Mass Loss in Evolutionary Models of Low  and Intermediate Mass Stars

1. Mass Loss in EvolutionaryModels of Low and IntermediateMass Stars Paola Marigo Department of Physics and AstronomyG. Galilei University of Padova, Italy

2. outline • Mass loss on the RedGiantBranch • old and new formalisms • old and new methods to probe RGB mass loss • predictedmetallicitydependence • dustformation • Mass loss on the AsymptoticGiantBranch • manydifferentavailableformalisms • impact on evolutionaryproperties (lifetimes, nucleosynthesis, finalmasses) • a global calibrationmethodbased on EPS models of galaxies

3. Mass loss across the H-R diagram Mass loss measurements across the H-R diagram (Cranmer & Saar 2011, ApJ, 741, 54)

4. Mass loss from low- and intermediate- mass stars (0.8 M/M 6-8) Significant mass losstakesplaceduring2 evolutionaryphases, bothalong the Hayashilines: In redgiants, before the onset of large-amplitudepulsation. Typical mass-lossrates are low,  10-8Mʘ/yr. Where: on the RedGiantBranchand Early AGB Mainform of mass loss in the lowest mass evolvedstars, i.e. globular cluster stars. In TP-AGBstarsafter the onset of large amplitudepulsation(Mira). Typical mass-lossrates are large, up to 10-4Mʘ/yr(super-winds) .

5. Mass loss on the RGBWhichis the drivingmechanism? Dissipation of mechanicalenergygenerated in the convection zone? Acoustic or magneticwaves? (Fusi Pecci & Renzini 1975) No definitive theoretical model yet. Usualrecipe: Reimers’ Law for mass loss (Reimers (1975) Basic assumption: the rate of gravitationalenergycarried out in the windisproportional to the stellar luminosity (dimensional scale argument) No physicalinterpretation of the windmechanism adjustableparameter0.350.45

6. A modified Reimers' lawbased on a physical approach (Schröder & Cuntz 2005, 2007) From modelling of mechanicalenergyflux: convectiveturbulence => magnetic+acousticwaves Wind energy balance Mechanicalluminosity Chromosphericradius  =

7. A recenttheoreticalapproach(Cranmer Saar 2011) Wind models for cool MS and evolvedgiantsbased on magnetohydrodynamicturbolence in the convective subsurfacezones. GK dwarfs: windsdriven by gas pressure from hot coronae Redgiants: windsdriven by Alfvénwave pressure ColdAlfvénwaves FA*=Alfvénwaveenergy f*= fillingfactor Hot coronae Schröder & Cuntz (2005) assume dM/dt FA*

8. What are the Hints for Mass Loss on the RGB? • Classical inference (Renzini & FusiPecci 1988) • Typical globular cluster turnoff mass is 0.85 M. • Masses of RR Lyraestars (on the Horizontal Branch, following He core • ignition at the tip of the First Giant Branch) are 0.65 M(from pulsation • theory). • Hence, ~0.20 Mis lost between the main-sequence and the HorizontalBranch. • ~0.20 Mis the mass thatshould be lost to account for the morphology • of the extended blue HorizontalBranchesin the HR diagrams of GGCs. CCG M

9. Multiple populations in CCGs and Heliumcontent NGC 2808 (Z=0.0014, age=10.1 Gyr) Several authors have recently suggested that multiple populations with widely varying levels of He abundance may be present in GCs. The extended blue HB may be explained with high He content. This fact would weaken the RGB mass-loss calibration method based on the HB morphology. Lee et al. (2005, ApJ, 621, L57)

10. Pulsationmodels for 47 Tucvariables: inference of mass loss From theoretical PMR relations Lebzelter Wood (2005) concluded thatobservations of  Tucvariables are recoveredinvoking mass lossoperating on the RGB (Reimers Law) and AGB. A totalamount of . M ejected mass isrequired.

11. Do current RGB prescriptionsoverestimate mass loss Mass lossrates of RGB and AGB stars in GGCs (M, M, M) from chromosphericmodels of the H line Mass loss increases with L and with decreasing TEFF Suggestion of metallicitydependence Rates are ~order magnitude less than ‘Reimers’ and IR results Meszaros et al. 2009

12. Asteroseismology: integrated RGB mass loss Miglio et al. 2012, MNRAS, 419, 2077 Independentconstraints on masses and radii of RGB stars from Kepler data Solarlikeoscillationspectra: frequencyspacing frequency of maximum power NGC 6791: a metalrichold open cluster with FeH and age Gyr  RedGiantBranchstars  RedClumpstars           

13. PredictedMetallicityDependenceon the RGB age Gyr allnomalized to  atFeH Big spread atincreasing Z! Asteroseismologic estimate atage Gyr Kalirai J S , Richer H B Phil. Trans. R. Soc. A 2010;368:755-782

14. Dust or notDuston the RGBA word from theory In between the observationaldebateof Origlia et al. 2010 vs Boyer et al. 2010 (seealsoMomany et al. 2012, Groenewegen 2012) a strong theoreticalconclusionby Gail et al. 2009, ApJ, 698, 1033 Fraction of the element Si condensed into forsterite grains on the tip of the RGB, with maximum possible growth coefficient. Unfavorableconditions of RGB winds: transition to a highly supersonic outflow occurs close to the star where temperatures are too high for dust formation. Condensation factor very low for all initial masses and metallicities, except perhaps for stars of   and 

15. The TP-AGB Phase Dusty circumstellar envelope atmosphere convective envelope energy sources and nucleosynthesis

16. Pulsation: a keyingredient A very rapid rise in Mdot with P to “superwind” values. Then a very slow increase. No information on any mass dependence; large variation at a given P. Derived by fitting dust envelope models to the combinedSpitzer 5-35 micron spectra and simultaneousJHLK photometry (Groenewegen et al. 2007). Based on CO microwaveobservations in the windoutflow(Vassiliadis & Wood 1993)

17. The onset of the Super Wind: a criticalissue The luminosity of termination of AGB evolution(complete envelopeejection) is determined by the period (luminosity) at which Mdot rises rapidly to "superwind" values. Theory: The transition to a superwind is dictated by large amplitudepulsation+ dust + radiationpressure (large L) Observations: The dust-enshrouded AGB stars are all large amplitude pulsators.

18. Mass-Lossrecipes empirical theoretical • Vassiliadis & Wood (1993)[empirical, CO microwave estimates • of Mdot, plotted against pulsation period] • Bowen (1988) and Bowen & Willson(1991) [computed mass • loss rates with simplistic energy loss mechanisms and grain • opacities] • Blöcker (1995) [formula based on Bowen (1988)] • Groenewegen (1998) [C star mass lossrates in solar vicinity] • Wachter et al (2002; 2008) [C star pulsation/mass lossmodels] • Groenewegen et al (2007)[C star mass lossrates in the LMC • and SMC from Spitzer observations] • Van Loon et al. (2005) [O-rich dust-enshrouded AGB and RSG stars in the LMC] • Mattsson et al. (2010)[C star pulsation/mass lossmodels] • O-rich models lacking [see Jeong et al. (2003), and S. Hoefner this workshop]

19. AGB MASS LOSS:impact on evolutionarymodels TP-AGB evolutionaryfeatures are dramaticallyaffected by the adopted mass-lossrecipe: LifetimesDetermines the number of thermalpulses LuminositiesAGB tip, HBB over-luminosity of massive AGB stars FinalmassesLimits the growth of the core mass NucleosynthesisLimits the number and the efficiency of dredge-up episodes; affects theHBB nucleosynthesis

20. Comparingdifferent Mass-lossformalisms: Mi=2.0Mʘ Zi=0.008 Marigo et al. 2012 Vassiliadis & Wood 1993 Bloecker 1995 Vassiliadis & Wood 1993 SW at P=800 days Wachter et al. 2008

21. AGB mass loss and windproperties Vassiliadis & Wood 1993 Vassiliadis & Wood 1993 with SW atP=800 days • Mi=2M • Mi=3M • Mi=4M Models: Nanni et al. 2012, in prep.

22. ChemicalYields Mi.   Yields relative difference: C   other light elements   Fe groupelements up to a factor of 2 Stancliffe Jeffery 2007, MNRAS, 375, 1280

23. Mass Loss and Hot Bottom Burningin a (Mi=5 M Z=0.008) model Bowen & Willson 1991 + Wachter et al. 2008 Vassiliadis & Wood 1993 Marigo et al. in prep.

24. Nucleosynthesis and molecularchemistry Bowen & Willson 1991 + Wachter et al. 2008 Vassiliadis & Wood 1993 Marigo et al. in prep.

25. AGB MASS LOSS: calibratingobservables AGB mass loss can be constrainedcombining accurate evolutionary models with populationsynthesissimulations Lifetimesnumbercounts of AGB stars in star clusters and galaxyfields Luminositiesluminosity, color, and period distributions Central star’s mass (WD)initial-final mass relation and WD mass distribution NucleosynthesisM-C transition L in clusters, (3° dredge-up and HBB) C/O values, Li-rich AGB stars PN abundances test test test test

26. standard CALIBRATORS: agb STARSIN Magellanic CLOUDS’ CLUSTERS • Vassiliadis & Wood 1993 Marigo et al. 2012

27. standard CALIBRATORS: agb STARSIN Magellanic CLOUDS’ CLUSTERS • Vassiliadis & Wood 1993 • Bloecker 1995 Marigo et al. 2012

28. standard CALIBRATORS: agb STARSIN Magellanic CLOUDS’ CLUSTERS • Vassiliadis & Wood 1993 • Bloecker 1995 • Bowen & Willson 1991 (C/O<1) • Wachter et al. 2008 (C/O>1) Marigo et al. 2012

29. standard CALIBRATORS: agb STARSIN Magellanic CLOUDS’ CLUSTERS • Vassiliadis & Wood 1993 • Bloecker 1995 • Bowen & Willson 1991 (C/O<1) • Wachter et al. 2008 (C/O>1) • Van Loon et al. 2005 (C/O<1) • Wachter et al. 2008 (C/O>1) Marigo et al. 2012

30. standard CALIBRATORS: agb STARSIN Magellanic CLOUDS’ CLUSTERS • Vassiliadis & Wood 1993 • Bloecker 1995 • Bowen & Willson 1991 (C/O<1) • Wachter et al. 2008 (C/O>1) • Van Loon et al. 2005 (C/O<1) • Wachter et al. 2008 (C/O>1) • Kamath et al 2011 (C/O>1) • VW93 + SW delayedat P=800 days Marigo et al. 2012

31. standard CALIBRATORS: agb STARSIN Magellanic CLOUDS’ CLUSTERS • Vassiliadis & Wood 1993 • Bloecker 1995 • Bowen & Willson 1991 (C/O<1) • Wachter et al. 2008 (C/O>1) • Van Loon et al. 2005 (C/O<1) • Wachter et al. 2008 (C/O>1) • Kamath et al 2011 (C/O>1) • VW93 + SW delayedat P=800 days • Vassiliadis& Wood 1993 (C/O<1) • Arndt et al. 1997 (C/O>1) Marigo et al. 2012

32. A new calibration approach: ANGSTthe ACS Nearby Galaxy Survey Treasury (Dalcanton et al. 2009; Girardi et al. 2010) • High accuracy optical multiband photometry of 62 galaxies outside the Local Groups (within 4 Mpc). • 12 selected galaxies: metal poor [Fe/H] -1.2 • and dominated by old stars, with ages > 3 Gyr • (0.8 M⊙ Mi1.4 M⊙). • Derivation of SFH from CMD fitting based on Marigoet al. (2008) isochrones.

33. AGB stars in the ANGST galaxies • RGB and AGB stars detected • Counts of AGB stars brigther than the RGB tip • Typically NAGB60 - 400 per galaxy • NAGB/NRGB0.023 – 0.050 • Simulations of galaxies:TRILEGAL (Girardi et al.2005) • multi band mock catalogues of resolved stellar populations, for given distance, SFR, AMR

35. Observations vsModels Predicted AGB stars too many too bright

36. Curing the discrepancy:more efficient mass loss on the AGBat low Z and old ages Schroeder & Cuntz 2005 + Bedjin (1998) like dust-driven mass loss Shorter TP-AGB lifetimes Fainter luminosiites Lower final masses (WDs) White Dwarf mass measurements in M4 (Kalirai et al. 2009, ApJ, 705, 408)

37. beforeafter

38. SNAP-11719(Dalcanton et al. 2011, ApJS, 198, 6) snapshotsurvey of 62 galaxies(26 observed) with the near IR filtersWFC3/IR F110W+F160W SFH from optical CMDs Complete census of AGB stars from near IR

39. SNAP-11719:snapshot survey of 62 galaxies(26 observed) with the near IR filters WFC3/IR F110W+F160W(Dalcanton et al. 2011, ApJS, 198, 6) rCHeB bCHeB AGB MS RGB SFH from optical CMDs Complete census of AGB stars from near IR

40. Melbourne et al. 2012, ApJ, 748, 47 RGB + AGB stars responsible for 21% + 17% of the integrated flux emitted by galaxies in the near IR Present TP-AGB models show an average excess: 50% in the predicted lifetimes, • factor of 2 in the emitted flux • ODD! • Models are calibrated on direct counts of AGB stars in MC clusters. Possible relevant impact in EPS models of galaxies and mass determination of high-z objects (Bruzual 2009).

41. The InitialFinal Mass Relation:Dependence on Mass-LossEfficiency

42. The InitialFinalMass Relation:The 3° dredge-up plays a role! Mc = Mf-Mc,1tp alowerlimitto the effective nuclearfuelburnt (hencelifetime) during the TP-AGB. Presentmodels of intermediate mass AGB starspredict a veryefficient 3° dredge-up (), with practically no growth of Mc (Karakas et al. 2010, Stancliffe et al. 2009).

43. The InitialFinal Mass Relation:Dependence on Metallicity Marigo  Girardi 2007 Karakas 2010 Non monotonic trend with Z Monotonic trend with Z

44. Concludingremarks • RGB mass loss • The classicalmethodology (Reimers law + HB morphology in GGCs) iscurrentlydebated due to • Alternative, more physically sound, mass-lossprescriptions • new scenario of GGCs: multiple stellar populations and He content • new observational/theoreticaltechniques (asteroseismology, pulsationmodels, infrareddata) • From theory: tiny, ifnotany, amount of dust on the RGB atsubsolar Z • AGB mass loss • Onset of the superwind, a criticalpointstilluncertain (M, Z, C/O, L, Teff, P) • Evolutionarypropertiesheavilyaffected by the adopted mass-loss law • Initial-final mass relation: mass loss and thirddredge-up bothconcur to shapeit. • Calibrationneeded! Populationsynthesis of AGB stars in clusters and • in fields of galaxies, covering a large range of ages and metallicities. • Ongoing work.