXY FORMATION In the last years, studies of chemical elements obtained in the Local Universeand at high redshifts have improved dramatically.

Chemical patterns are the result of different mechanisms which contribute togalaxy formation

growth of the structure:Collapse, infall and mergers

THE MILKY WAY

BULGE

DM HALO

THIN DISCTHICK DISC

STELLAR HALO

Patricia B. Tissera

Milky Way

BULGEhz ~ 2 kpc; averged age ~ 10 Gyr for stars with hz >

400 pc

metallicity peak: [Fe/H] ~ -0.3 dex ( Zoccali et al.

2003).

there are young stars and on-going star formation

( Van Loon et al. 2003)

Stellar Halor:J/M ~ 0 (Freeman 1987); sopported

by dispersion

<[Fe/H] > ~ -1.5 dex (Ryan & Nories

1991;Chiba & Beers (2000

(σr, σphi, σz ) ~ (141, 106, 94) km/s

THIN DISCRotationally supported: σ/V <<1.

Scale-length ~ 2-2.5 kpc (Siegel et al. 2001), hz ~ 280 pc

Stellar age distribution ~ [2,14]Gyr and [Fe/H] peaks at ~ -0.2

(Nordstrom et al. 2004)

THICK DISCscale-lenght ~ 3 kpc , hz ~ 1 kpc (assuming a double

exponential) .

t_median ~ 12.5 +- 1.4 Gyr (Liu &Chaboyer 2000)

-2.2 < [Fe/H] <0.5 with <[Fe/H]> ~ -0.6 (Chiba & Beers

2000)

higher [O/Fe] than the stars in the thin disc.

Luminosity-metallicity and mass-metallicity relations:

There are well-known LMR and MMR in the local Universe.Observations suggest evolution in the zero point and slope of both relations.

SDSS: Tremonti et al .2004

Erb et al 2006: z~2.5

CHEMICAL FEEDBACKSome references on chemical modeling in cosmological simulations:

Raiteri et al. (1996; also Berczik 1999) SNII & SNIa; Fe & HMosconi, Tissera, Lambas & Cora. (2001): SNII & SNIa, Eth. Lia, Portinari & Carraro (2002):detailed SE; diffusion Kawata & Gibson (2003): SNII, SNIa,IS; Eth +Ekin Springel & Hernquist (2003): Z + Twophases +Ekin Kobayashi (2004; et al. 2006):detailedSE; Eth +Ekin Scannapieco et al. (2005, 2006): SNII & SNIa + Multiphase+SNEOkamoto et al. 2006: SNII+SNIa+Twophases+Ekin (+top heavy Imf) Oppenhaimer & Dave (2006): SNII &SNIa + Twophases + Ekin Stinson et al. (2006): SNII&SNIa + cooling off Martinez-Serrano et al. (2008): detailedSE; diffusionWiersma et al. (2009): detailedSE; smoothed metals+ Ekin

Supernova Feedback

CHEMICAL ENRICHMENT HYDRODYNAMICAL HEATING

SN: Main source of heavy elements

Change the cooling time

evaporates cold-dense gas galactic winds which can results in outflows or galactic fountains

•Regulates the star formation activity and enriches the ISM and IGM•Affects the gas dynamics: disc formation

•This might leave chemical fossils which can be used •to track the formation history of a galaxy

Intermediate mass stars

CHEMICAL FEEDBACK

Numerical space Physical space NeedStar particles Stellar populations

↔

IMF:SNelong-lived stars

M* > 8 Mo; typical life-times: ~ 106 yrType II Sne

Typical life-times: ~ GyrMain source of iron (Fe)Type Ia Sne

Produce most O, Si, Ca, etc

YIELDS

Mosconi, Tissera, Lambas & Cora 2001

Chemical evolution: the fossil records

from Zocalli 2008

Relative abundances of alfa elements over Fe:

Relative abundances of SNII with respecto to SNIaFormation timescale of the systems

Mosconi, Tissera, Lambas & Cora 2001

When SN explosions take place, they distribute metals according to the SPH technique. For a given chemical element x at a particle i,

Exploding star particle

Gaseous neighbours

CHEMICAL FEEDBACK

Mxi = ∑j mj/ρj Mxi W(rij,hij)

Mxj =mj/ρj Mxi W(rij,hij)

Each neigbhour will receive

i j

★ A GADGET-3 (Springel 2005) with:

Stochastic star formation (Springel & Hernquist 2002)

Chemical enrichment from Type II and Ia Supernovae and metal dependent cooling

Multiphase gas model: allows overlap of dense and diffuse gas

Supernova feedback: distributes energy separately for cold and hot pre-defined phases (thermal feedback + reservoir for cold phases) within the context of the Multiphase gas model.

All this implemented without scale-dependent parameters well suited to run cosmological simulations where systems of different mass form simultaneously.

Scannapieco, Tissera, White & Springel 2005,2006,2008

Scannapieco et al. 2006

Aquarius haloes

8 galazy-sized haloes of 1012 Mo (Springel et al. 2008) selected

from a Λ-CDM cosmological volume of 100 Mpc/h box , with mild

isolation criterion.

ICs have been modified to include baryons.

approx half a millons particle per specie

Run with GADGET-3 including chemical evolution.

Can these simulations reproduce general trends?

Can we link the chemical properties to their histories of assembly?

Tissera, White & Scannapieco in prepration

Scannapieco et al. 2008

Aquarius galaxies

T=

(U

2 +

W2 )

Bulge Disc Inner H Outer H

V (km/s)

Disc cont. 16%Bar/T(p) = 0.23

Disc cont. 7.5%Bar/T(p) = 0

Disc cont. 12 %Bar/T(p) = 0.34

Re-defining the disc components

r (kpc/h) r (kpc/h) r (kpc/h)

r (kpc/h) r (kpc/h) r (kpc/h)

[Fe/

H]

[Fe/

H]

[Fe/

H]

Aq-E-5

Star formation histories of each component

Age Gyr

Aq-A-5

Disc

Bulge

Inner Halo

Outer Halo

Aq-C-5 Aq-D-5

Age Gyr

f

Aq-F-5Aq-G-5

f

f

Aq-A-5 Aq-C-5 Aq-D-5

Aq-E-5 Aq-G-5 Aq-F-5

Disc Bulge Inner Halo Outer Halo

The hierarchical building up of the structure

log z +1 log z + 1

log z + 1 log z + 1

Fraction of stellar mass formed in the progenitor and in substructure

Ste

llar

mas

s fr

actio

n in

Bul

ge

Ste

llar

mas

s fr

actio

n in

Dis

c

Ste

llar

mas

s fr

actio

n in

Inne

r H

alo

Ste

llar

mas

s fr

actio

n in

Out

er H

alo

In situ

In satellites

Disc

Bulge

Inner Halo

Outer Halo

Median Fe enrichment for each component

Disc

Bulge

Inner Halo

Outer Halo

Median alfa-enhacement for each component

There is a

correlation between

the fraction of stellar

mass formed in situ

and the fraction of

stellar mass formed

in massive satellites

(M > 0.5 1010 Mo/h).

The level of enrichment of stars in the halo tend to correlates with the fraction of mass formed in massive satellites:

the larger this fraction, the higher the median abundance of the halo

Metallicity gradients

Observations from Dutil et al. 1997

Metallicity gradientes and history of formation

Mean age of Bulges

The faster the bulge formed its stars, the steeper and higher its Oxygen abundances and the higher its [alfa-Fe] content.

Nevertheless, there is important dispersion in the correlations.

Median age Median age Median age

S(O

/H)

(O/H

)c

Med

ian

[O/F

e]

[Fe/H] [Fe/H]sat [O/Fe] [O/Fe]sat Age Age_sat σ/vtan σ/vtanAq-C -0.93 -1.23 -0.17 0.27 8.19 12.23 0.55 0.70

Aq-D -0.91 -1.02 -0.078 0.16 8.21 10.93 0.65 0.73

Aq-G -1.01 -1.07 -0.11 0.02 8.65 10.34 0.57 0.71 (Gyr)

DISC COMPONENT

Median properties of stars formed in situ and stars formed in satellites

Stars on the disc coming from satellites tend to have lower metallicity and higher[alfa-Fe] than those formed in situ.

Kinematically they are, on average, more consistent with belonging to a thick disc

Stellar mass fraction with very low metallicity

The fraction of

old metal-rich

stars show NO

correlation with

the history of

formation.

Stellar mass fraction of old and metal-rich stars

The satellite systems

100 kpc/h

The satellite systems: star formation histories

Aq-B-5Aq-A-5

Aq-F-5Aq-D-5 Aq-G-5

Age (Gyr)

Ste

llar

mas

s fr

actio

nS

tella

r m

ass

frac

tion

Aq-C-5

Chemical properties of the satellites which contribute to the formation of the main galaxies are different from those of the surviving satellites.

The satellite systems: chemical properties

Surviving satellites

Stripped stars

Bulges formed mainly in situ. Some might receive contribution from stars formed insubtructures. The level of enrichmnet and [alfa/Fe] anticorrelates with this fraction: Systems formed mainly by infall have older stellar populations, larger [alfa-Fe] , higher O/H abundances and speeper gradients.

Haloes formed mainly by contribution from substructure. Stars tend to be old with lowerlevel of enrichment. The median abundances correlate with the fraction of stars formedin massive satellites. It matter how they were assembly. The have very flat gradients.

The disc component formed mainly in situ and in several starbursts resulting in a population with lower [O/Fe] content. There could be contribution from satellites (~15%) and these stars are older, alfa enhanced and high velocity dispersion than those stars formed on the disc. Simulated gradients are consistent with observations.

Satellites that contribute to the formation of the main galaxies have very different chemical properties than those that survive in the haloes.

Some conclusions ...

Dynamics and chemistry: new interesting results coming soon..