PoS(FRAPWS2016)027 https://pos.sissa.it/ ∗ -elements, Fe and heavier. The main observables and in particular the chemical abun- α [email protected] [email protected] [email protected] [email protected] eaker. We will discuss some highlights concerning the chemicalFirst evolution we of our will Galaxy, describe the the Milky main Way. of ingredients the necessary Milky to Way. build Then we a will model illustratenucleosynthesis for some and the Milky compute chemical Way models the evolution which evolution includes of detailed aN, stellar large O, number of chemical elements, including C, dances in stars and gasfinally will some conclusions be from considered. this astroarchaeological A approach will comparison be theory-observations derived. will follow and Sp ∗ Copyright owned by the author(s) under the terms of the Creative Commons ipartimento di Fisica, Università di Trieste E-mail: Emanuele Spitoni Dipartimento di Fisica, Università di Trieste E-mail: Donatella Romano I.N.A.F. Osservatorio Astronomico di Bologna E-mail: Alvaro Rojas-Arriagada Instituto de Astrofísica, Facultad de Física,Mackenna Pontificia Universidad 4860, Santiago, Católica de Chile Chile, Av.Millennium Vicuña Institute of Astrophysics, Av. VicuñaChile Mackenna 4860, 782-0436 Macul, Santiago, E-mail: Frontier Research in Astrophysics - II 23-28 May 2016 Mondello (Palermo), Italy D Francesca Matteucci The chemical evolution of the Milky Way © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). PoS(FRAPWS2016)027 - α (2.1) /Fe] versus [Fe/H] Francesca Matteucci α -elements and iron. The α : i) initial conditions, ii) the model results compared to the is therefore very important to t al. 2013), LAMOST (Cui et l. 2012), APOGEE (Majewski , He, D, Li), while all the other terpretation we are able to estab- ow different abundance patterns, z et al. 2006), SEGUE-1 (Yanny ng a very large number of Galactic will born. This is the chemical evo- oposed in the last 40 years and have ample ork of Beatrice Tinsley (1941-1981) r example, the [ (see Matteucci 2012 for a review on hemical evolution describes how the sons we will derive the timescales for al elements, as well as how important rent morphological type. As it is well tantaneous recycling approximation to ate galactic components, such as halo, e most common parametrization of the will concentrate on the evolution of the SNe, whereas Fe is produced on longer s constraints on stellar nucleosynthesis. trends as due to the different timescales ased chemical abundances for hundreds f the “time-delay model”, which allows FR) and the initial mass function (IMF), d their components, and this approach is d abundance patterns. Galactic chemical supernovae (SNe) to the chemical enrich- through the chemical abundances we can , 4 . 1 gas νσ 2 )= t ( 12) were built inside the stars: stars produce chemical ψ > A In the last years a great deal of spectroscopic data concerni The main ingredients to build a chemical evolution model are stars has appeared in the literature.thousands Many surveys of have stars rele in theet Galaxy: al. for 2009), example SEGUE-2 RAVE (Rockosial. (Steinmet et 2012), al. Gaia-ESO 2009), (Gilmore ARGOSet et (Freeman al. al. e 2012), 2015) GALAH andconstruct (Zucker the theoretical et AMBRE models a able project to (de reproduce the Laverny observe et al. 2013). It Milky Way 1. Introduction evolution models had a great start thanks to the pioneering w who established the basis ofgas this and its important chemical field. composition evolveknown, Galactic in during c galaxies the of Big diffe Bangspecies only from light carbon elements (elements were with formed (H elements are produced on short timescales bytimescales core-collapse (with a delay) by Typelish Ia SNe. the timescales By means of of the such formationdisk an of and in galaxies bulge and in of the Milky separ indicating Way. different The stars histories in of each starinfer component formation. the sh formation In and evolutionary fact, historyknown of as galaxies “astroarchaeological an approach”. In thisMilky paper, we Way and on what we havemost learned important up and to recent now. observations. We will Fromthe present these formation compari of the different Galactic components as well a 2. The chemical evolution model for the Milky Way history of star formation, namely theiii) star the formation rate stellar (S yields, iv) gasSFR flows is in that and of out Kennicutt the (1998), galaxy. that Th we also adopt: relation and how it isthe expected subject). to The time-delay vary model in interpretson different the which galaxies observed different chemical elements are produced, as for ex elements and restore them into the ISM,lution out process. of Many which chemical new stars evolution modelsdemonstrated have how been important is pr to relaxcompute the hypothesis the of evolution ins of the abundancesare of the different relative chemic contributions of Type Ia andment. core-collapse In particular, it hasus been to established interpret the principle the o abundance patterns measured in stars: fo PoS(FRAPWS2016)027 ∼ per J M in C-O white c chemical enrich- Francesca Matteucci 30. If the explosion < N and heavy s-process masses of such elements ⊙ produce the present time companion is a low mass they are known as “core- aw. The most commonly M / ow or intermediate mass star Li. For these stars, which end M o contribute to other elements, al amount of iron (0.6 7 oss along the giant and asymp- odels for rotating massive stars i, Fe, Cu and Zn. As for the He rakas (2010). criptions are from Iwamoto et al. < iptions and the implementation of detailed description of the adopted oupa et al. (1993), Kroupa (2001), distinguish between different mass of stars with masses larger than edients for chemical evolution, the e described below. work, we adopt the same nucleosynthe- ations by Kobayashi et al. (2006) for the ), which are divided in single stars and J M -8 3 J M erg, hypernova events may occur (SNe Ic). For core- 51 ). J M 8 > Type Ia SNe are thought to originate from carbon deflagration The single stars in this mass range contribute to the galacti is the efficiency of star formation and it should be tuned to re ν event) and non negligible quantities ofsuch Si, as S O, and C, Ca. Ne, Theyejected als Mg, by but massive in stars. negligible The adopted amounts(1999). nucleosynthesis compared pres to the dwarfs in binary systems. Type Ia SNe contribute a substanti Type Ia SNe. their lives as white dwarfs, we adopt the prescriptions of Ka binary systems. Binary systems formed bycompanion a white can dwarf originate and a either l Typestar), Ia SNe or novae (when the massive stars (M ment through planetary nebula ejection andtotic quiescent giant mass branches. l elements. They They enrich can the also produce ISM non-negligible mainly amounts of in He, C, and low- and intermediate-mass stars (0.8 Single stars. , whereas SNe II originate from stars in the mass range 8 Massive stars are the progenitors of Type II, Ib and Ic SNe and For chemical evolution models, the nucleosynthesis prescr ⊙ • • • • M Milky Way where collapse SNe”. In particular,30 the SNe Ib,c are the explosion 2.1.2 Massive stars energies are significantly higher than 10 collapse SNe, we adopt up-to-date stellar evolution calcul and CNO elements, we take(see into Romano account et al. the (2010) results for of references). Geneva m following elements: Na, Mg, Al, Si, S, Ca, Sc, Ti, Cr, Mn, Co, N SFR in the objectadopted one IMFs are is the modeling. oneChabrier of Salpeter The (2003). (1955), IMF Scalo The is (1986),nucleosynthesis Kr normally stellar prescriptions we a yields will power are adopt in l very our model important ar ingr 2.1 Nucleosynthesis prescriptions the yields in the model are fundamentalsis ingredients. prescriptions In of this model 15 ofyields Romano can et be al. found. (2010), whereAs a regard to the computationranges, of as well the as stellar single yields, stars versus one binary has systems: to 2.1.1 Low- and intermediate-mass stars PoS(FRAPWS2016)027 Francesca Matteucci for star formation is 2 − pc ⊙ M n suggested for the Milky Way d above (continuous line) as well Recchi, 2001). The IMF adopted pisode occurring on much longer olar vicinity. Results and figure from formation between the end of the ick and thin disk, are based on the y systems, in particular the single- , whereas there are some elements assume that the halo and thick disk d separately from the halo and thin rring on a timescale no longer than del”. In this scenario, the halo formed orming on a timescale of 7 Gyr. The ano et al. (2010). It is clear from Figure t sets of yields. The best set is that represented escribed here. The adopted IMF in both cases is 4 Predicted and observed [X/Fe] vs. [Fe/H] relations for the s Another model, after that of Chiappini et al. (1997), has bee In Fig.1 we show the results obtained for the yields discusse The results we will present relative to the Galactic halo, th as for older sets of yields (dashed1 line), as that discussed the in Rom trend ofwhose some yields chemical should be elements strongly is revised well (i.e. reproduced K, Sc, Ti). (Micali et al 2013), wheredisk the formation. thick This disk model phase has been was called considere “three-infall mo by the solid lines withthat the of nucleosynthesis Kroupa prescriptions et al. d (1993). Romano et al. (2010).The model results refer to two differen Figure 1: Milky Way 2.2 The model for halo and disks two-infall model of Chiappini etformed al. out (1997). of In a this2 relatively model fast we Gyr, whereas episode the of thin gastimescales: disk accretion an formed occu inside-out out formation ofassumed with another progenitors the for accretion solar Type e Ia region SNedegenerate f are model white (see dwarfs Matteucci in & binar Greggiofor 1986; halo Matteucci and & disks is the Scalo (1986) one. A gas threshold of 7 assumed. This threshold produceshalo-thick disk naturally phase a and the gap thin in disk phase. the star PoS(FRAPWS2016)027 Francesca Matteucci -enhanced should have α e-infall model, compared to ed with data. The predictions for , we can conclude that the halo tars (Hayden et al. 2015; Rojas- escale of 1-2 Gyr, no longer, as e thick and thin disk stars are clearly accretion episode forming the thick ars, being sk stars is not evident, so that strong n function peaked at higher metallic- n Figure 3 we show some recent data k and thin disk star data are indicated he bulge stars formed faster than those alactic bulge contains two main stellar ally, as in the model described above. e those for the thin disk. A comparison with ooks like if the thick and thin disk formed d metal poor and b) a metal rich population 2 Gyr) ∼ -elements relative to Fe, and the thin disk in the α 5 The [O/Fe] vs. [Fe/H] predicted by Micali et al (2013) compar The Galactic bulge shows a stellar metallicity distributio In Figure 2 we show the predicted [O/Fe] vs. [Fe/H] by the thre From the models presented above and comparison with the data Recently, many data have appeared on the thick and thin disk s ity than the G-dwarfs in thein solar the vicinity. solar This vicinity. means that Hillpopulations: t et a) al. a (2011) classical bulge suggested stellar that population the calle G solar vicinity formed on a much longer timescale (7 Gyr). 2.3 The Galactic bulge Figure 2: Milky Way very fast during a first accretion episode, then followed the disk, on a time scale short but longer than the halo ( formed in a faster process than the thin disk stars. data relative to the halo,in thick the and Figure thin but disk. aconclusions clear The separation cannot halo, between thic be thick and derived, thin except di that the thick disk st formed on a timescale ofproven less by the than observed 1 enhanced Gyr, abundances the of thick disk on a tim on two different timescales but in parallel and not sequenti Arriagada et al. 2017) wherefrom a Gaia-ESO clear survey (Rojas-Arriagada separation et is al. evident.separated 2017) in where I the th plot [Mg/Fe] vs. [Fe/H]. In particular, it l the two-infall model (green line) is also shown. the halo are in red, those for the thick disk in black and in blu PoS(FRAPWS2016)027 Francesca Matteucci hus confirming pre- and timescale of gas 0 1 . 5 − . 18 . .665 Gyr = 6 5 1 25 . p ia-ESO data from Rojas-Arriagada he model results of Grieco et al. = how these data together with the /N 2 gada et al. (2017) compared to model ν tic bar or be inner disk stars. The 0 0 χ Cescutti et Matteucci 2011; Grieco . rom high-resolution, high-S/N spec- 0 015, Zoccali et al 2017, GIBSsurvey; cy 0 0 for the main population (the endemic . t al 2017,APOGEE survey, in contrast opulation, as described in Grieco et al. 0 alpeter IMF, as described in the text. isk are evident from the Figure. 5 bution function for bulge stars, where there is . 5 0 . 0 − − 6 time (Gyr) [Fe/H] (dex) [Fe/H] (dex) 0 . 1 − Disp=0.09 0 . 1 5 − . 1 Model Data − 0.015 0.018 0.023 0.032 0.049 0.079 0.132 0.216 0.329 0.472 0 Bias=-0.05 0 Thick (3246) Thin (3067) 5 . . 2 1 4 2 0 2 4 8 6 4 2 0 4 2 . . . . . − 6 5 4 3 2 1 0 1 2 ...... − 0 0 0 0 0 ......

0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 − −

− Residuals − − −

M/e (dex) [Mg/Fe] M/e (dex) [Mg/Fe] 1 Gyr. As one can see, the model prediction fits well the data, t . 0 = τ [Mg/Fe] vs. [Fe/H] in stars in the thick and thin disks from Ga [Mg/Fe] vs. [Fe/H] in Galactic bulge stars from Rojas-Arria et al. (2017). The two parallel sequences for thin and thick d Figure 4: Figure 3: Milky Way vious papers (Matteucci & Brocatoet 1990; al. Ballero et 2012) al. suggesting 2007; ametal-poor classical very one). fast The bulge stellar formation, metallicity distri atevidence of least two populations (Hill etRojas-Arriagada al 2014,2017, 2011; Gonzalez Gaia-ESO et survey; al Schultheis 2 e with Ness et al 2013, ARGOS survey) is shown in Figure 5, with t accretion predictions. The model assumes a fast bulge formation and a S which can be the resultmost of recent star data formation on abundance induced ratiostroscopic by in data) the bulge are Galac stars from (coming the f prediction Gaia-ESO of survey. a bulge In model Figure relative(2012), 4 to assuming we the a very classical s fast bulge SFR p with star formation efficien PoS(FRAPWS2016)027 Francesca Matteucci quickly, although on ctated by the large overabun- tocentric distance cannot pre- ve appeared in the past years. 1). It is clear from the comparison and O, B stars that the model with dial gas flows are important for the scales for the formation of the vari- on without a gas threshold for star am) are from Hill et al. (2011); models reasonable agreement with the data, Figure 6. For the outermost regions Schoenrich & Binney 2009; Spitoni we can suggest the following: o do that one compares the predicted sk. Other important parameters are: i) l gas flows can in principle produce a efers to the so-called metal poor classical d best reproduces the observed gradient. as threshold for star formation. In Figure o the metal rich population. [Fe/H] 7 -1 0 1 0 0.1

0.15 0.05 tot N/N -elements observed in halo stars. The thick disk also formed α Two stellar population in the Galactic bulge. Data (histogr dances of Different models for the evolution of the entire thin disk ha Models with a constant timescale of gas accretion with galac Galactic astroarchaeology is a useful tool to infer the time 1. The halo phase lasted no longer than 0.5-1.0 Gyr. This is di (curves) are from Griecobulge et population, al. while the (2012). black continuous The curve refers red t dashed curve r 2.4 Abundance gradients along the Galactic disk These models include radial gas& flows Matteucci and 2011; stellar Spitoni migration et al. ( creation 2015; of an Kubryk abundance et gradient al. in 2015).the the inside-out Ra gas formation along of the the thin disk, di ii)6 the we existence show of the a g gradients predictedwith by O Spitoni abundance & measured Matteucci in (201 inside-out HII formation regions, and radial planetary gas nebulae flows with variable spee ous Galactic components: halo, thick,and thin observed disk abundance and patterns. bulge. From the T discussion above dict any gradient. Models withoutgradient. inside-out but On with the radia otherformation hand, and a radial gas model flows withbut can inside-out only still formati for produce a the gradient verythere in inner is disk practically regions, no as gradient. it is evident from 3. Summary and Conclusions Figure 5: Milky Way (2012) compared to the observations. PoS(FRAPWS2016)027 -elements α Francesca Matteucci considering APOGEE data ts along the Galactic thin disk. inside-out. In particular, the we would not expect any halt verabundances of the star formation at the end of that the thick disk is the result .3-0.5 Gyr, at least the bulk of da et al. 2017) seem to suggest lar region took at least 7 Gyr, as he early part of the Milky Way two disks should be the same as roduced if a timescale no longer rmation of the halo and thick disk -dwarfs, and the outermost regions tion of stars whose formation was 11). The black continuous line is the result isk formation and gas threshold in the star ith variable speed. This model is clearly the adial flows at constant speed (1 km/sec) and 8 14 kpc) over 10 Gyr. Comparison between data and models about abundance gradien > R a longer timescale than the halo. Also thick disk stars show o and their metallicity distribution functionthan 2 can Gyr be is well assumed (Micali rep et al. 2013). inner regions formed on timescales of 1-2suggested Gyr, whereas by the the so metallicity distribution function of the G ( and between the thick and thin disk. Haywood et al. (2016), by (Hayden et al. 2015), concluded thatthe there was thick a disk quenching phase. in Kubrykof et stellar al. migration: (2015) suggested theydisk. instead concluded Very that recent data the from thick Gaia-ESOthat disk survey the (Rojas-Arriaga is thick t and thinin disk the formed star in formation, parallel. but the Insuggested timescales such above. of a formation case of the its stars, the classical bulge stellar population. A popula 2. The thin disk instead formed on a much longer timescale and 3. Probably the star formation stopped briefly between the fo 4. The Galactic bulge formed very quickly, on a timescale of 0 of a model without radial gas flows but including inside-out d References to the data can be found in Spitoni &formation. Matteucci The (20 red short-dashed linethe is blue long-dashed the line same is model the with same r model with radial flows w best one. Figure 6: Milky Way PoS(FRAPWS2016)027 Francesca Matteucci endemic metal-rich bulge stars galactocentric distance (Spitoni ge) is present, outnumbering at the lt of the inside-out formation of the ., 2006, ApJ, 653, 1145 metallicity distribution is showing in , 545 a. H., Hix W. R., Thielemann F. K., 1999, A, 589, A66 7 ssenger, 147, 25 RAS, 428, 3660 80, A126 &A, 584, A46 , 808, 132 &A 467, 123 13, The Messenger, 153, 18 , 765 ringer-Verlag, Berlin eis, M., Babusiaux, C., Royer, F., Barbuy, B. et l. 2015, arXiv:1509.05420 2, A&A, 548, 60 9 triggered by the bar (those participating inmetal-rich the part X-shape of bul the bulge MDFbelonging a to possibly the small initial fraction classical of population. The stellar fact a bimodal distribution. thin disk coupled with radial flows with a speed variable with & Matteucci, 2011). al. 2011, A&A, 534, 80 ApJS, 125, 439 5. Finally, Galactic abundance gradients can arise as a resu [2] Cescutti, G. and Matteucci, F. 2011,[3] A&A, 525, 126 Chabrier, G. 2003, ApJ 586, L133 [4] Chiappini, C., Matteucci, F., Gratton, R.[5] 1997, ApJ, 477 Cui, X.Q., Zhao, Y.H., Chi, Y.Q., et[6] al. 2012, de RAA, Laverny, 12, P., Recio-Blanco, 119 A., Worley, C.C., et al. 20 [9] Gonzalez, O. A., Zoccali, M., Vasquez, S., et al., 2015, A [1] Ballero, S. Matteucci, F., Origlia, L., Rich, R.M. 2007 A [7] Freeman, K., Ness, M., Wylie-de-Boer, E., et[8] al. 2013, Gilmore, MN G., Randich, S., Asplund, M., et al. 2012, The Me Milky Way References [10] Grieco, V., Matteucci, F., Pipino, A., Cescutti,[11] G. 201 Hayden, M.R., Bovy, J., Holtzman, J.A.,[12] et al. 2015, Haywood, ApJ M., Lehnert, M.D., Di Matteo,[13] P. et al. Hill, 2016, V., Lecureur, A& A., Gómez, A., Zoccali, M., Schulth [14] Iwamoto K., Brachwitz F., Nomoto K., Kishimoto N., Umed [21] Majewski, S.R., Schiavon, R.P., Frinchaboy, P.M., et[22] a Matteucci F., 2012, Chemical Evolution of[23] Galaxies. Sp Matteucci, F. and Brocato, E., 1990,[24] ApJ, 365, 539 Matteucci, F. and Greggio, L., 1986, A&A, 154, 279 [15] Karakas A. I., 2010, MNRAS, 403,[16] 1413 Kennicutt, R. C., Jr, 1998, ApJ,[17] 498, 541 Kobayashi C., Umeda H., Nomoto K., Tominaga N., Ohkubo T [18] Kroupa, Pavel, Tout, C. A., Gilmore, G.[19] 1993, MNRAS, Kroupa, 262 P. 2001, MNRAS, 322, 231 [20] Kubryk, M., Prantzos, N., Athanassoula, E. 2015, A&A, 5 PoS(FRAPWS2016)027 Francesca Matteucci Milky Way, 458, 421 sics Decadal Survey , arXiv:1704.03325 1648 n, J., & Hermes Team 2012, Galactic , A&A, 522, A32 37, 4377 NRAS, 430, 836 A&A, 599, A12 isenstein, D., 2009, in ArXiv Astrophysics ApJ, 802, 129 E., et al., 2017, A&A, 600, A14 , Mikolaitis, S., Matteucci, F., Spitoni, E., , 132, 1645 ., 2014, A&A, 569, A103 10 Schultheis, M., Hayden, M., Hill, V., Zoccali, M. et al. 2017 Archaeology: Near-Field Cosmology and the Formation of the e-prints, Vol. 2010, astro2010: The Astronomy and Astrophy [32] Salpeter, E.E. 1955, ApJ , 121,[33] 161 Scalo, J.M. 1986, Fund. Cosmic Phys.,[34] 11, 1 Schoenrich, R. and Binney, J. 2009,[35] MNRAS, 396, 203 Schultheis, M., Rojas-Arriagada, A., García Pérez, A. [31] Romano, D., Karakas, A. I., Tosi, M., Matteucci F., 2010 [36] Spitoni, E., Romano, D., Matteucci, F. Ciotti, L. 2015, [40] Zoccali, M., Vasquez, S., Gonzalez, O.[41] A., et al., Zucker, D. 2017, B., de Silva, G., Freeman, K., Bland-Hawthor [37] Spitoni, E. and Matteucci, F. 2011,[38] A&A, 531, 72 Steinmetz, M., Zwitter, T., Siebert, A.,[39] et al. 2006, Yanny, B., AJ Rockosi, C., Newberg, H.J., et al. 2009, AJ, 1 Milky Way [25] Matteucci, F. and Recchi, S. 2001,[26] ApJ, 558, Micali, 351 A., Matteucci, F., Romano, D. 2013, MNRAS, 436, [27] Ness, M., Freeman, K., Athanassoula, E.,[28] et al., Rockosi, 2013, C., M Beers, T.C., Majewski, S., Schiavon, R., E [29] Rojas-Arriagada, A., Recio-Blanco, A., Hill, V., et[30] al Rojas-Arriagada, A., Recio-Blanco, A., de Laverny, P.