Dynamical equivalence, the origin of the Galactic field stellar and binary population, and the initial radius–mass relation of embedded clusters

Belloni, Diogo; Kroupa, Pavel; Rocha-Pinto, Helio J.; Giersz, Mirek

doi:10.1093/mnras/stx3034

Cited by 22 publications

(15 citation statements)

References 55 publications

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“…The Kroupa IBP has successfully explained the observational features of young clusters, stellar associations, and even binaries in old GCs (e.g. Kroupa 2011;Marks & Kroupa 2012;Leigh et al 2015;Belloni et al 2017cBelloni et al , 2018a, and references therein), and our results provide an additional support to this IBP.…”

Section: Discussionsupporting

confidence: 80%

MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters – IV. Cataclysmic variables – properties of bright and faint populations

Belloni

Giersz

Sandoval

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We investigate here populations of cataclysmic variables (CVs) in a set of 288 globular cluster (GC) models evolved with the MOCCA code. This is by far the largest sample of GC models ever analysed with respect to CVs. Contrary to what has been argued for a long time, we found that dynamical destruction of primordial CV progenitors is much stronger in GCs than dynamical formation of CVs, and that dynamically formed CVs and CVs formed under no/weak influence of dynamics have similar white dwarf mass distributions. In addition, we found that, on average, the detectable CV population is predominantly composed of CVs formed via typical common envelope phase (CEP) ( 70 per cent), that only ≈ 2-4 per cent of all CVs in a GC is likely to be detectable, and that core-collapsed models tend to have higher fractions of bright CVs than non-core-collapsed ones. We also consistently show, for the first time, that the properties of bright and faint CVs can be understood by means of the pre-CV and CV formation rates, their properties at their formation times and cluster half-mass relaxation times. Finally, we show that models following the initial binary population proposed by Kroupa and set with low CEP efficiency better reproduce the observed amount of CVs and CV candidates in NGC 6397, NGC 6752 and 47 Tuc. To progress with comparisons, the essential next step is to properly characterize the candidates as CVs (e.g. by obtaining orbital periods and mass ratios). such as the Hubble Space Telescope (HST) and the Chandra X-ray Observatory are required to detect them. Until now the best studied GCs with respect to CV populations are NGC 6397 (Cohn et al. 2010), NGC 6752 (Lugger et al. 2017), ω Cen (Cool et al. 2013) and 47 Tuc (Rivera Sandoval et al. 2018). The identification of CVs in these GCs has been carried out by identifying HST optical counterparts to Chandra X-ray sources. Usually these counterparts show an Hα excess (suggesting the presence of an accretion disc), they are bluer than the MS stars and several also show photometric variability in different bands.In the core-collapsed 1 clusters NGC 6397 and NGC 6752, Cohn et al. (2010) and Lugger et al. (2017) found the CVs to be 1 Core collapse is a process in which the GC core evolves by releasing potential energy to the outer parts (via two-body relaxation) and thus becoming hotter and more compact, due to its negative heat capacity. The © 2018 The Authors 2 D. Belloni et al.divided into two populations, a bright and a faint one. On their optical colour-magnitude diagrams (CMDs), bright CVs lie close to the MS and faint CVs close to the WD cooling sequence, being R ≈ 21.5 mag the cut-off between both populations. Interestingly, in the non-core-collapsed clusters 47 Tuc and ω Cen, only one CV population is observed, and is mainly composed of faint CVs.Another interesting distinction between bright and faint CVs in core-collapsed GCs is related to the level of mass segregation, which is intrinsically connected with the GC relaxation time (proxy for the GC dynamical age) and ...

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Section: Discussionsupporting

confidence: 80%

MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters – IV. Cataclysmic variables – properties of bright and faint populations

Belloni

Giersz

Sandoval

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Moreover, within the framework of this initial binary population, the radius-mass relation inferred by Marks & Kroupa (2012 [167]) are in good agreement with the observed density of molecular cloud clumps, star-forming regions and GCs, and provide dynamical evolutionary time-scales for embedded clusters consistent with the life-time of ultra-compact H II regions and the time-scale needed for gas expulsion to be active in observed very young clusters, as based on their dynamical modelling (e.g. Belloni et al 2018a [160], and references therein).…”

Section: Simulations By Belloni Et Al (2019)supporting

confidence: 85%

“…In both cases, the initial mass function is now always preserved, applying a similar procedure as described in section 6.3 of Belloni et al (2017c [40], see also Oh, Kroupa & Pflamm-Altenburg 2015 [158] and Oh & Kroupa 2016 [159]). In addition, the Kroupa initial binary population was substantially improved (Belloni et al 2017c [40], 2018a [160]) in order to, not only solve the problem with respect to GC MS-MS binary distributions, but also provide a good agreement with respect to Galactic-field late-type MS binaries.…”

Section: Simulations By Belloni Et Al (2019)mentioning

confidence: 99%

Properties of Cataclysmic Variables in Globular Clusters

Belloni¹,

Rivera²

2021

Proceedings of the Golden Age of Cataclysmic Variables and Related Objects v — PoS(GOLDEN2019)

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The study of star clusters plays an important role in our understanding of the Universe since these systems are natural laboratories for testing theories of stellar dynamics and evolution. Particularly, globular clusters (GCs) are one of the most important objects for studying the formation and the physical nature of exotic systems which in turn provide basic information and tools that can help us to understand the formation and evolution processes of star clusters themselves, galaxies and, in general, the young Universe. Among the most interesting objects in GCs are the cataclysmic variables (CVs), which are interacting binaries harbouring a white dwarf accreting from a lowmass companion. Since GC densities are sufficiently high that dynamical encounters involving binaries should be common, CV progenitors are expected to be affected by dynamics in some way in the early stages. In this article we review the formation channels and the influence of dynamics on the CV population in GCs. In particular, we review recent progress in numerical simulations. Furthermore, we discuss observational properties of CVs in GCs and the techniques used to identify and study them. We focus the discussion on the multi-wavelength observations carried out with HST and Chandra on the best-studied GCs NGC 6397, NGC 6752, 47 Tucanae and ω Centauri; on the recent spectroscopic findings with MUSE, and on updates regarding the correlation between the number of faint X-ray sources and the cluster stellar encounter rate. Finally, we discuss some observational prospects that might potentially help future investigations.

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“…But the IMF can be deduced from observations as a mathematical hilfskonstrukt (Kroupa and Jerabkova, 2018), to allow calculations and modelling of stellar populations. But in order to do so statistical corrections are necessary to account for the time evolving binary population in the embedded and exposed cluster (Belloni et al, 2017(Belloni et al, , 2018, loss of stars through ejections Oh et al, 2015;Oh and Kroupa, 2016), mergers and gas expulsion, as well as the corrections for the changes in stellar mass through stellar and binary evolution (Sana et al, 2012;Schneider et al, 2015) and energyequipartition-driven stellar-dynamical evolution (Baumgardt and Makino, 2003;Baumgardt et al, 2008).…”

Section: Can the Imf Be Measured?mentioning

confidence: 99%

“…Nevertheless, by dynamical equivalence, any two dynamical structures (e.g. the Plummer model and a filament) lead to comparable dynamical processing of the stars formed within them if the two structures are dynamically equivalent (Kroupa, 1995a;Belloni et al, 2018). By conservation of angular momentum, stars need to form in multiple systems, whereby most form as binaries (Goodwin and Kroupa, 2005) with well defined orbital parameter distributions and internal (eigen) evolutionary processes (Kroupa, 1995b;Belloni et al, 2017).…”

Section: Does the Imf Vary?mentioning

confidence: 99%

The initial mass function of stars and the star-formation rates of galaxies

Kroupa,

Jerabkova

2021

Preprint

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The measured star-formation rates (SFRs) of galaxies comprise an important constraint on galaxy evolution and also on their cosmological boundary conditions. Any available tracer of the SFR depends on the shape of the mass-distribution of formed stars, i.e. on the stellar initial mass function (IMF). The luminous massive stars dominate the observed photon flux while the dim low-mass stars dominate the mass in the freshly formed population. Errors in the number ratio of the massive to low-mass stars lead to errors in SFR measurements and thus to errors concerning the gas-accretion-rates and the gas-consumption time-scales of galaxies. The stellar IMF has traditionally been interpreted to be a scale-invariant probability density distribution function (PDF), but it may instead be an optimal distribution function. In the PDF interpretation, the stellar IMF observed on the stales of individual star clusters is equal to the galaxy-wide IMF (gwIMF) which, by implication, would be invariant. In this Chapter we discuss the fundamental properties of the IMF and of the gwIMF, the nature of both and their systematic variability as indicated by measurements and theoretical expectations, and we discuss the implications for the SFRs of galaxies and on their main sequence. The importance of the putative most-massive-starmass vs stellar-mass-of-the-hosting-embedded-cluster (m max −M ecl ) relation and its possible establish-ment during the proto-stellar formation phase, is emphasised.

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Dynamical equivalence, the origin of the Galactic field stellar and binary population, and the initial radius–mass relation of embedded clusters

Cited by 22 publications

References 55 publications

MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters – IV. Cataclysmic variables – properties of bright and faint populations

MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters – IV. Cataclysmic variables – properties of bright and faint populations

Properties of Cataclysmic Variables in Globular Clusters

The initial mass function of stars and the star-formation rates of galaxies

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