The observability of ionized interstellar gas in globular clusters

Scott, E. H.; Rose, William K.

doi:10.1086/153496

Cited by 25 publications

(27 citation statements)

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“…Recent studies on their stellar populations find similar ages for NGC 6388 as 47 Tuc (Moretti et al 2009), therefore we set n = 0.1 cm −3 for NGC 6388. However, a higher gas content may be expected for NGC 6388 (Scott & Rose 1975). We also set v = 0 km s −1 and c s = 15 km s −1 .…”

Section: Bondi-hoyle Accretion and Comparison With G1mentioning

confidence: 99%

Radio observations of NGC 6388: an upper limit on the mass of its central black hole

Cseh¹,

Kaaret²,

Corbel³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We present the results of deep radio observations with the Australia Telescope Compact Array (ATCA) of the globular cluster NGC 6388. We show that there is no radio source detected (with an rms noise level of 27 μJy) at the cluster centre of gravity or at the locations of any of the Chandra X‐ray sources in the cluster. Based on the fundamental plane of accreting black holes which is a relationship between X‐ray luminosity, radio luminosity and black hole mass, we place an upper limit of ∼1500 M on the mass of the putative intermediate‐mass black hole located at the centre of NGC 6388. We discuss the uncertainties of this upper limit and the previously suggested black hole mass of based on surface density profile analysis.

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Section: Bondi-hoyle Accretion and Comparison With G1mentioning

confidence: 99%

Radio observations of NGC 6388: an upper limit on the mass of its central black hole

Cseh¹,

Kaaret²,

Corbel³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…There is strong observational and theoretical evidence that stars reaching the AGB phase lose a large amount of mass. Several studies have been devoted to the fate of this gas in clusters (Scott & Rose 1975;Faulkner & Freeman 1977;Vandenberg & Faulkner 1977;Vandenberg 1978;Scott & Durisen 1978;Faulkner 1984;Faulkner & Coleman 1984;Smith 1996). Stellar ejecta in GCs with shallow potential wells can leave the cluster via a smooth wind-like outflow.…”

Section: Introductionmentioning

confidence: 99%

Accretion of gas by globular cluster stars

Thoul

Jorissen

Goriely

et al. 2002

A&A

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Abstract. Some recent observations of the abundances of s-process, r-process, and α elements in metal-poor stars have led to a new scenario for their formation. According to this scenario, these stars were born in a globular cluster and accreted the s-process enriched gas expelled by cluster stars of higher-mass, thereby modifying their surface abundances. Later on, these polluted stars evaporated from the globular cluster to constitute an important fraction of the current halo population. In addition, there are now many direct observations of abundance anomalies not only in globular cluster giant stars but also in subgiant and main-sequence stars. Accretion again provides a plausible explanation for (at least some of) these peculiarities. Here we investigate further the efficiency of the accretion scenario. We find that in concentrated clusters with large escape velocities, accretion is very efficient and can indeed lead to major modifications of the stellar surface abundances.

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“…Clearly, the detection of the ISM and the determination of its temperature would be crucial to confirm the existence of an IMBH in these GCs and, therefore, to support the hypothesis of accretion as an efficient cleansing mechanism. However, as pointed out by different authors (e.g., Scott & Rose 1975, and references therein), the gas temperature should depend only on the properties of the radiation field of the cluster. The ISM of GCs with an important source of UV radiation is expected to be ionized at T ≳ 10 4 K. From the GCs listed above, only four (47 Tuc, NGC 2808, M 15 and M 62) have stars hot enough to provide a wealth of UV radiation (log T > 4.3) (O'Connell et al 1997;Miocchi 2007) 6 .…”

Section: Discussionmentioning

confidence: 96%

“…In both cases the authors assume that the most evolved stars contribute to the ISM by means of their winds. However, Scott & Rose (1975) assume that there is sufficient stellar ultraviolet radiation to maintain hydrogen fully ionized and that this is the unique energy input to the gas system while Faulkner & Freeman (1977) consider the corresponding injection of energy and the consequent collisional ionization by electrons along with the associated radiative cooling of the gas. Under the same physical assumptions, the work of Faulkner & Freeman (1977) was later refined by VandenBerg & Faulkner (1977), who investigated the time-dependent equations.…”

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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The observability of ionized interstellar gas in globular clusters

Cited by 25 publications

References 0 publications

Radio observations of NGC 6388: an upper limit on the mass of its central black hole

Radio observations of NGC 6388: an upper limit on the mass of its central black hole

Accretion of gas by globular cluster stars

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

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