et al. 1996; Hansen 2005; Kalirai et al ML is a free parameter with a huge astrophysical impact

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2 Rood 1973; Fusi Pecci & Renzini 1975,1976; Renzini 1977; Castellani & Tornambe 1981; Peterson 1982; Castellani & Castellani 1993; Fusi Pecci et al. 1993; D Cruz et al. 1996; Hansen 2005; Kalirai et al ML is a free parameter with a huge astrophysical impact stellar evolution modeling UV excess in elliptical galaxies interaction between the cool intracluster medium & hot halo gas little theoretical or observational guidance on how to incorporate ML into models Reimers 1975: dm/dt = η4x10-13 L/gR [M o /yr] η = 0.3 for RGB ML

3 Judge & Stencel 1991, ApJ 371, 357

4 fundamental issues... best observational targets Galactic GCs best diagnostics rates duty cycles total mass lost - dependence on metallicity - impact on HB morphology - driving mechanism(s)

5 ML diagnostics in RGB stars T~4000 K, L ~10 2 L o, R ~20 R o v exp ~10 km/s CS dusty envelopes outflow in the chromosphere o K 10 2 R 10 6 a few R yr

6 profile asymmetry & coreshifts lines: Ha, NaI D, CaII K, Mg II λ2800 h,k, HeI λ can trace an active chromosphere and/or mass outflow Gratton 83; Cacciari & Freeman 83; Gratton etal 84; Dupree etal 84; Dupree etal 92, 94; Lyons etal 96; Smith etal 04; Cacciari etal 04; Mauas etal 06 effective to trace the region of wind formation & acceleration difficult to convert wind line diagnostics into ML rates (both modeling & sampled region issues) very high s/n & spectral resolution the current generation of 4-8m telescopes can measure only the brightest GCs giants

7 ML diagnostics in RGB stars IR dust emission linear polarization microwave CO emission radio OH maser emission CS dusty envelopes CS envelopes of Pop II giants have intrinsically low surface brightness far IR & radio receivers have not enough spatial res & sensitivity to study Pop II CSE in dense stellar fields polarization (<<1%) hardly measurable 3-20 micron spectro spectro-photometryphotometry most effective to detect Pop II CSE o K 10 2 R yr

8 piooneering works: Frogel & Elias 1988: K,L,M,N photometry of red variables in GGCs Gillet et al. 1988: IRAS obs of 47 Tuc ISO era Hopwood et al. 1999; Evans et al. 2003: far IR ISOPHOT obs of GGCs only upper limits! Randani & Jorissen 2001: ISOCAM obs of bright AGB stars in 47 Tuc dust excess in 2 objects! Origlia et al. 2002: ISOCAM obs of RGB stars in 6 massive GCCs

9 Spitzer era: Boyer etal 2006, AJ 132, 1415: IRAC+MIPS+IRS obs of M M o intra-cluster dust accumulated within 1 Myr 20 dusty AGB & post-agb stars 5-15 µm m spectrum of the PNK648: [Ne[ Ne/H]= /H]=-0.7; [S/H]=-2.7 Lebzelter etal 2006, ApJ 653, 145: IRS spectra of 47Tuc giants amorphous silicates & oxides Boyer etal 2008, AJ 135, 1395: IRAC+MIPS obs of ω Cen <10-4 M o intra-cluster dust accumulated over the last Myr 140 dusty AGB & Tip RGB post-agb van Loon etal 2008, ApJ 680, 52: IRAC obs of NGC6791 lack of enhanced ML

10 our contrubution: survey GO#20298, PI: R.T.Rood, CoIs: Origlia, Ferraro, Fusi Pecci, Rich Exploring the Unknown Physics of Mass Loss in First Ascent Pop II Red giants 26hr - deep imaging (down to the ~HB) of 17 GGCs spanning the entire range of Z & HB morphologies

11 HB morphology metallicity: 1 st parameter [Fe/H]=-1.6 [Fe/H]=-0.7

12 HB morphology same metallicity,, different lenght 2 nd nd parameter(s) NGC 6388 NGC 6441

13 HB morphology a magnifier of mass loss in RGB mass loss

14 techniques: mid IR photometry in the 3.6,4.5,5.8,8 µm IRAC bands: dust emission & physical parameters, ML rate & duty cycle near IR ground based photometry: stellar counterparts, photospheric parameters data reduction: photometric reduction: : PSF fitting in crowded fields (ROMAFOT+DAOPHOT) astrometry: : 2MASS tools: CMDs, LFs,, color excess, star counts

15 47 Tuc Origlia et al ISOCAM 40! detected almost 800 stars!

16 - stars with dust excess >3 - blends removed >3σ from the from the ridge line NGC6388 NGC 2808 M15

17 fundamental issues... best observational targets Galactic GCs most effective diagnostics mid IR phot of CSE rates duty cycles total mass lost dependence on metallicity impact on HB morphology driving mechanism(s)

18 assumptions: ad hoc version of the DUSTY code (Ivezic to include diagnostics in the IRAC bands Ivezic, Nenkova &Elitzur 1999) radiative transport equation in an expanding dusty envelope under the general assumption of v exp = constant density 1/r 2 constant, density dust driven wind assumption does not work (see also Wilson 2000): low mass giants are neither luminous nor metal rich enough for this t mechanism to be efficient measured quantities: T eff, color excess, flux output from DUSTY: τ (IRAC), F (IRAC), r env

19 rates: dm/dt = 4 π r ρ env2 dust δ v exp ρ dust ρ grain τ F obs /F mod D 2 δ=ρ gas /ρ dust 1/Z in GCs means that ~50% of α-elements can condense in dust v exp δ -0.5 if dust & gas coupled (e.g Morris et al. 96) in 47 Tuc: δ=200 vexp =10 km/s

20 dm/dt ~ Z - 0.3

21 Reimers

22 fundamental issues... best observational targets Galactic GCs most effective diagnostics mid IR phot of CSE rates ~Z -1/3 duty cycles total mass lost - dependence on metallicity - impact on HB morphology - driving mechanism(s)

23 CSEs dusty CSEs detected in a fraction of RGBs, only! f=(n d /N) after correction for - incompleteness - field contamination - AGB stars - blending M15 NGC2808 NGC6388

24 f ~ Z +0.4 frequency

25 dusty CSEs detected in a fraction of RGBs, only! intrinsic to the stochastic dust formation process? - ad hoc (low?) efficiencies with varying L * & [M/H]... - not dusty driven winds... episodic mass loss process? very likely, although modulation mechanism still unknown oscillation, magnetic activity, rotation, deep mixing... one more important constraint!

26 M RGB M RGB too high! = Σ i (dm/dt) i x dt i evolutionary timescale episodic mass loss... M RGB = Σ i (dm/dt) i x dt i x f i duty cycle

27 fundamental issues... best observational targets Galactic GCs most effective diagnostics mid IR phot of CSE rates ~Z -0.3 duty cycles ~Z +0.4 total mass lost - dependence on metallicity - impact on HB morphology - driving mechanism(s)

28 M RGB = Σ i (dm/dt) i x dt i x f i

29 M M ~ Z

30 M15 NGC6388

31 conclusions... best observational targets Galactic GCs most effective diagnostics mid IR phot of CSE rates ~Z -0.3 duty cycles total mass lost - dependence on metallicity mild - impact on HB morphology yes! - driving mechanism(s)? radiation pressure no!