Gas in globular clusters. I - Time-independent flow models

Faulkner, D. J.; Freeman, K. C.

doi:10.1086/154905

Cited by 26 publications

(41 citation statements)

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“…We will return to this point after describing the gas retention properties of the clusters at the present time.) According to the gas-flow models computed by Faulkner & Freeman (1977) under the most conservative of assumptions (i.e., highly centrally concentrated structures, the neglect of photoionization energy input, etc. ), steady-state outflows (i.e., GC winds) will be very effective in removing the mass-loss material from low-mass clusters for all gas ejection energies down to ∼15 km s −1 , which essentially encompasses all plausible mass-loss mechanisms.…”

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

confidence: 99%

“…where α is the proportional rate of mass loss from stars (i.e., the global mass-loss rate divided by the GC mass; see Faulkner & Freeman 1977) and σ 0 is the surface density of stars at the cluster center (in M pc −2 ). (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.…”

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. Since ρ g (halo) is proportional to α, the same constraint may be obtained for lower values of the halo density, which are probably more realistic (e.g., Silk 1974), simply by assuming smaller values of the uncertain parameter α.…”

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: 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 1 more Smart Citation

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

View full text Add to dashboard Cite

show abstract

“…With a temperature of 100 K, the pressure will be 3.2 × 10 −16 dyne cm −2 . Faulkner & Freeman (1977) constructed time-independent gas flow models for tightly bound clusters. These models suggest pressures at the tidal radius ranging from 0.1 to 5.5 × 10 −16 dyne cm −2 .…”

Section: The Fate Of Wind Materialsmentioning

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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“…Models intending to explain the discrepancy between stellar evolution theories and observations have been developed since the middle 1970s. Scott & Rose (1975) and Faulkner & Freeman (1977) studied an intrinsic cleansing mechanism by solving the steady-state flow equations in one dimension. In both cases the authors assume that the most evolved stars contribute to the ISM by means of their winds.…”

Section: Introductionmentioning

confidence: 99%

Synthetic extinction maps around intermediate-mass black holes in Galactic globular clusters

Pepe

Pellizza

2016

Mon. Not. R. Astron. Soc.

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During the last decades, much effort has been devoted to explain the discrepancy between the amount of intracluster medium (ICM) estimated from stellar evolution theories and that emerging from observations in globular clusters (GCs). One possible scenario is the accretion of this medium by an intermediate-mass black hole (IMBH) at the centre of the cluster. In this work, we aim at modelling the cluster colour-excess profile as a tracer of the ICM density, both with and without an IMBH. Comparing the profiles with observations allows us to test the existence of IMBHs and their possible role in the cleansing of the ICM. We derive the intracluster density profiles from hydrodynamical models of accretion onto a central IMBH in a GC and we determine the corresponding dust density. This model is applied to a list of 25 Galactic GCs. We find that central IMBHs decrease the ICM by several orders of magnitude. In a subset of 9 clusters, the absence of the black hole combined with a low intracluster medium temperature would be at odds with present gas mass content estimations. As a result, we conclude that IMBHs are an effective cleansing mechanism of the ICM of GCs. We construct synthetic extinction maps for M 62 and ω Cen, two clusters in the small subset of 9 with observed 2D extinction maps. We find that under reasonable assumptions regarding the model parameters, if the gas temperature in M 62 is close to 8000 K, an IMBH needs to be invoked. Further ICM observations regarding both the gas and dust in GCs could help to settle this issue.

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Gas in globular clusters. I - Time-independent flow models

Cited by 26 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

Fast Winds and Mass Loss From Metal-Poor Field Giants

Synthetic extinction maps around intermediate-mass black holes in Galactic globular clusters

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