A<i>SPITZER SPACE TELESCOPE</i>ATLAS OF ω CENTAURI: THE STELLAR POPULATION, MASS LOSS, AND THE INTRACLUSTER MEDIUM

Boyer, Martha L.; McDonald, Iain; Loon, Jacco Th. van; Woodward, C. E.; Gehrz, R. D.; Evans, A.; Dupree, A. K.

doi:10.1088/0004-6256/135/4/1395

Cited by 55 publications

(66 citation statements)

References 77 publications

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“…(Lagadec et al 2007;Matsuura et al 2007;Sloan et al 2009Sloan et al , 2012Whitelock et al 2009;Menzies et al 2010Menzies et al , 2011McDonald et al 2014) and in globular clusters with > -[ ] Fe H 1.6 (Boyer et al 2008(Boyer et al , 2009McDonald et al 2009McDonald et al , 2011. All of these examples are C stars or low-mass M-type stars.…”

Section: Introductionmentioning

confidence: 99%

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs^*

Boyer¹,

McQuinn

Groenewegen

et al. 2017

ApJ

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The survey for DUST in Nearby Galaxies with Spitzer (DUSTiNGS) identified several candidate Asymptotic Giant Branch (AGB) stars in nearby dwarf galaxies and showed that dust can form even in very metal-poor systems (~ Z Z 0.008 ). Here, we present a follow-up survey with WFC3/IR on the Hubble Space Telescope (HST), using filters that are capable of distinguishing carbon-rich (C-type) stars from oxygen-rich (M-type) stars: F127M, F139M, and F153M. We include six star-forming DUSTiNGS galaxies (NGC 147, IC 10, Pegasus dIrr, Sextans B, Sextans A, and Sag DIG), all more metal-poor than the Magellanic Clouds and spanning 1dex in metallicity. We double the number of dusty AGB stars known in these galaxies and find that most are carbon rich. We also find 26 dusty M-type stars, mostly in IC 10. Given the large dust excess and tight spatial distribution of these M-type stars, they are most likely on the upper end of the AGB mass range (stars undergoing Hot Bottom Burning). Theoretical models do not predict significant dust production in metal-poor M-type stars, but we see evidence for dust excess around M-type stars even in the most metal-poor galaxies in our sample ( + = ( ) -12 log O H 7.26 7.50). The low metallicities and inferred high stellar masses (up to ∼10  M ) suggest that AGB stars can produce dust very early in the evolution of galaxies (∼30 Myr after they form), and may contribute significantly to the dust reservoirs seen in high-redshift galaxies.

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Section: Introductionmentioning

confidence: 99%

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs^*

Boyer¹,

McQuinn

Groenewegen

et al. 2017

ApJ

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“…Indeed, the IRAC bands between 3.6 and 8 μm are effective in detecting warm dust with spatial resolution good enough to resolve a large fraction of the GC giants. By using the (3.6−8) Spitzer-IRAC color as a diagnostic, dust excess has been detected around some of the brightest giants in ω Cen, M 15, NGC 362 and 47 Tuc (Boyer et al 2006(Boyer et al , 2008(Boyer et al , 2009(Boyer et al , 2010.…”

Section: Introductionmentioning

confidence: 99%

An empirical mass-loss law for Population II giants from theSpitzer-IRAC survey of Galactic globular clusters

Origlia

Ferraro

Fabbri

et al. 2014

A&A

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Aims. The main aim of the present work is to derive an empirical mass-loss (ML) law for Population II stars in first and second ascent red giant branches. Methods. We used the Spitzer InfraRed Array Camera (IRAC) photometry obtained in the 3.6-8 μm range of a carefully chosen sample of 15 Galactic globular clusters spanning the entire metallicity range and sampling the vast zoology of horizontal branch (HB) morphologies. We complemented the IRAC photometry with near-infrared data to build suitable color-magnitude and color-color diagrams and identify mass-losing giant stars. Results. We find that while the majority of stars show colors typical of cool giants, some stars show an excess of mid-infrared light that is larger than expected from their photospheric emission and that is plausibly due to dust formation in mass flowing from them. For these stars, we estimate dust and total (gas + dust) ML rates and timescales. We finally calibrate an empirical ML law for Population II red and asymptotic giant branch stars with varying metallicity. We find that at a given red giant branch luminosity only a fraction of the stars are losing mass. From this, we conclude that ML is episodic and is active only a fraction of the time, which we define as the duty cycle. The fraction of mass-losing stars increases by increasing the stellar luminosity and metallicity. The ML rate, as estimated from reasonable assumptions for the gas-to-dust ratio and expansion velocity, depends on metallicity and slowly increases with decreasing metallicity. In contrast, the duty cycle increases with increasing metallicity, with the net result that total ML increases moderately with increasing metallicity, about 0.1 M every dex in [Fe/H]. For Population II asymptotic giant branch stars, we estimate a total ML of ≤0.1 M , nearly constant with varying metallicity.

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“…Results from mid-infrared observations of metal-deficient field giants and globular clusters with IRAS, the ISO satellite, the Spitzer Space Telescope, and AKARI (Smith 1998;Origlia et al 2002Origlia et al , 2007Evans et al 2003;Boyer et al 2006;Ita et al 2007;Boyer et al 2008) suggest that some giants have produced circumstellar dust that could result from stellar winds. Since not all giants display excess infrared emission, mass loss associated with dust appears to be episodic (Origlia et al 2007;Mészáros et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Fast Winds and Mass Loss From Metal-Poor Field Giants

Dupree

Smith

Strader

2009

The Astronomical Journal

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Echelle spectra of the infrared He i λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He i line is ubiquitous in stars with T eff 4500 K and M V fainter than −1.5, and reveals the dynamics of the atmosphere. The line strength increases with effective temperature for T eff 5300 K in RHB stars. In AGB and RGB stars, the line strength increases with luminosity. Fast outflows ( 60 km s −1 ) are detected from the majority of the stars and about 40% of the outflows have sufficient speed as to allow escape of material from the star as well as from a globular cluster. Outflow speeds and line strengths do not depend on metallicity for our sample ([Fe/H]= −0.7 to −3.0), suggesting the driving mechanism for these winds derives from magnetic and/or hydrodynamic processes. Gas outflows are present in every luminous giant, but are not detected in all stars of lower luminosity indicating possible variability. Mass loss rates ranging from ∼3 × 10 −10 to ∼6 × 10 −8 M yr −1 estimated from the Sobolev approximation for line formation represent values with evolutionary significance for red giants and RHB stars. We estimate that 0.2 M will be lost on the RGB, and the torque of this wind can account for observations of slowly rotating RHB stars in the field. About 0.1-0.2 M will be lost on the RHB itself. This first empirical determination of mass loss on the RHB may contribute to the appearance of extended horizontal branches in globular clusters. The spectra appear to resolve the problem of missing intracluster material in globular clusters. Opportunities exist for "wind smothering" of dwarf stars by winds from the evolved population, possibly leading to surface pollution in regions of high stellar density.

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ASPITZER SPACE TELESCOPEATLAS OF ω CENTAURI: THE STELLAR POPULATION, MASS LOSS, AND THE INTRACLUSTER MEDIUM

Cited by 55 publications

References 77 publications

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs^*

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs^*

An empirical mass-loss law for Population II giants from theSpitzer-IRAC survey of Galactic globular clusters

Fast Winds and Mass Loss From Metal-Poor Field Giants

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ASPITZER SPACE TELESCOPEATLAS OF ω CENTAURI: THE STELLAR POPULATION, MASS LOSS, AND THE INTRACLUSTER MEDIUM

Cited by 55 publications

References 77 publications

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs*

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs*

An empirical mass-loss law for Population II giants from theSpitzer-IRAC survey of Galactic globular clusters

Fast Winds and Mass Loss From Metal-Poor Field Giants

Contact Info

Product

Resources

About

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs^*

An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-redshift AGB Analogs^*