PATRICIA B. TISSERA Institute for Astronomy and Space Physics Argentina i
Observational motivations Model Results
GALAXY FORMATION In the last years, studies of chemical elements obtained in the Local Universe and at high redshifts have improved dramatically. Chemical patterns are the result of different mechanisms which contribute to galaxy formation gas cooling and condensation growth of the structure: Collapse, infall and mergers star formation and stellar evolution environmental effects:starvation strangulation, etc supernova feedback: chemical + energy release
THE MILKY WAY DM HALO BULGE STELLAR HALO THIN DISC THICK DISC
Milky Way BULGE hz ~ 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 THIN DISC 1991;Chiba & Beers (2000 Rotationally supported: σ/v <<1. Scale-length ~ 2-2.5 kpc (Siegel et al. 2001), hz ~ 280 pc (σr, σphi, σz ) ~ (141, 106, 94) km/s Stellar age distribution ~ [2,14]Gyr and [Fe/H] peaks at ~ -0.2 (Nordstrom et al. 2004) THICK DISC scale-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. Patricia B. Tissera
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 FEEDBACK Some references on chemical modeling in cosmological simulations: Raiteri et al. (1996; also Berczik 1999) SNII & SNIa; Fe & H Mosconi, 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+SNE Okamoto 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; diffusion Wiersma et al. (2009): detailedse; smoothed metals+ Ekin
Supernova Feedback CHEMICAL ENRICHMENT SN: Main source of heavy elements Change the cooling time HYDRODYNAMICAL HEATING 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
CHEMICAL FEEDBACK Mosconi, Tissera, Lambas & Cora 2001 Numerical space Physical space Star particles Stellar populations Type II Sne Type Ia Sne Intermediate mass stars Need IMF: SNe long-lived stars M* > 8 Mo; typical life-times: ~ 106 yr Produce most O, Si, Ca, etc Typical life-times: ~ Gyr Main source of iron (Fe) YIELDS
Chemical evolution: the fossil records from Zocalli 2008 Relative abundances of alfa elements over Fe: Relative abundances of SNII with respecto to SNIa Formation timescale of the systems
CHEMICAL FEEDBACK When SN explosions take place, they distribute metals according to the SPH technique. For a given chemical element x at a particle i, Mxi = j mj/ρj Mxi W(rij,hij) Each neigbhour will receive Mxj =mj/ρj Mxi W(rij,hij) Exploding star particle Gaseous neighbours Mosconi, Tissera, Lambas & Cora 2001 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
Aquarius galaxies Scannapieco et al. 2008
T= (U2 +W2) Bulge V (km/s) Disc Inner H Outer H
Re-defining the disc components r (kpc/h) r (kpc/h) Disc cont. 16% Bar/T(p) = 0.23 [Fe/H] [Fe/H] r (kpc/h) Disc cont. 12 % Bar/T(p) = 0.34 [Fe/H] Disc cont. 7.5% Bar/T(p) = 0 r (kpc/h) r (kpc/h) r (kpc/h)
Star formation histories of each component Aq-A-5 Aq-C-5 Aq-D-5 Disc Bulge Inner Halo Outer Halo Age Gyr Aq-E-5 f Age Gyr Aq-G-5 Aq-F-5
Aq-A-5 Aq-C-5 Aq-D-5 f Aq-G-5 Aq-E-5 Aq-F-5 f Disc Bulge Inner Halo Outer Halo
The hierarchical building up of the structure
Stellar mass fraction in Inner Halo In satellites log z +1 log z + 1 Stellar mass fraction in Disc In situ Stellar mass fraction in Outer Halo Stellar mass fraction in Bulge Fraction of stellar mass formed in the progenitor and in substructure log z + 1 log z + 1
Median Fe enrichment for each component Disc Bulge Inner Halo Outer Halo
Median alfa-enhacement for each component Disc Bulge Inner Halo Outer Halo
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
Median [O/Fe] (O/H)c S(O/H) Mean age of Bulges Median age Median age Median age 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.
DISC COMPONENT Median properties of stars formed in situ and stars formed in satellites Aq-C [Fe/H] -0.93 [Fe/H]sat -1.23 [O/Fe] -0.17 Aq-D -0.91-1.02-0.078 Aq-G -1.01-1.07-0.11 [O/Fe]sat 0.27 Age 8.19 Age_sat 12.23 σ/vtan 0.55 σ/vtan 0.70 0.16 8.21 10.93 0.65 0.73 0.02 8.65 10.34 (Gyr) 0.57 0.71 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
Stellar mass fraction of old and metal-rich stars The fraction of old metal-rich stars show NO correlation with the history of formation.
The satellite systems 100 kpc/h
The satellite systems: star formation histories Aq-B-5 Aq-C-5 Stellar mass fraction Aq-A-5 Stellar mass fraction Aq-D-5 Age (Gyr) Aq-F-5 Aq-G-5
The satellite systems: chemical properties Chemical properties of the satellites which contribute to the formation of the main galaxies are different from those of the surviving satellites. Stripped stars Surviving satellites
Some conclusions... Bulges formed mainly in situ. Some might receive contribution from stars formed in subtructures. 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 lower level of enrichment. The median abundances correlate with the fraction of stars formed in 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.
Dynamics and chemistry: new interesting results coming soon..