Chemical Evolution of Galaxies: a problem of...
Transcript of Chemical Evolution of Galaxies: a problem of...
![Page 1: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/1.jpg)
Chemical Evolution of Galaxies: a problem of
Astroarchaelogy
Francesca Matteucci,
Trieste University
Lubljana, February 24, 2014
![Page 2: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/2.jpg)
Chemical Evolution of Galaxies
Beatrice Tinsley (27 January 1941- 23 March
1981) She started the field of
galactic chemical evolution
![Page 3: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/3.jpg)
Collaborators:
![Page 4: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/4.jpg)
Outline of the talk Definition of galactic chemical evolution Basic ingredients of chemical evolution The death of stars: planetary nebulae and
supernovae The effects of element production by stars
in galaxies Summary
![Page 5: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/5.jpg)
Chemical Evolution
Chemical abundances tell us about the nucleosynthesis as well as the formation and evolution of galaxies
Light elements (H, D, He, Li) were synthesized during the Big Bang
All the elements with A>12 were formed inside stars
Stars produce new elements and then restore them into the ISM. This process is chemical evolution
![Page 6: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/6.jpg)
Basic Ingredients of Chemical Evolution
Initial conditions (open, closed-box; initial chemical composition)
The stellar birthrate function: SFRxIMF The stellar yields (i.e. the mass restored
into the ISM by a star of a given mass in the form of a given chemical element) by stellar winds and supernovae
Gas flows: infall, outflow, inflow
![Page 7: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/7.jpg)
The Star Formation History
The star formation history depends on the SFR (star formation rate) and IMF (initial mass function)
The IMF describes the distribution of stellar masses at birth, the SFR tells how much gas goes into stars per unit time
The IMF (power law) has been derived in the solar vicinity (Salpeter, 1955; Scalo1986; Kroupa & al. 1993 ; Kroupa 2000+ others..)
![Page 8: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/8.jpg)
The parametrization of the SFR
The most common parametrization is the Schmidt (1959) law, where the SFR is proportional to some power (k=2) of the gas density
Kennicutt (1998) suggested k=1.4 from studying star forming galaxies. The quantity nu is the efficiency of star formation, expressed in t-1
![Page 9: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/9.jpg)
Kennicutt’s law
![Page 10: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/10.jpg)
![Page 11: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/11.jpg)
Stellar Yields Low and intermediate mass stars (0.8-8
Msun): produce He, N, C and heavy s-process elements (e.g. Ba). They die as C-O WDs, when single, and can die as Type Ia SNe when binaries
Massive stars (M>10 Msun, core-collapse SNe): they produce alpha-elements (O, Mg..), some Fe, light s-process elements and perhaps r-process elements? Merging of neutron stars a possible source
Type Ia SNe produce mainly Fe (0.6-0.7 Msun per SN) and Fe-peak elements(?)
![Page 12: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/12.jpg)
Metal dependent stellar yields (O, Fe) from core-collapse SNe (Nomoto & al.06)
![Page 13: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/13.jpg)
Supernova Progenitors
Core-collapse SNe originate from massive stars (M> 8Msun), they can be of Type II,Ib and Ic.They leave neutron stars or black holes as remnants. Type Ib/c SNe, M>30-40Msun , if single and 12-40Msun if binaries, are connected to GRBs. PCSNe M>100Msun (no remnant)
Type I a SNe are thought to originate from C-O white dwarfs (WD) in binary systems. Exploding by C-deflagration when reaching the Chandrasekhar mass. They do not leave any remnant
![Page 14: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/14.jpg)
Different supernovae
SN Ia (artistic view) SN II (Cassiopea A)
![Page 15: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/15.jpg)
Type Ia Supernovae Single-degenerate scenario (e.g. Whelan & Iben
1974; Hachisu et al. 1996; Han &Podsiadlowski 2004): a binary system with a C-O white dwarf plus a MS star. Minimum time for explosion 35 Myr!
Double-Degenerate scenario (Iben & Tutukov, 1984): two C-O WDs merge after loosing angular momentum due to gravitational wave radiation. Minimum time 36 Myr! Merging of He WD and C-O WD also possible
Empirical delay time distributions (DTDs) (Mannucci & al. 2006:Strolger & al. 2004; Totani & al. 2008; Pritchett & al. 2008)
![Page 16: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/16.jpg)
Gas flows
Gas can be accreted or lost from a galaxy The most common parametrization of the
accretion rate is an exponential law
![Page 17: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/17.jpg)
Gas Flows
Outflows and galactic winds are seen in galaxies
The most common parametrization is
Wind=CxSFR
The wind rate is proportional to the star formation rate (Martin, 2000,2004)
![Page 18: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/18.jpg)
Basic Equations
All these ingredients should be included in equations describing the evolution of the abundances of single chemical elements in the gas
These equations should be solved numerically if one wants to take into account in details stellar lifetimes
![Page 19: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/19.jpg)
Basic Equations
![Page 20: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/20.jpg)
The Milky Way
![Page 21: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/21.jpg)
The Formation of the MW from Astroarchaelogy
The two-infall model of Chiappini, FM & Gratton (1997) predicts two main episodes of gas accretion
During the first one the halo, bulge and all or part of thick disk formed, the second gave rise to the thin disk
This model can fit most of the observational data
![Page 22: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/22.jpg)
Main Assumptions for the Two-Infall Model
SFR- Kennicutt’s law with a dependence on the surface gas density (exponent k=1.5) plus a dependence on the total surface mass density (feedback). Threshold in the SF in the thin disk
Type Ia SN progenitors from the SD model (Greggio & Renzini 1983; FM & Recchi 2001). This scenario and the DD one are the best to reproduce chemical properties (FM & al. 2006; 2009). Yields from Woosley& Weaver 95 and van den Hoek & Groenewegen 97
IMF Scalo (1986) normalized over a mass range of 0.1-100 Msun
![Page 23: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/23.jpg)
Predicted SN rates in the MW in the two-infall model
Type II SN rate (blue) follows the SFR
Type Ia SN rate (red) increases smoothly
(small peak at 1 Gyr) SD as Type Ia
progenitors Oscillations are due
to the threshold in SF
![Page 24: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/24.jpg)
The G-dwarf Metallicity Distribution in Solar Vicinity
G-dwarf metallicity distribution compared with predictions of the two-infall model (Kotoneva et al. 2003)
The assumed timescale (8 Gyr) for disk formation is a very important parameter
![Page 25: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/25.jpg)
Abundance ratios in the MW, Solar Vicinity (Francois, FM &al. 2004)
According to the time-delay model
the ratios [X/Fe] vs. [Fe/H] can be explained by the different timescales on which different elements are produced
The alpha-elements (O,Mg,Si, S, Ca) are produced in core-collapse SNe on short timescales (from 1 Myr to 35Myr), whereas Fe is mainly produced on longer timescales (from 35 Myr to a Hubble time), but a fraction of it is also produced in core-collapse SNe
This interpretation explain the behaviour shown in the figure and it applies to any chemical element
![Page 26: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/26.jpg)
Effect of different yields
Predicted and observed [X/Fe] for two different sets of yields
Dashed lines:yields from Woosley & Weaver (1995) for massive stars and from van den Hoeck & Groenewegen (1997) for low and intermediate mass stars
Continuous lines: yields from Karakas (2010) for low and intermediate mass stars and from Geneva group for He, C, N,O with rotation and from Kobayashi & al. ( 2006) for heavy elements
Models from Romano & al. 2010
![Page 27: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/27.jpg)
Romano & al. 2010. Best yields: dashed line. Solar ab. Asplund & al. 2009
![Page 28: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/28.jpg)
The time-delay model and different star formation rates
Predicted [alpha/Fe] ratios for different SFR histories (a more modern version of FM & Brocato 1990)
A strong starburst (dashed line), a SFR like in the solar vicinity (dotted) and a slow SFR (continuous) like in Magellanic Irregulars or Dwarf Spheroidals
![Page 29: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/29.jpg)
The Galactic Bulge
Model (black, Cescutti & FM 2011): fast Bulge formation (0.3 Gyr) and IMF flatter than in S.N.
Predicts large Mg to Fe for a large Fe interval
Turning point at larger than solar Fe (effect of the time-delay model)
Data from giants and dwarfs. Bensby & al. 2010; Alves-Brito & al. 2010
![Page 30: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/30.jpg)
Two Bulge populations?
Two populations: i) classical bulge, fast formation (0.3 Gyr), ii) younger stars related to the bar, longer formation (3-4 Gyr)
Model by Grieco, FM & al. 12 compared to Hill & al’s (2011) data
Salpeter IMF MDF convolved with
an error of 0.25 dex
![Page 31: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/31.jpg)
Abundance Gradients in the Galactic Disk Predicted and observed
abundance gradients from Chiappini, FM & Romano (2001). Disk forms inside-out:
tau(R)=1.033R(kpc) -1.27 Gyr. A SF threshold is considered (7Msunpc-2)
Data from HII regions, PNe and B stars, red dot is the Sun
The gradients slightly steepen with time (from blue to red)
![Page 32: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/32.jpg)
Abundance Gradients in the Galactic Disk Different models with
and without radial inflows (Spitoni & FM 2011)
Black line, no flows no threshold inside-out, red line radial flows of speed 1 Km/sec
Blue line a variable speed for radial flows
![Page 33: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/33.jpg)
Gradient inversion at z=3 with and without radial flows
![Page 34: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/34.jpg)
Summary from Astroarchaelogy of the Milky Way The inner stellar Halo must have formed on a timescale
of 0.8-1.5 Gyr whereas the outer Halo must have formed on a longer timescale (inside-out Halo formation)
The local disk must have assembled by gas accretion on a time scale from 6-8 Gyr and the timescale increases with galactocentric radius
The Bulge stars of the classical component must have formed on a time no longer than 0.3-0.5 Gyr with flatter IMF. The stars related to the bar should have formed on longer timescales
A gradient inversion at z=3 is predicted by the two-infall model with and without radial flows. Observed by Cresci & al. (2010). It is due to the inside-out formation
![Page 35: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/35.jpg)
Dwarf Spheroidals of the LG vs. Milky Way (Shetrone+02)
![Page 36: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/36.jpg)
Dwarf Spheroidals vs. Milky Way
The [alpha/Fe] ratios in dSphs evolve differently as a function of [Fe/H]
There is some overlapping of the
[alpha/Fe] ratios only at low metallicity Can the dSphs have been the building
blocks of the Galactic halo? Chemical abundances should reveal it
![Page 37: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/37.jpg)
Chemical Evolution of Dwarf Spheroidals Chemical models for dSphs (Lanfranchi &
FM, 2004) suggest that they evolved slowly with a low SF efficiency and suffered strong winds
SF lasted for long periods either continuous or in bursts
This explains the sharper decrease of the [alpha/Fe] ratios relative to the MW
![Page 38: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/38.jpg)
Carina: data vs. models
Best Model for Carina by Lanfranchi+( 2006) compared with data from Koch + (2008)SF history taken from Color-Magnitude diagramFour bursts of SF with SF efficiency 0.15Gyr-1
![Page 39: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/39.jpg)
Sculptor: data vs. models
Data for Sculptor (Kirby et al. 2009, Shetrone et al. 2003, Geisler et al. 2005)
One extended episode of SF, strong wind: models from Lanfranchi & FM (2009) in red (SF eff. 0.2 Gyr-1 )
![Page 40: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/40.jpg)
The Ultra Faint Dwarfs-Koch & al. (2012) Better candidates for
the Galactic halo are theultra-faint-dwarfs (UFD) ?
Stars refer to the UFD Hercules, black points are the MW and blue points the dSphs
Models with very low SF efficiency (from 10-4 to 0.1Gyr-1 )
![Page 41: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/41.jpg)
The Galactic Halo and First Stars Caffau & al. (2011) have discovered a halo star
with Z <4.5 10-5 Zsun! Keller+2014 a star with [Fe/H]<-7.0!
Is the existence of massive PopIII stars compatible with that metallicity?
PopIII stars should have formed at z=20, been massive (Bromm 2002) from 10Msun and possibly >200Msun (PCSNe) for Z< Zcrit=10-4 Zsun
The Caffau star is below the Zcrit for passing from PopIII to low mass PopII
Are there PopIII stars with low mass? (see Clark+ 2011)
![Page 42: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/42.jpg)
Galactic Halo MDF: the effect of PopIII stars (Brusadin,FM&al.13) Predicted and observed
MDF in the Galactic halo (Brusadin, FM&al. 2013)
PopIII stars are present in both models with different IMFs
Case I: stars from 10 to 260 Msun, one slope x=1.7 for Z<Zcrit
Case II: IMF as in Salvadori & al. (2007) one slope x=1.35 but variable low cut-off
![Page 43: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/43.jpg)
Summary Astroarchaeology by means of chemical abundances
can allow us to impose constraints both on stellar nucleosynthesis and star formation hystory
We can reasonably well reproduce the chemical abundances in the solar vicinity. For some elements the yields are still very uncertain
The roles of SNe of different Types (time-delay model) help in interpreting abundance patterns
Prompt Type Ia SNe seem to be necessary in all galaxies to fit chemical abundances
A crucial parameter in galaxy evolution is the efficiency of star formation
The MDF of the halo is best fitted without massive PopIII stars
![Page 44: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/44.jpg)
Summary
Dwarf spheroidals and ultra faint dwarfs in the Local Group should have suffered a star formation rate with much lower efficiency than in the Milky Way, as well as strong galactic winds
It is difficult to assess whether these galaxies have been the building blocks of the MW halo which can be well reproduced by in situ SF
The bulge of the MW seems more complex than previously thought. Two different populations are identified, one of which is old and formed fast
The MW disk could have formed inside-out and this implies an inversion of the O gradient at high redshift, due to the strong inner infall at early times
Abundance gradients can put constraints on the mechanism of disk formation
![Page 45: Chemical Evolution of Galaxies: a problem of Astroarchaelogydunja/AD/presentations/AD_2014-02-24_FM.pdf · Chemical Evolution Chemical abundances tell us about the nucleosynthesis](https://reader036.fdocuments.us/reader036/viewer/2022081612/5f52b8ff79673e0121583469/html5/thumbnails/45.jpg)