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

Pepe, Carolina; Pellizza, L. J.

doi:10.1093/mnras/stw1095

Cited by 4 publications

(5 citation statements)

References 52 publications

(56 reference statements)

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“…It has also been suggested that, in the presence of an IMBH in the centre of the cluster, the gas density profile should be constantly decreasing (Pepe & Pellizza 2016). We first tested a model in which the gas density drops as 1/r:…”

Section: Decreasing Modelmentioning

confidence: 99%

“…A more detailed modelling of the gas density could in principle be used as a tracer of the origin and evolution of the gas itself. Furthermore, it has been suggested that the distribution of gas could be influenced by the presence of an intermediate mass black hole (Pepe & Pellizza 2016), thus allowing us to put additional constraints on its presence. Stringent upper limits have been put in the past on the mass of the central IMBH in 47 Tuc between 1000 -5000 M from both kinematic methods and radio continuum observations (McLaughlin et al 2006;Maccarone & Servillat 2008, 2010Lu & Kong 2011).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Internal gas models and central black hole in 47 Tucanae using millisecond pulsars

Abbate

Possenti

Ridolfi

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Despite considerations of mass loss from stellar evolution suggesting otherwise, the content of gas in globular clusters seems poor and hence its measurement very elusive. One way of constraining the presence of ionized gas in a globular cluster is through its dispersive effects on the radiation of the millisecond pulsars included in the cluster. This effect led Freire et al. in 2001 to the first detection of any kind of gas in a globular cluster in the case of 47 Tucanae. By exploiting the results of 12 additional years of timing, as well as the observation of new millisecond pulsars in 47 Tucanae, we revisited this measurement: we first used the entire set of available timing parameters in order to measure the dynamical properties of the cluster and the three-dimensional position of the pulsars. Then we applied and tested various gas distribution models: assuming a constant gas density, we confirmed the detection of ionized gas with a number density of n = 0.23 ± 0.05 cm −3 , larger than the previous determination (at 2σ uncertainty). Models predicting a decreasing density or following the stellar distribution density are highly disfavoured. We are also able to investigate the presence of an intermediate mass black hole in the centre of the cluster, showing that is not required by the available data, with an upper limit for the mass at ∼ 4000 M .

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Section: Decreasing Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Internal gas models and central black hole in 47 Tucanae using millisecond pulsars

Abbate

Possenti

Ridolfi

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Lacking a smoking-gun, uncontroversial direct IMBH detection, indirect detection methods based on IMBH dynamical effects in GCs are useful for compiling a list of candidate hosts for follow up. The observable effects (see Mezcua 2017 for a recent and quite comprehensive review of IMBH detection attempts) include the presence of a central cusp in surface density (Bahcall & Wolf 1976;Newell et al 1976) and/or velocity dispersion (Peterson et al 1989;Noyola et al 2006Noyola et al , 2008Lützgendorf et al 2011Lützgendorf et al , 2012Lützgendorf et al , 2013bLützgendorf et al , 2016Lützgendorf et al , 2017Feldmeier et al 2013;Lanzoni et al 2013;Lanzoni 2016;Lanzoni & Cosmic-Lab Team 2016;Askar et al 2017a), masssegregation reduction (Baumgardt et al 2004;Gill et al 2008;Pasquato et al 2009Pasquato et al , 2016Beccari et al 2010;Umbreit & Rasio 2013;Di Cintio et al 2023), anomalous accelerations from pulsar timing (Peuten et al 2014;Kızıltan et al 2017;Perera et al 2017;Gieles et al 2018), high-velocity stars (Meylan et al 1991;Lützgendorf et al 2011;Fragione & Gualandris 2019), and other clues (Miocchi 2007;Pasquato & Bertin 2008Leigh et al 2014;Pepe & Pellizza 2016;Askar et al 2017a).…”

Section: Introductionmentioning

confidence: 99%

Interpretable Machine Learning for Finding Intermediate-mass Black Holes

Pasquato,

Trevisan,

Askar

et al. 2024

ApJ

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Definitive evidence that globular clusters (GCs) host intermediate-mass black holes (IMBHs) is elusive. Machine-learning (ML) models trained on GC simulations can in principle predict IMBH host candidates based on observable features. This approach has two limitations: first, an accurate ML model is expected to be a black box due to complexity; second, despite our efforts to simulate GCs realistically, the simulation physics or initial conditions may fail to reflect reality fully. Therefore our training data may be biased, leading to a failure in generalization to observational data. Both the first issue—explainability/interpretability—and the second—out of distribution generalization and fairness—are active areas of research in ML. Here we employ techniques from these fields to address them: we use the anchors method to explain an Extreme Gradient Boosting (XGBoost) classifier; we also independently train a natively interpretable model using Certifiably Optimal RulE ListS (CORELS). The resulting model has a clear physical meaning, but loses some performance with respect to XGBoost. We evaluate potential candidates in real data based not only on classifier predictions but also on their similarity to the training data, measured by the likelihood of a kernel density estimation model. This measures the realism of our simulated data and mitigates the risk that our models may produce biased predictions by working in extrapolation. We apply our classifiers to real GCs, obtaining a predicted classification, a measure of the confidence of the prediction, an out-of-distribution flag, a local rule explaining the prediction of XGBoost, and a global rule from CORELS.

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“…Still, observations indicate about 0.1 M ⊙ of ionized gas in the central few parsecs of 47 Tuc and M15 (Pfahl & Rappaport 2001;Freire et al 2001) and (tentatively) about 0.3 M ⊙ of neutral gas in M15 (van Loon et al 2006). Numerical studies of gas removal between disk crossings suggest a diversity of gas properties among Galactic GCs (Priestley et al 2011;Pepe & Pellizza 2013;McDonald & Zijlstra 2015;Pepe & Pellizza 2016).…”

mentioning

confidence: 99%