Chemical composition of the stars in the substructures of the Galaxy

(-1 <[Fe/H] > 0.3)

Mishenina T.V.

1 -Astronomical Observatory of Odessa National University ,

Shevchenko Park, 65014, Odessa, Ukraine ;

Workshop – SCOPES – Odessa 2011

Workshop Odessa-2011

Introduction• Any chemical element abundance, beginning from

hydrogen to neutron-capture elements, allows to testing and improving of cosmological theories, of theories of nucleosynthesis and stellar evolution, and the theory of formation and chemical evolution of galaxies.

•

• The behaviour of n-capture element’s abundance in the substructures of the Galaxy is of our particular interest.

• Depending on the density of a neutron flux, two main nuclear mechanisms, namely, the s-, r- processes, are responsible for the n-capture element’s abundance.

s- process• Three components of s-process: main, weak, strong (Kappeler et al.,

1989);

• Up–to-date calculations of the s-process element's yield in AGB stars are used code FRANEC (Chieffi et al.,1998), are taken into account

• the dependence of the yield on metallicity (Galino et al., 1998, Busso et al., 1999),

• the critical role of the third dredge up episode of mixing (Straniero et al., 2003,

• multicomponent contribution in production of an isotope (Serminato et al., 2009).

• Main component: two sources of neutrons in the low mass AGB stars:

• 13C (alpha, n) 16O, operated at the phase between pulsations under

• radiative conditions,

• 22Ne(alpha, n)25Mg, were occured during the thermal instability in convection condition (Serminato et al., 2009).

• In stars AGB of intermediate-mass (M > 4.5 M_sun) the main role • plays the reaction 22Ne(alpha, n)25Mg,

---weak component of the s - process – A up to 90, at high temperatures (Karakas&Lugaro, NIC2010)

---Strong component – 50% 208Pb, AGB

r-process• The origin of the r - process elements of (A > 56) remains

controversial. Three sources: • 1) the neutrino-induced winds from the supernova

(Woosley et al., 1994), • 2) the enriched neutron matter due to merging of neutron

stars (Freiburghaus et al., 1999, and others), • 3) winds from the merger of neutron stars or a neutron star

and black hole (Surman et al., 2008).• the two-component of r - process nucleosynthesis: • it is scaled solar r-process, and • some additional source of r-process. The alternative

sources have been proposed in some papers (Travaglio et al., 2004, Qian & Wasserburg 2008), but it has not clarified the situation yet.

Substructures of the galactic disk• Gilmore&Reid (1983) - density of stars: two different

exponentials with different height scale and density - “thin” disk, "thick“ disk: different kinematics, rotate, age, α – elements abundance

• O and Mg overabundance (Gratton et al., 1996; 2000; Fuhrmann, 1998; Chen et al., 2000 etc) for thick disk

• Neutron-capture elements behavior with metallicity was carried out in some papers:

• Eu (Prochaska et al., 2000), Ba, Eu (Mashonkina&Gehren, 2000, 2001); Nd (Mashonkina et al., 2004); Y, Zr, Ba, La, Ce, Nd, Eu (Brewer&Carney, 2005);Y, Ba, Eu (Bensby et al., 2005);Y, Ba, Ce,

Nd, Eu (Reddy et al., 2006); Y, Ba (Nissen&Shuster, 2008) etc.

• In general, the neutron-capture elements pattern shows that the contributions of s-, r-processes are different for the thin and thick discs element enrichment.

Aims:• Selection of the stars of the thin and thick disks, and the

Hercules stream;

• Determination of Y, Zr, Ba, La, Ce, Nd, Sm, and Eu abundances;

• Analysis of the alpha-elements, Ni and the neutron-capture elements pattern in the stars belonging to various substructures;

• Evaluation of the contributions of the s- and r-processes in the n-capture elements abundances;

• Consideration of possible sources of the n-capture elements production;

• Comparison with models of galactic enrichment.

Observations, Methods of spectral processing

• The spectra of 280 stars ( F-G-K V, G-K III) were obtained using the facilities of the 1.93 m telescope of the Haute-Provence Observatoire (France)

• equipped with the echelle spectrograph ELODIE (Baranne et al., 1996)

• Resolving power is 42 000, the region of the wavelengths was 4400 – 6800 ÅÅ, S/N ~ 100 – 300

• Reduction and the library of stellar spectra - Katz et al. 1998, Prugniel & Soubiran, 2001

• DECH20 (Galazutdinov , 1992)

Selection of the stars• Method : (Soubiran&Girard, 2005)

• thin disk thick disk

• Vlag (km/s) -15 -51

{U} (km/s) 39 63 {V} (km/s) 20 39 {W} (km/s) 20 39

The probability of each star, with a measured velocity (U,V,W), to belong to the thin disk (Pr1) and to the thick disk (Pr2)

The Hercules stream (Soubiran&Girard, 2005)

Parameters determination

• Teff were estimated by the line depth ratio R1/R2 method (Kovtyukh V.V.),

• dTeff = ± 5 – 10 K for dwarfs

• + H fitting (metal-poor)

Parameters determination

• Teff were estimated by the line depth ratio R1/R2 method (Kovtyukh V.V.),

• dTeff = ± 5 – 10 K for dwarfs

• + H fitting (metal-poor)

log g for dwarfs:two methods (ionisation balance of iron IE and using parallaxes P) <loggIE –loggP> = -0.06 ±0.16 (Teff > 5000 K, 80 stars)(loggP - Allende Prieto et al.,1999)

Parameters determination

• Teff were estimated by the line depth ratio R1/R2 method (Kovtyukh V.V.),

• dTeff = ± 5 – 10 K for dwarfs

• + H fitting (metal-poor)• Vt – independence of log A(Fe)

from EW for Fe I lines

• [Fe/H] – the iron abundance determined from Fe I lines

log g for dwarfs:two methods (ionisation balance of iron IE and using parallaxes P) <loggIE –loggP> = -0.06 ±0.16 (Teff > 5000 K, 80 stars)(loggP - Allende Prieto et al.,1999)

Comparison of our Teff with those estimated by Alonso et al.(1996), Blackwell Lynas-Gray (1998), di Benedetto (1998),

crosses – the stars with [Fe/H] < -0.5 (left panel); [Fe/H] vs. Teff (right panel), (Mishenina et al., 2004).

Abundance determination• Kurucz’s models (LTE)• WIDTH9, LTE (Kurucz R.) – Fe, Y, Zr, La, Ce, Nd,

Sm;

• log gf(solar) (Kovtyukh Andrievsky , 1999) with 9-12 lines of YII, 3-4 lines of ZrII, 5-6 lines of La II, 10-13 lines of CeII, 8-11 lines of NdII, 4-5 lines of Sm II.

• STARSP, LTE (new version) (Tsymbal V. , 1996) – Eu• Modified MULTI, NLTE (Carlsson M., Korotin S.) –

Mg, Ba• Differential approach: the spectra of Moon and

asteroids obtained with ELODIE as solar spectrum • The total uncertainty due to parameter and EW errors

for Fe I, Fe II is 0.10, 0.12, respectively.

The total uncertainty due to the parameter and EW ( fitting) errors

• for dwarfs: HD 139813 : 5408/4.5/1.2/0.0

Teff = ±100 K; log g = ±0.2 dex; Vt = ±0.2 km/s; [FeH]= ±0.25 and • an uncertainty of ±2 mA in the EW• an uncertainty of 0.02 dex in fitting of profiles

Elem Teff lgg Vt [Fe/H] Sp TotalY 0 -0,11 -0,02 0,07 0,02 0,13Zr 0,01 -0,12 0 0,07 0,02 0,14La 0 -0,12 0 0,07 0,02 0,14Ce -0,01 -0,12 -0,01 0,07 0,02 0,14Nd -0,02 -0,13 -0,01 0,07 0,02 0,15Sm -0,02 -0,13 -0,01 0,08 0,02 0,15

Eu abundance determination

STARSP LTE spectral synthesis code (Tsymbal, 1996), hyperfine structure (Steffen, 1985)Total errors ~ 0.15 dex

NLTE Ba abundance determination (Korotin S.A.)Ba atom model: 31 levels of Ba I, 101 levels of BaII, and the

ground level of BaIII + 91 bound-bound transitions.

alpha-elements: O, Mg, Si and Ca abundances are diminishing with the metallicity

increasing

Nickel as iron-peak elements

Ni distribution centred on [Ni/Fe] = 0, slightly rising at [Fe/H] > 0, and with a remarkably low dispersion

N-capture abundances in the stars of the disks: elements of s-process: Y and Zr

Such different trends: the lesser contribution of the s-process to the abundance for Zr relative to Y for the stars of the thick disk s-contribution in Y solar: 66 % (Sermitnato et al., 2009); 92% (Arlandini et al., 1999)s-contribution in Zr solar: 60% (Sermitnato et al., 2009); 83% (Arlandini et al., 1999)

heavy elements of s-process: Ba, La, Ce vs. [Fe/H]

• Ba has underabundance in the thick disk comparing to the thin disk

• [La/Fe]: the remarkable deficit at [Fe/H] > 0 • [Ce/Fe]: there is no trend with [Fe/H] • s-contribution in La solar: 66% (Serminato et

al., 2009)

heavy elements of s-process: Nd, Sm vs. [Fe/H]

[Nd/Fe] and [Sm/Fe] shows a slightly different trends with [Fe/H];

Nd, Sm abundances in the thick disk stars higher than those in the thin disk

Abundance of r-process element Eu vs. [Fe/H]

• Europium, the element formed predominantly in r-process (80 – 90 % in solar abundance)

•

• a marked trend with [Fe/H] and a slight Eu overabundance for the thick disk

Trends of Ba and Eu abundances on [alpha/Fe]

The correlation of [Eu/Mg] vs. [alpha/Fe] – SN II of 8 -10 M_sun (?)

The dependence of [Ba/Fe] vs. [alpha/Fe] – different sources

The yttrium, barium and magnesium behaviour [Y/Mg], [Ba/Mg] vs. [Mg/H] and [Y/Ba] vs. [Ba/H] , [Ba/Y] vs. [Y/H]

Mashonkina et al., 2004: [Nd/Ba]r=0.36, [Nd/Eu]r=-0.33

Y, Zr, Ba, La, Eu abundance with r-, s- process yields (Serminato et al., 2009)

• s – process: low mass AGB stars (1.5 – 3 M☺)

• r – process: residual method: r+s=1,

• SN II, M ~ 8 – 10 M☺

• Model – Code Ferrini et al., 1992

• Travaglio et al., 1999, 2001, 2004 + new grid of AGB yields (Chieffi et al., 1998)

Y & Zr: Serminato et al. 2009

• well represented by the theoretical total contribution of the s + r-processes.

as the circumflex curve for the observation data; some underproduction of the s-process in the Zr abundances or underestimated percentage contribution of the s-process to the solar zirconium abundance

Ba & La: Serminato et al. 2009

poorly specified by the estimated s+r processes curve for the thin disc stars with [Fe/H] > 0.1 dex and [Fe/H] < -0.2 dex

for the stars of the thin disc, both curves, representing the contributions of the s-process only and the total contribution, are circumflex

Eu: Serminato et al. 2009

• In the range of metallicity of around -1.0 - -1.5 dex, the values of the Eu abundance are lower in the thick disk than those in the thin disk that is contrary to

the observations.

[Ba/Eu], [La/Eu] vs. [Fe/H] :Serminato et al., 2009

Conclusions: Serminato et al., 2009 • Abundance trends with metallicity for Zr, La, Eu, and, especially, for Ba, can not be described by taking into account the s-process yields only of the AGB low-mass stars and using the residual method for the r- process;•The observed difference in the abundance and behavior of the elements of the thin and the thick disks is much larger than that predicted by the model.

Stars with large proper motions (Klochkova et al., 2011)6-m telescope, SAO RAN, near UV spectra, R = 60 000

NLTE Mg, Al, Sr, Ba (Korotin S.)

LTE Th, Eu (Mishenina T.)

HD 22879

HD 22879 HD 237354

HD 115 444 BD +80 245kinematic: thin disk accreted halo • Teff = 4800,

• log g = 1.6• [Fe/H] = -2.91• [Mg/Fe] = 0.77• [Ca/Fe] = 0.48• [Mn/Fe] =-0.50• [Ni/Fe] = -0.01• [Sr/Fe] = 0.07• [Y/Fe] = 0.04• [Ba/Fe] = 0.68• [Eu/Fe] = 1.26

• Teff =5543,• log g = 3.5• [Fe/H] = -1.71• [Mg/Fe] = -0.17• [Ca/Fe] = -0.24• [Mn/Fe] =-0.22• [Ni/Fe] = -0.05• [Sr/Fe] = -0.72• [Y/Fe] = -0.64• [Ba/Fe] = -1.46 !

Conclusions • Atmospheric parameters (Teff, logg , [Fe/H], Vt), and Y,

Zr, Ba, La, Nd, Sm, and Eu abundances in about 280 stars were determined upon a high resolution, high signal to noise ratio spectra obtained with the ELODIE echelle spectrograph at the OHP (France).

• The selection of stars to thin and thick disks, and Hercules stream was made on kinematic criterion.

Conclusions• The different trends of the n-capture elements with

metallicity in the thin and thick disks indicate that the contribution of the s- and r-processes in their content is different, and the sources of their production are also different; and their sources and yield should be considered separately for each element.

• To construct an adequate picture of the galactic enrichment, it is necessary to use the models of galactic formation and chemical evolution, on having taken into account the difference in the chemical composition of the stars belonging to the halo, discs, dynamic groups, bulge and bars of the Galaxy.

Co-authors:

• Basak N.Yu., Gorbaneva T.I., Korotin S.A., Soubiran C., Usenko I.A.

• Thank for you attention!

Test: source of production

(37, 44)

r-processes - A >= 56, 1) --massive stars, as supernovae 2)merging of neutron stars (Wanajo, Janka, Muller,

NIC2010)

Burris et al., 2000

r s

Cristallo et al., 2009

[Ba/Y] vs. [Fe/H], [Eu/Y] vs. [Fe/H]