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The GRAMS Evolved Star Mass-Loss Models: CMDs, CCDs, and Stellar Population Analysis for the LMC

The GRAMS Evolved Star Mass-Loss Models: CMDs, CCDs, and Stellar Population Analysis for the LMC. Benjamin Sargent Collaborators: S. Srinivasan, M. Meixner, SAGE, and SAGE-Spec teams Mass-Loss Return from Stars to Galaxies Workshop May 20, 2010.

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The GRAMS Evolved Star Mass-Loss Models: CMDs, CCDs, and Stellar Population Analysis for the LMC

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  1. The GRAMS Evolved Star Mass-Loss Models: CMDs, CCDs, and Stellar Population Analysis for the LMC Benjamin Sargent Collaborators: S. Srinivasan, M. Meixner, SAGE, and SAGE-Spec teams Mass-Loss Return from Stars to Galaxies Workshop May 20, 2010

  2. SAGE: Surveying the Agents of a Galaxy’s Evolution • Above left, IRAC and MIPS surveys of 7°x7º area of LMC, Spitzer Legacy program (Meixner et al 2006, AJ, 132, 2268) • Above right, Blum et al (2006, AJ, 132, 2034)

  3. Finding Dust Properties • SEDs: U, B, V, I from MCPS (Zaritsky et al 1997); J, H, Ks from 2MASS (Skrutskie et al 2006), IRAC and MIPS-24 from SAGE • Above, SED of oxygen-rich (O-rich) AGB star; 2Dust (Ueta & Meixner 2003) model of O-rich AGB (Sargent et al 2010) • Below, SED of carbon-rich (C-rich) AGB star; 2Dust model from Srinivasan et al (2010, submitted to A&A)

  4. GRAMS: Grid of Red supergiant and AGB ModelS • spherical symmetry, Rmax/Rmin=1000, Kim et al (1994) size distribution: n(a) = C*a-3.5exp[-a/a0] • O-rich dust: O-deficient silicates (Ossenkopf et al 1992), a0=0.01m, amin=0.1m • O-rich models: Teff = 2100-4700K, log10(L)=3-6, 10=0.0001-32, Rmin=3, 7, 11, 15 • C-rich dust: 90% amorph. carbon (Zubko et al. 1996), 10% SiC (Pégourié 1988), a0=0.1m, amin=1m. 88/12 C/SiC for previous model • C-rich models: Teff = 2600-3500K, log10(L)=3-5.5, 11.3=0.001-1, Rmin=1.5, 4.5, 7, 12

  5. CMDs: O-rich model grid • Color-magnitude diagram (CMD) • Good coverage for SAGE and SAGE-Spec O-rich stars • Grid misses for bluest O-AGBs, large errors for faintest sources

  6. CMDs: C-rich model grid • Same CMD, but with C-rich grid and C-AGBs

  7. Color-color diagram: O-rich grid • Right, from Sargent et al (2010b, in prep) • O-AGBs, RSGs, and extreme AGBs identified by Woods et al (2010, in prep) as O-rich in SAGE-Spec (Kemper et al 2010, submitted) well-fit by models, but confusion with C-rich AGBs at K-[3.6] > 1.5

  8. Color-color diagram: C-rich grid • Above, from Srinivasan et al (2010, in prep) • Better coverage of extreme AGBs than O-rich

  9. SED-fitting • Currently using 2 minimization routine in IDL (S. Srinivasan) • Eventually adapt Robitaille et al. (2006) YSO SED-fitter to GRAMS model grid • O-rich AGBs and RSGs typically fit well by O-rich grid

  10. SED-fitting & Dust Chemistry • Right: An SED for an extreme AGB star candidate • Best-fit models from both O-rich and C-rich grids shown on figure • C-rich model (in green) provides much better fit, especially for IRAC bands

  11. Stellar Masses and Ages • Right: Marigo et al. (2008) isochrones for Z=0.008 (LMC) • O-rich AGBs and RSGs (Teff, L) from SED-fitting overplotted • Points under 104 LSun & Teff < 103.5 K due to variability (A. Lançon, priv. communication)?

  12. O-rich Grid & Stellar Masses • Above right: histogram of stellar mass from fitting to Marigo et al (2008) Z=0.008 isochrones • Below right: [24] vs. [8.0]-[24] CMD • O-rich AGB stars with M > 2.7 MSun typically on “bright” branch of O-rich AGBs

  13. Stellar Populations applications? • MLR, Teff, L come from SED-fitting • Mass and age from Marigo et al 2008 isochrones

  14. O-, C-, & extreme AGB Mass-Loss • Right, Srinivasan et al (2009, AJ, 137, 4810) • 0.14, 0.24, & 2.4 x 10-5 MSun/yr total, from O-, C-, & extreme AGBs, respectively • From SED-fitting, 0.64, 0.14, & 2.3 x 10-5 MSun/yr total, respectively (about 18000 O-AGBs, 7000 C-AGBs, & 1400 extremes) • 0.048 x 10-5 MSun/yr from ~110 RSGs

  15. Conclusions • Spitzer CMDs and CCDs better separate O- and C-rich evolved stars than previous surveys allowed, but SED-fitting is quite powerful in this regard. • Applications to stellar populations studies. • Extreme AGBs produce most dust, but how many C-rich versus O-rich? Probably most have carbon dust. But, per star, RSGs really pull their weight in returning mass … • AGB/RSG contribution to LMC mass budget comparable to SNe contribution? Masaaki Otsuka will discuss SNe contribution tomorrow morning. • Stay tuned for further SAGE work on SMC (Karl Gordon, Martha Boyer, et al) and LMC (Sundar Srinivasan, myself, et al)

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