YZiCS: On the Mass Segregation of Galaxies in Clusters

Context. Membership analyses of the DANCe and Tycho + DANCe data sets provide the largest and least contaminated sample of Pleiades candidate members to date. Aims. We aim at reassessing the different proposals for the number surface density of the Pleiades in the light of the new and most complete list of candidate members, and inferring the parameters of the most adequate model. Methods. We compute the Bayesian evidence and Bayes Factors for variations of the classical radial models. These include elliptical symmetry, and luminosity segregation. As a by-product of the model comparison, we obtain posterior distributions for each set of model parameters. Results. We find that the model comparison results depend on the spatial extent of the region used for the analysis. For a circle of 11.5 parsecs around the cluster centre (the most homogeneous and complete region), we find no compelling reason to abandon King’s model, although the Generalised King model introduced here has slightly better fitting properties. Furthermore, we find strong evidence against radially symmetric models when compared to the elliptic extensions. Finally, we find that including mass segregation in the form of luminosity segregation in the J band is strongly supported in all our models. Conclusions. We have put the question of the projected spatial distribution of the Pleiades cluster on a solid probabilistic framework, and inferred its properties using the most exhaustive and least contaminated list of Pleiades candidate members available to date. Our results suggest however that this sample may still lack about 20% of the expected number of cluster members. Therefore, this study should be revised when the completeness and homogeneity of the data can be extended beyond the 11.5 parsecs limit. Such a study will allow for more precise determination of the Pleiades spatial distribution, its tidal radius, ellipticity, number of objects and total mass.

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Molecular Dynamics of Extreme Mass Segregation in a Rapidly Collapsing Bubble

Physical Review Letters ◽

10.1103/physrevlett.101.234301 ◽

2008 ◽

Vol 101 (23) ◽

Cited By ~ 25

Author(s):

Alexander Bass ◽

Steven J. Ruuth ◽

Carlos Camara ◽

Barry Merriman ◽

Seth Putterman

Keyword(s):

Molecular Dynamics ◽

Mass Segregation

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Testing multimass dynamical models of star clusters with real data: mass segregation in three Galactic globular clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stw2628 ◽

2016 ◽

Vol 464 (4) ◽

pp. 3871-3881 ◽

Cited By ~ 9

Author(s):

A. Sollima ◽

E. Dalessandro ◽

G. Beccari ◽

C. Pallanca

Keyword(s):

Globular Clusters ◽

Star Clusters ◽

Real Data ◽

Dynamical Models ◽

Galactic Globular Clusters ◽

Mass Segregation

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Photometric, kinematic, and variability study in the young open cluster NGC 1960

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa029 ◽

2020 ◽

Vol 492 (3) ◽

pp. 3602-3621 ◽

Cited By ~ 4

Author(s):

Y C Joshi ◽

J Maurya ◽

A A John ◽

A Panchal ◽

S Joshi ◽

...

Keyword(s):

Open Cluster ◽

Mass Range ◽

Mass Function ◽

Variable Stars ◽

B Stars ◽

V Band ◽

Short Period ◽

Young Open Cluster ◽

Mass Segregation ◽

Variability Study

ABSTRACT We present a comprehensive photometric analysis of a young open cluster NGC 1960 (= M36) along with the long-term variability study of this cluster. Based on the kinematic data of Gaia DR2, the membership probabilities of 3871 stars are ascertained in the cluster field among which 262 stars are found to be cluster members. Considering the kinematic and trigonometric measurements of the cluster members, we estimate a mean cluster parallax of 0.86 ± 0.05 mas and mean proper motions of μRA = −0.143 ± 0.008 mas yr−1 and μDec. = −3.395 ± 0.008 mas yr−1. We obtain basic parameters of the cluster such as E(B − V) = 0.24 ± 0.02 mag, log(Age/yr) = 7.44 ± 0.02, and d = 1.17 ± 0.06 kpc. The mass function slope in the cluster for the stars in the mass range of 0.72–7.32 M⊙ is found to be γ = −1.26 ± 0.19. We find that mass segregation is still taking place in the cluster which is yet to be dynamically relaxed. This work also presents first high-precision variability survey in the central 13 arcmin × 13 arcmin region of the cluster. The V-band photometric data accumulated on 43 nights over a period of more than 3 yr reveals 76 variable stars among which 72 are periodic variables. Among them, 59 are short period (P < 1 d) and 13 are long period (P > 1 d). The variable stars have V magnitudes ranging between 9.1 to 19.4 mag and periods between 41 min and 10.74 d. On the basis of their locations in the H–R diagram, periods, and characteristic light curves, 20 periodic variables belong to the cluster are classified as 2 δ-Scuti, 3 γ-Dor, 2 slowly pulsating B stars, 5 rotational variables, 2 non-pulsating B stars, and 6 as miscellaneous variables.

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Black hole, neutron star, and white dwarf merger rates in AGN discs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2681 ◽

2020 ◽

Vol 498 (3) ◽

pp. 4088-4094 ◽

Cited By ~ 4

Author(s):

B McKernan ◽

K E S Ford ◽

R O’Shaughnessy

Keyword(s):

Black Hole ◽

Compact Object ◽

Relative Number ◽

Expected Number ◽

Lower Mass ◽

Strong Function ◽

Mass Gap ◽

Mass Segregation ◽

The Hill ◽

Mass Functions

ABSTRACT Advanced LIGO and Advanced Virgo are detecting a large number of binary stellar origin black hole (BH) mergers. A promising channel for accelerated BH merger lies in active galactic nucleus (AGN) discs of gas around supermasssive BHs. Here, we investigate the relative number of compact object (CO) mergers in AGN disc models, including BH, neutron stars (NS), and white dwarfs, via Monte Carlo simulations. We find the number of all merger types in the bulk disc grows ∝ t1/3 which is driven by the Hill sphere of the more massive merger component. Median mass ratios of NS–BH mergers in AGN discs are $\tilde{q}=0.07\pm 0.06(0.14\pm 0.07)$ for mass functions (MF) M−1(− 2). If a fraction fAGN of the observed rate of BH–BH mergers (RBH–BH) come from AGN, the rate of NS–BH (NS–NS) mergers in the AGN channel is ${R}_{\mathrm{ BH}\!-\!\mathrm{ NS}} \sim f_{\mathrm{ AGN}}[10,300]\, \rm {Gpc}^{-3}\, \rm {yr}^{-1},({\mathit{ R}}_{NS\!-\!NS} \le \mathit{ f}_{AGN}400\, \rm {Gpc}^{-3}\, \rm {yr}^{-1}$). Given the ratio of NS–NS/BH–BH LIGO search volumes, from preliminary O3 results the AGN channel is not the dominant contribution to observed NS–NS mergers. The number of lower mass gap events expected is a strong function of the nuclear MF and mass segregation efficiency. CO merger ratios derived from LIGO can restrict models of MF, mass segregation, and populations embedded in AGN discs. The expected number of electromagnetic (EM) counterparts to NS–BH mergers in AGN discs at z < 1 is $\sim [30,900]\, {\rm {yr}}^{-1}(f_{\mathrm{ AGN}}/0.1)$. EM searches for flaring events in large AGN surveys will complement LIGO constraints on AGN models and the embedded populations that must live in them.

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