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Abundances in Large Magellanic Cloud Star Clusters

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Abundances in Large Magellanic Cloud Star Clusters ABUNDANCES IN LARGE MAGELLANIC CLOUD STAR CLUSTERS Summary prepared by Jarrod Hurley, CSPA, Monash November, 2003. ... but first some self-indulgent dynamical stuff ... HST Study of LMC Globular Clusters* * true Globular Clusters Name log(age) [Fe/H] log(Mass) Rg defined as PopII (no gas, NGC1805 7.0 -0.2 3.5 3.7 dust or young stars; low NGC1818 7.4 -0.2 4.1 3.4 metals) halo objects ... ~13 in LMC. NGC1831 8.5 -0.3 4.7 4.6 NGC1868 8.7 -0.6 4.5 5.4 NGC2209 9.0 -0.5 5.0 5.7 Hodge14 9.3 -0.7 4.2 4.4 Hodge11 10.2 -2.1 5.5 5.0 NGC2210 10.2 -2.0 5.5 5.2 4rich clusters at all stages of evolution 495 HST orbits in Cycle 7 (comp. 1998) 4study long-term effects of stellar dynamics and evolution 4investigate IMF and binary populations (Elson et al. 1998; Beaulieu et al. 1999) Core -Radius Evolution (Mackey & Gilmore 2003) ... different IMFs? 4factor of 5 required in slope 4 NO (see de Grijs et al. 2002) ... different orbits? ... different binary fractions? 4NO 4YES but NO (see Wilkinson et al. 2003) ... maybe star formation efficiency? 4low SFE leads to rapid expansion 4low central density clusters with large Rc (see Wilkinson et al. 2003) Binary Fractions and Mass Segregation 4NGC1818 (40 Myr) (see Elson et al. 1998) models dynamical origin observed binaries segregated ... not primordial Age Spreads in Young Clusters 4NGC 1818 & 1805 4evidence for age spread near turn-off w clues for star formation timescales wimplications for SFE 4complicated by Be stars (many) and blue stragglers (few) (see Johnson et al. 2001) 4binaries give single-age spread (25 Myr best fit) 4overall best fit from 25 + 40 Myr combination simulation 25 Myr Z = 0.02 LMC Chemistry x rapid enrichment phase > 10 Gyr ago x chemical quiescence until 2 Gyr ago x enrichment phase ongoing Olszewski et al. (1991) w spectra of 150 giants in ~80 LMC clusters w [Fe/H] from calibration of Ca triplet line 4most clusters 0.5 - 3 Gyr 4no clusters 3 - 10 Gyr 4abundances for inner & outer Fig 11 here clusters nearly identical star formation not possible in outer LMC now (low gas r) but must have been 2 Gyr ago Dirsch et al. (2000) 4 LMC age-metallicity relation from various sources CMDs for young and intermediate age clusters (Brocato et al. 2001) one old cluster (Mighell, Rich, Shara & Fall 1996) and an old one, i.e. a globular Smith et al. (2002) w C, N, O, Na, Sc, Ti, Fe in 12 LMC red giants (3 in clusters) w [Na/Fe] & [Ti/Fe] consistently lower than Galactic values (-0.1 & -0.5) w [Sc/Fe] ok w [O/Fe] lower than Galactic by 0.2 dex 4agrees with MS B stars (Korn et al. 2002 - young clusters) Fig 10 here 4agrees with OB stars (Rolleston et al. 2002 - field) 4lower values indicate lower SN rate with a lower ratio of Type II to Type Ia w LMC giants show evidence of 1st DU CN-cycling 4N14 up by 0.4 to 0.8; C12 down by 0.3 to 0.5 w no evidence for 2nd DU or HBB w C12/C13 with mass shifted down compared to Galaxy 4owing to increased mixing for low metallicity giants? 4one (of two) NGC 2203 stars has high ratio and maybe AGB dredge-up has begun Fig 9 here (more luminous star) Cunha, Smith, Lambert & Hinkle (2003) w Fluorine abundances measured for: LMC - 9 giants (2 in NGC 2203) w Cen - 2 giants + Galactic field K & M giants w [F/O] abundance ratio declines as metallicity decreases 4low [F/O] in w Cen suggests AGB stars do not play a dominant role in chemical evolution of F 4at odds with large s-process abundances in more metal-rich Fig 4 here w Cen stars 4results consistent with F19 production via either WR winds or n-processes during Type II SNe Rolleston, Trundle & Dufton (2002) w spectra of 5 OB-type MS stars in LMC w differential analysis relative to Galactic comparison stars 4 general metal deficiency of -0.31 +/- 0.04 dex 4no significant variations between cluster and field stars 4 lower [O/Fe] ratio by 0.14 dex 4over-deficiency of Mg relative to other a-elements deep-mixing episodes during giant phase of low to intermediate mass stars may contribute to this, in the absence of massive star formation for ~6 Gyr in LMC LMC Clusters with Measured Stellar Abundances NGC 2004 40 Myr 4 MS B CNO Korn et al. 2002 NGC 1818 40 Myr 1 MS B CNO Korn et al. 2002 5 giants C Meliani et al.1994 NGC 2214 100 Myr 1 AGB Li Maceroni et al. 2002 NGC 1866 150 Myr 9 AGB Li Maceroni et al. 2002 NGC 2031 150 Myr 6 AGB Li Maceroni et al. 2002 NGC 2107 250 Myr 1 AGB Li Maceroni et al. 2002 NGC 1866 100 Myr 3 giants O,Al,Na Hill et al. 2000 NGC 1978 1 Gyr 2 giants O,Al,Na Hill et al. 2000 ESO 121 9 Gyr 2 giants O,Al,Na Hill et al. 2000 NGC 2210 15 Gyr 3 giants O,Al,Na Hill et al. 2000 NGC 1898 13 Gyr 2 giants CNO Smith et al. 2002 NGC 2203 1 Gyr 2 giants CNO Smith et al. 2002 F Cunha et al. 2003 + Fe in many clusters Meliani, Barbuy & Richtler (1994) w C, Fe for 5 giants in NGC 1818 Note: B26 suspected to be binary uncertainty in [C/Fe] is +/- 0.4 w carbon is not over-deficient 4[C/H] ~ -0.7 for LMC HII regions and field stars w mean metallicity [Fe/H] = -0.9 considerably lower than the -0.3 for LMC field 4NGC 1818 formed in a “bubble” where very little enrichment from Type Ia SNe occurred Korn et al. (2002) w CNO (+Mg,Si) from MS B stars in NGC 2004 4no intracluster abundance anomalies 4Si higher in stars than nebular 4LMC nitrogen deficient by 0.5 dex compared to Galactic thin disk Cunha et al. (2003) Fluorine Smith et al. (2002) CNO, etc. Maceroni et al. (2002) w Li during AGB evolution in young LMC clusters w NGC 1866 and 2031 4150 Myr w Look for weak Li (early AGB) then Li destruction , then strong Li (HBB) and then more depletion 4AGB Li cycle evident 4early AGB stars in NGC 1866 (red points) show Li abundance ~ constant with L consistent with Li dilution but ... average log N(Li) = 0 which implies stronger than standard dilution 4cool luminous stars show both absence of Li and strong Li, i.e HBB Hill, Francois, Spite, Primas & Spite (2000) w 10 giants in 4 clusters spanning all ages w Fe, O, Al + inferences on Na (see also Spite et al. 2001) old clusters 4O-Al anti-correlation (?) 4star with lowest O does have high Al (and Na) Ne-Na & Mg-Al cycles + mixing 4LMC old cluster giants clearly (?) follow Galactic behaviour Maybe more in the near future ... Hill 2003 and Johnson 2003 abstracts here References w Elson, Sigurdsson, Davies, Hurley & Gilmore, 1998, MNRAS, 300, 857 w Beaulieu, et al., 1999, in IAU Symp. 190, p.460 w Mackey & Gilmore, 2003, MNRAS, 338, 85 w de Grijs, et al., 2002, MNRAS, 337, 597 w Wilkinson, Hurley, Mackey, Gilmore & Tout, 2003, MNRAS, 343, 1025 w Johnson, et al., 2001, MNRAS, 324, 367 w Olszewski, Schommer, Suntzeff & Harris, 1991, AJ, 101, 515 w Dirsch, Richtler, Gieren & Hilker, 2000, A&A, 360, 133 w Brocato, Di Carlo & Menna, 2001, A&A, 374, 523 w Mighell, Rich, Shara & Fall, 1996, AJ, 111, 2314 w Smith, et al., 2002, AJ, 124, 3241 w Cunha, Smith, Lambert & Hinkle, 2003, AJ, 126, 1305 w Rolleston, Trundle & Dufton, 2002, A&A, 396, 53 w Meliani, Barbuy & Richtler, 1994, A&A, 290, 753 w Korn, Keller, Kaufer, Langer, Przybilla, Stahl & Wolf, 2002, A&A, 385, 143 w Maceroni, Testa, Plez, Garcia Lario & D’Antona, 2002, A&A, 395, 179 w Hill, Francois, Spite, Primas & Spite, 2000, A&A, 364, L19 w Spite, Hill, Primas, Francois & Spite, 2001, New AstR, 45, 557.
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