The Stellar Velocity Distribution in the Solar Neighborhood: Deviations From the Schwarzschild Distribution

Griv, Evgeny; Gedalin, M.; Eichler, David

doi:10.1088/0004-6256/137/3/3520

Cited by 11 publications

(15 citation statements)

References 66 publications

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“…The solid lines are the best-fitting functions of dynamically normal GCs (GCs with upper limit were not included in the fit), while the shaded area represent the 95% confidence of linear regression. The magenta up-triangle marks the Solar neighborhood stars, which has a large scatter in σ among stars of different ages (Griv et al 2009). The blue diamonds represent the two open clusters, with σ = 0.62 ± 0.1 km s −1 for NGC 6791 (Tofflemire et al 2014) and σ = 0.59 +0.07 −0.06 km s −1 for M 67 (Geller et al 2015).…”

Section: Testing the Hills-heggie Lawmentioning

confidence: 99%

A Chandra Survey of Milky Way Globular Clusters. II. Testing the Hills–Heggie Law

Cheng

et al. 2018

ApJ

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Binary-single and binary-binary encounters play a pivotal role in the evolution of star clusters, as they may lead to the disruption or hardening of binaries, a novel prediction of the Hills-Heggie law. Based on our recent Chandra survey of Galactic globular clusters (GCs), we revisit the role of stellar dynamical interactions in GCs, focusing on main-sequence (MS) binary encounters as a potential formation channel of the observed X-ray sources in GCs. We show that the cumulative X-ray luminosity (L X ), a proxy of the total number of X-ray-emitting binaries (primarily cataclysmic variables and coronally active binaries) in a given GC, is highly correlated with the MS binary encounter rate (Γ b ), as L X ∝ Γ 0.77±0.11 b. We further test the Hills-Heggie law against the binary hardness ratio, defined as the relative number of X-ray-emitting hard binaries to MS binaries and approximated by L X /(L K f b ), with L K being the GC K-band luminosity and f b the MS binary fraction. We demonstrate that the binary hardness ratio of most GCs is larger than that of the Solar neighborbood stars, and exhibits a positive correlation with the cluster specific encounter rate (γ), as L X /(L K f b ) ∝ γ 0.65±0.12 . We also find a strong correlation between the binary hardness ratio and cluster velocity dispersion (σ), with L X /(L K f b ) ∝ σ 1.71±0.48 , which is consistent with the Hills-Heggie law. We discuss the role of binary encounters in the context of the Nuclear Star Cluster, arguing that the X-ray-emitting, close binaries detected therein could have been predominatly formed in GCs that later inspiralled to the Galactic center.

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Section: Testing the Hills-heggie Lawmentioning

confidence: 99%

A Chandra Survey of Milky Way Globular Clusters. II. Testing the Hills–Heggie Law

Cheng

et al. 2018

ApJ

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“…Progenitor system winds may run into this environment if the delay time between the formation of the WD and the onset of the accretion is sufficiently short, and if the peculiar velocity of the system is small. The peculiar velocities of stars show a wide range with a typical value of 25-50 km/s for the Galactic plane ( (Griv et al 2009), and references therein). Here, the duration of the wind is given by the evolutionary time scale of the RG phase rather than the time to reach M Ch .…”

Section: Tablementioning

confidence: 99%

SNe Ia AND THEIR ENVIRONMENT: THEORY AND APPLICATIONS TO SN 2014J

Dragulin

Hoêflich

2016

ApJ

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We present theoretical semi-analytic models for the interaction of stellar winds with the interstellar medium (ISM) or prior mass loss implemented in our code SPICE a , assuming spherical symmetry and power-law ambient density profiles and using the Π-theorem. This allows us to test a wide variety of configurations, their functional dependencies, and to find classes of solutions for given observations.Here, we study Type Ia Supernova (SN Ia) surroundings of single and double degenerate systems, and their observational signatures. Winds may originate from the progenitor prior to the white dwarf (WD) stage, the WD, a donor star, or an accretion disk (AD). For M Ch explosions, the AD wind dominates and produces a low-density void several light years across surrounded by a dense shell. The bubble explains the lack of observed interaction in late time SN light curves for, at least, several years. The shell produces narrow ISM lines Doppler shifted by 10-100 km/s, and equivalent widths of ≈ 100 mÅ and ≈ 1 mÅ in case of ambient environments with constant density and produced by prior mass loss, respectively. For SN 2014J, both mergers and M Ch mass explosions have been suggested based on radio and narrow lines. As a consistent and most likely solution, we find an AD wind running into an environment produced by the RG wind of the progenitor during the pre-WD stage, and a short delay, 0.013 to 1.4 M yr, between the WD formation and the explosion. Our framework may be applied more generally to stellar winds and star-formation feedback in large scale galactic evolution simulations.

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“…Unlike Julian & Toomre (1966) and Goldreich & Lynden‐Bell (1965b), we develop the self‐consistent theory of real instabilities of small spontaneous disturbances (the external potential Φ imp = 0), which grow effectively from noise to observable amplitudes in a time of a few rotational periods of the system under study. The nonlinear interaction of fluid elements (stars) with almost aperiodically growing Jeans‐unstable density waves increases the sound speed (random velocities of stars) via the so‐called non‐resonant dynamical heating on a short time‐scale of only 2–3 disc orbital revolutions (Griv, Gedalin & Eichler 2001, 2009; Griv et al 2002, 2003; Liverts et al 2003; Griv 2006). The latter leads to an eventual stabilization (), unless some effective cooling mechanism of the reconstruction of the wave structure exists.…”

Section: Oscillation Spectrummentioning

confidence: 99%

“…The Jeans gravitational instability transfers energy from the regular circular motion to the random motion in the plane of the system. We refer to Lin & Lau (1979), Bertin (1980), Morozov (1980, 1985), Griv et al (1999, 2001, 2002, 2006, 2008, 2009), Liverts et al (2003), and Griv (2006) for a discussion of the problem.…”

Section: Oscillation Spectrummentioning

confidence: 99%

“…Thus, our theory predicts that in observed differentially rotating, gravitationally (Jeans‐) unstable spiral galaxies the radial scale of spiral structure is about λ crit =1–4 kpc () and Toomre’s Q ‐stability parameter, Q ≈ 2 () 5 . Interestingly, the observed stability number Q of Toomre in relaxed stellar discs of most spiral galaxies lies about Q crit = 2–2.5 (Bottema 1993; Zasov, Khoperskov & Saburova 2011; see Griv et al 1999, 2009 for a discussion). These values agree with the results of N ‐body simulations, which showed that the discs become Jeans‐stable for Q ≳ 2 (Hohl 1972; Tomley, Cassen & Steiman‐Cameron 1991; Griv & Chiueh 1998; Khoperskov et al 2003; Liverts et al 2003).…”

Section: Astronomical Implicationsmentioning

confidence: 99%

See 1 more Smart Citation

Stability of galactic discs: finite arm-inclination and finite-thickness effects★

Griv¹,

Gedalin²

2012

Monthly Notices of the Royal Astronomical Society

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A modified theory of the Lin–Shu density waves, studied in connection with the problem of spiral pattern of rapidly and differentially rotating disc galaxies, is presented for both the axisymmetric and non‐axisymmetric structures in highly flattened galaxies resulted from the classical Jeans instability of small gravity perturbations (e.g. those produced by a spontaneous disturbance). A new method is provided for the analytical solution of the self‐consistent system of the gas‐dynamic equations and the Poisson equation describing the stability of a three‐dimensional galactic disc composed of stars or gaseous clouds. In order to apply the method, the modifications introduced for the properties of the gravitationally unstable, that is to say, amplitude‐growing density waves are considered by removing the often used assumptions that the gravity perturbations are axisymmetric and the disc is infinitesimally thin. In contrast to previous studies, in this paper these two effects – the non‐axial symmetry effect and the finite thickness effect – are simultaneously taken into account. We show that non‐axisymmetric perturbations developing in a differentially rotating disc are more unstable than the axisymmetric ones. We also show that destabilizing self‐gravity is far more ‘dangerous’ in thin discs than in thick discs. The primary effect of small but finite thickness is a reduction of the growth rate of the gravitational Jeans instability and a shift in the threshold of instability towards a longer wavelength (and larger wavelength will include more mass). The results of this paper are in qualitative agreement with previous analytical and numerical estimations of the effects. The extent to which our results on the disc’s stability can have a bearing on observable spiral galaxies, including the Milky Way, is also discussed.

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The Stellar Velocity Distribution in the Solar Neighborhood: Deviations From the Schwarzschild Distribution

Cited by 11 publications

References 66 publications

A Chandra Survey of Milky Way Globular Clusters. II. Testing the Hills–Heggie Law

A Chandra Survey of Milky Way Globular Clusters. II. Testing the Hills–Heggie Law

SNe Ia AND THEIR ENVIRONMENT: THEORY AND APPLICATIONS TO SN 2014J

Stability of galactic discs: finite arm-inclination and finite-thickness effects★

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