Stellar Populations and Mass Loss in M15: A<i>Spitzer Space Telescope</i>Detection of Dust in the Intracluster Medium

Boyer, Martha L.; Woodward, C. E.; Loon, Jacco Th. van; Gordon, K. D.; Evans, A.; Gehrz, R. D.; Helton, L. A.; Polomski, Elisha

doi:10.1086/506518

Cited by 52 publications

(128 citation statements)

References 60 publications

(88 reference statements)

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“…There is a notable lack of detections of intracluster material with the Spitzer Space Telescope. Only two clusters of the many observed with Spitzer have "possible" detections of intracluster material (Boyer et al 2006;Barmby et al 2009). One suggestion for removal of intracluster material is ram-pressure stripping by the galactic halo (Frank & Gisler 1976, Okada et al 2007), but Spitzer observations cannot confirm the expected relation between cluster kinematics and the presence (or upper limit) of dust (Barmby et al 2009).…”

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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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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“…Smith et al (1995) placed an upper limit of 0.4 M for the molecular gas in M15 from CO observations with the 15 m James Clerk Maxwell Telescope Durrell & Harris (1993). Dusty giants identified with the Spitzer Space Telescope (Boyer et al 2006) and observed with Hectochelle are denoted by squares. The redward "hook" seen among the brightest stars in M15 is not intrinsic to the stars but rather results from saturation of the photographic images (Sneden et al 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Absolute magnitudes are obtained by assuming (m − M) V = 15.37 (Harris 1996). on Mauna Kea. Using the Spitzer Space Telescope, Boyer et al (2006) detected a population of dusty red giants near the center of M15. Observations from Spitzer with the Multiband Imaging Photometer for Spitzer (MIPS) also revealed the ICM discovered by Evans et al (2003) near the core of the globular cluster.…”

Section: Introductionmentioning

confidence: 99%

Mass Outflow and Chromospheric Activity of Red Giant Stars in Globular Clusters. I. M15

Mészáros

Dupree

Szentgyorgyi

2008

The Astronomical Journal

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High-resolution spectra of 110 selected red giant stars in the globular cluster M15 (NGC 7078) were obtained with Hectochelle at the MMT telescope in May, 2006 May, and 2006 October. Echelle orders containing Hα and Ca ii H & K are used to identify emission and line asymmetries characterizing motions in the extended atmospheres. Emission in Hα is detected to a luminosity of log(L/L ) = 2.36, in this very metal-deficient cluster, comparable to other studies, suggesting that the appearance of emission wings is independent of stellar metallicity. The faintest stars showing Hα emission appear to lie on the asymptotic giant branch (AGB) in M15. A line-bisector technique for Hα reveals outflowing velocities in all stars brighter than log(L/L ) = 2.5, and this outflow velocity increases with stellar luminosity, indicating the mass outflow increases smoothly with luminosity. Many stars lying low on the AGB show exceptionally high outflow velocities (up to 10-15 km s −1 ) and more velocity variability (up to 6-8 km s −1 ) than red giant branch (RGB) stars of similar apparent magnitude. High velocities in M15 may be related to the low cluster metallicity. Dusty stars identified from Spitzer Space Telescope infrared photometry as AGB stars are confirmed as cluster members by radial velocity measurements, yet their Hα profiles are similar to those of RGB stars without dust. If substantial mass loss creates the circumstellar shell responsible for infrared emission, such mass loss must be episodic.

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“…Other Spitzer-based studies available on 47 Tuc (Boyer et al 2010), ω Cen (Boyer et al 2008;McDonald et al 2009), M 15 (Boyer et al 2006), and NGC 362 ) find that mass loss is confined near the tip of the RGB, and occurs mostly in AGB or variable stars, with the exception of M 15 where a population of dusty red giants has been detected. These conclusions, however, were revised by Origlia et al (2010) in 47 Tuc where the use of a better dust indicator allowed them to detect dust at fainter magnitudes along the RGB.…”

Section: Introductionmentioning

confidence: 91%

“…Eight Galactic GCs were observed and again only upper limits were found, which is well below expectations for dust production from mass loss in cluster RGB and AGB stars (Barmby et al 2009, and references therein). The only exception is NGC 7078 (M 15) which shows high signal-to-noise evidence for an IR excess and hence dusty intracluster medium in the core (Evans et al 2003;Boyer et al 2006), and possibly ω Cen if the four dust clouds that were detected in the field are confirmed to be intracluster material that is in the process of escaping from the cluster (Boyer et al 2008). This implies that either dust production from mass loss is less efficient, or that the mechanisms able to remove the intracluster material are more efficient than commonly believed.…”

Section: Introductionmentioning

confidence: 99%

Modelling chromospheric line profiles as diagnostics of velocity fields inω Centauri red giant stars

Vieytes

Mauas

Cacciari

et al. 2010

A&A

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Context. Mass loss of ∼0.1−0.3 M from Population II red giant stars (RGB) is a requirement of stellar evolution theory in order to account for several observational evidences in globular clusters. Aims. The aim of this study is to detect the presence of outward velocity fields, which are indicative of mass outflow, in six luminous red giant stars of the stellar cluster ω Cen. Methods. We compare synthetic line profiles computed using relevant model chromospheres to observed profiles of the Hα and Ca II K lines. The spectra were taken with UVES (R = 45 000) and the stars were selected so that three of them belong to the metalrich population and three to the metal-poor population, and sample as far down as 1 to 2.5 mag fainter than the respective RGB tips. Results. We do indeed reveal the presence of low-velocity outward motions in four of our six targets, without any apparent correlation with astrophysical parameters.Conclusions. This provides direct evidence that outward velocity fields and mass motions exist in RGB stars as much as 2.5 mag fainter than the tip. On the assumption that the mass outflow may eventually lead to mass loss from the star, we estimate mass-loss rates of some 10 −9 −10 −10 M yr −1 that are compatible with the stellar evolution requirements. These rates seem to be correlated with luminosity rather than metallicity.

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Stellar Populations and Mass Loss in M15: ASpitzer Space TelescopeDetection of Dust in the Intracluster Medium

Cited by 52 publications

References 60 publications

Fast Winds and Mass Loss From Metal-Poor Field Giants

Fast Winds and Mass Loss From Metal-Poor Field Giants

Mass Outflow and Chromospheric Activity of Red Giant Stars in Globular Clusters. I. M15

Modelling chromospheric line profiles as diagnostics of velocity fields inω Centauri red giant stars

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