Gas in globular clusters. II - Time-dependent flow models

VandenBerg, Don A.; Faulkner, D. J.

doi:10.1086/155695

Cited by 19 publications

(36 citation statements)

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“…The other second-parameter cluster in the same set (see Section 5.3.2) is M12. It is located just below M56 and NGC 6934 in Figure 39, and since its mass is within the ∼0.1-0.15 dex uncertainty associated with the dashed line (see VandenBerg & Faulkner 1977), it may or may not be able to develop a steady-state outflow. Of the GCs that are represented by open circles, the ones that seem to have the most anomalous locations on the mass-v e,0 plane are M3 and M53.…”

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 96%

“…For our cluster sample, the apparent overlap of clusters represented by both open and filled circles at a value of log M/M just above 5.1 (the location of the horizontal, dashed line) appears to mark the mean transition mass between lower mass GCs that develop steady-state winds and higher mass systems that could acquire growing gas reservoirs at their centers as a result of gas inflows. (This transition mass is predicted to vary inversely with the value of the concentration parameter, c; see VandenBerg & Faulkner 1977) In support of this possibility, we note that NGC 6752 and M30 are collapsed-core GCs with c = 2.50 (according to the 2010 edition of the catalog compiled by Harris 1996); consequently, it would not be too surprising that they might be able to retain the gas from low-velocity winds when other clusters of similar mass but lower central concentrations (such as NGC 6584 and NGC 6934, which both have c ≈ −1.5) develop steady-state outflows. NGC 6397 and M70 are also collapsedcore, c = 2.50 GCs, and their present masses, which are less than those of NGC 6752 and M30, appear to be low enough ( 10 5 M ) that winds should be able to dissipate the gas which is produced by normal stellar mass-loss processes.…”

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 99%

“…In Figure 39, the masses of several GCs of interest are plotted as a function of their central escape velocities, v e,0 . The masses were derived from the M V values listed in Table 2 assuming a mass-to-light ratio M/L V = 1.6(M/L V ) (Illingworth 1976;Pryor et al 1991;Albrow et al 2002), whereas v e,0 was calculated using the method described by VandenBerg & Faulkner (1977;see their Section V). (Masses derived in this way are probably uncertain by at least ∼ ± 25%: more massive, centrally concentrated clusters appear to have average mass-tolight ratios closer to 2; see, e.g., the study of M15 by Pasquali et al 2004.)…”

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 99%

“…(Values of log σ 0 for all of the GCs in our sample are listed in Table 2: these have been calculated using the relations described by VandenBerg & Faulkner 1977. ) If the value of α is taken to be 4×10 −19 s −1 , as adopted by Faulkner & Freeman (1977), ram-pressure sweeping by a halo medium with a density of 10 −26 g cm −3 would be effective in clusters that have log σ 0 v e,0 5.7.…”

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 99%

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THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED $\Delta V^{\rm HB}_{\rm TO}$ METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

VandenBerg

Brogaard

Leaman

et al. 2013

ApJ

450

407

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Ages have been derived for 55 globular clusters (GCs) for which Hubble Space Telescope Advanced Camera for Surveys photometry is publicly available. For most of them, the assumed distances are based on fits of theoretical zero-age horizontal-branch (ZAHB) loci to the lower bound of the observed distributions of HB stars, assuming reddenings from empirical dust maps and metallicities from the latest spectroscopic analyses. The age of the isochrone that provides the best fit to the stars in the vicinity of the turnoff (TO) is taken to be the best estimate of the cluster age. The morphology of isochrones between the TO and the beginning part of the subgiant branch (SGB) is shown to be nearly independent of age and chemical abundances. For well-defined color-magnitude diagrams (CMDs), the error bar arising just from the "fitting" of ZAHBs and isochrones is ≈ ± 0.25 Gyr, while that associated with distance and chemical abundance uncertainties is ∼±1.5-2 Gyr. The oldest GCs in our sample are predicted to have ages of ≈13.0 Gyr (subject to the aforementioned uncertainties). However, the main focus of this investigation is on relative GC ages. In conflict with recent findings based on the relative main-sequence fitting method, which have been studied in some detail and reconciled with our results, ages are found to vary from mean values of ≈12.5 Gyr at [Fe/H] −1.7 to ≈11 Gyr at [Fe/H] −1. At intermediate metallicities, the age-metallicity relation (AMR) appears to be bifurcated: one branch apparently contains clusters with disk-like kinematics, whereas the other branch, which is displaced to lower [Fe/H] values by ≈0.6 dex at a fixed age, is populated by clusters with halo-type orbits. The dispersion in age about each component of the AMR is ∼±0.5 Gyr. There is no apparent dependence of age on Galactocentric distance (R G ) nor is there a clear correlation of HB type with age. As previously discovered in the case of M3 and M13, subtle variations have been found in the slope of the SGB in the CMDs of other metal-poor ([Fe/H] −1.5) GCs. They have been tentatively attributed to clusterto-cluster differences in the abundance of helium. Curiously, GCs that have relatively steep "M13-like" SGBs tend to be massive systems, located at small R G , that show the strongest evidence of in situ formation of multiple stellar populations. The clusters in the other group are typically low-mass systems (with 2-3 exceptions, including M3) that, at the present time, should not be able to retain the matter lost by mass-losing stars due either to the development of GC winds or to ram-pressure stripping by the halo interstellar medium. The apparent separation of the two groups in terms of their present-day gas retention properties is difficult to understand if all GCs were initially ∼20 times their current masses. The lowest-mass systems, in particular, may have never been massive enough to retain enough gas to produce a significant population of second-generation stars. In this case, the observed light element abundance variations, ...

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Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 96%

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 99%

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 99%

Section: On the Retention Of Mass-loss Materials By Globular Clustersmentioning

confidence: 99%

See 2 more Smart Citations

THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED $\Delta V^{\rm HB}_{\rm TO}$ METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

VandenBerg

Brogaard

Leaman

et al. 2013

ApJ

450

407

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“…The central escape speed v e from a globular cluster is given by the equation (King 1966;VandenBerg and Faulkner 1977) v 2. e GMJSttW 0 r eff \ 9/1* 10 c/2 +2X 10…”

Section: The Retention Of Primordial Nova Ejecta Within Globular Clusmentioning

confidence: 99%

On the Possibility of Nova Enrichment of Globular Clusters

Smith¹,

Kraft²

1996

PASP

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ABSTRACT. Primordial chemical enrichment of globular clusters by Ne novae could provide a means for producing significant enhancements in 13 C, 25 Mg, and 27 A1 abundances among cluster stars, if such novae eject on the order of 10" 4 M 0 of processed material. Enrichment by Ne novae may lead to cluster giants which have relatively large surface [Al/Fe] abundance ratios, either through direct enhancement of the 27 A1 surface abundances of the main-sequence progenitors of these stars, or through primordial enhancements in 25 Mg, which can be converted to 27 A1 by proton-addition nucleosynthesis in the O^N burning shell of red giants.

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6.2.1 Globular clusters

Seggewiss¹

Stars and Star Clusters

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Gas in globular clusters. II - Time-dependent flow models

Cited by 19 publications

References 0 publications

THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED $\Delta V^{\rm HB}_{\rm TO}$ METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED $\Delta V^{\rm HB}_{\rm TO}$ METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

On the Possibility of Nova Enrichment of Globular Clusters

6.2.1 Globular clusters

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