The GRAMS Evolved Star Mass-Loss Models: CMDs,

CCDs, and Stellar Population Analysis for the LMC

Benjamin SargentCollaborators: S. Srinivasan, M. Meixner,

SAGE, and SAGE-Spec teams

Mass-Loss Return from Stars to Galaxies Workshop

May 20, 2010

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)

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)

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=0.01m, amin=0.1m

• 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=0.1m, amin=1m. 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

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

CMDs: C-rich model grid

• Same CMD, but with C-rich grid and C-AGBs

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

Color-color diagram: C-rich grid

• Above, from Srinivasan et al (2010, in prep)• Better coverage of extreme AGBs than O-rich

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

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

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)?

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

Stellar Populations applications?

• MLR, Teff, L come from SED-fitting

• Mass and age from Marigo et al 2008 isochrones

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

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)