Structural parameters of 11 faint Galactic globular clusters  derived with 2MASS

Abstract Over the last few decades, exhaustive surveys of extra Galactic globular clusters (EGGCs) have become feasible. Only recently, limited kinematical information of globular clusters (GCs) were available through Gaia DR2 spectroscopy and also proper motions. On the other hand, simulations of GCs can provide detailed information about the dynamical evolution of the system. We present a preliminary study of EGGCs- properties for different dynamical evolutionary stages. We apply this study to 12 Gyr-old GCs simulated as part of the MOCCA Survey Database. Mimicking observational limits, we consider only a subssample of the models in the database, showing that it is possible to represent observed Milky Way GCs. In order to distinguish between different dynamical states of EGGCs, at least three structural parameters are necessary. The best distinction is achieved by considering the central parameters, those being observational core radius, central surface brightness, ratio between central and half-mass velocity dispersion, or similarly considering the central color, the central V magnitude and the ratio between central and half-mass radius velocity dispersion, although such properties could be prohibitive with current technologies. A similar but less solid result is obtained considering the average properties at the half-light radius, perhaps accessible presently in the Local Group. Additionally, we mention that the color spread in EGGCs due to internal dynamical models, at fixed metallcity, could be just as important due to the spread in metallicity.

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Empirical estimates of the Na–O anti-correlation in 95 Galactic globular clusters

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935110 ◽

2019 ◽

Vol 624 ◽

pp. A24 ◽

Cited By ~ 7

Author(s):

Eugenio Carretta

Keyword(s):

Globular Clusters ◽

Structural Parameters ◽

Stellar Populations ◽

Red Giants ◽

Light Elements ◽

Empirical Estimates ◽

Bivariate Correlation ◽

Identity Line ◽

Consistent Picture ◽

Galactic Globular Clusters

Large star-to-star abundance variations are direct evidence of multiple stellar populations in Galactic globular clusters (GCs). The main and most widespread chemical signature is the anti-correlation of the stellar Na and O abundances. The interquartile range (IQR) of the [O/Na] ratio is well suited to quantifying the extent of the anti-correlation and to probe its links to global cluster parameters. However, since it is quite time consuming to obtain precise abundances from spectroscopy for large samples of stars in GCs, here we show empirical calibrations of IQR[O/Na] based on the O, Na abundances homogeneously derived from more than 2000 red giants in 22 GCs in our FLAMES survey. We find a statistically robust bivariate correlation of IQR as a function of the total luminosity (a proxy for mass) and cluster concentration c. Calibrated and observed values lie along the identity line when a term accounting for the horizontal branch (HB) morphology is added to the calibration, from which we obtained empirical values for 95 GCs. Spreads in proton-capture elements O and Na are found for all GCs in the luminosity range from MV = −3.76 to MV = −9.98. This calibration reproduces in a self-consistent picture the link of abundance variations in light elements with the He enhancements and its effect on the stellar distribution on the HB. We show that the spreads in light elements seem already to be dependent on the initial GC masses. The dependence of IQR on structural parameters stems from the well known correlation between c and MV, which is likely to be of primordial origin. Empirical estimates can be used to extend our investigation of multiple stellar populations to GCs in external galaxies, up to M 31, where even integrated light spectroscopy may currently provide only a hint of such a phenomenon.

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Galactic Globular Clusters: A new catalog of masses, structural parameters, velocity dispersion profiles, proper motions and space orbits

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319006823 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 451-454 ◽

Cited By ~ 2

Author(s):

Michael Hilker ◽

Holger Baumgardt ◽

Antonio Sollima ◽

Andrea Bellini

Keyword(s):

Globular Clusters ◽

Velocity Dispersion ◽

Structural Parameters ◽

Large Set ◽

Proper Motions ◽

Density Profiles ◽

Fundamental Parameters ◽

Initial Cluster ◽

Galactic Globular Clusters ◽

Dependent Mass

AbstractWe collected radial velocities of more than 50.000 individual stars in 156 Galactic globular clusters (GGC) and matched them with HST photometry and Gaia DR2 proper motions. This allowed us to derive the GGC’s mean proper motions and space velocities. By fitting a large set of N-body simulations to their velocity dispersion and surface density profiles, combined with new measurements of their internal radially dependent mass functions, we have determined their present-day masses and structural parameters, and for 144 GGCs their internal kinematics. We also derive the initial cluster masses by calculating the cluster orbits backwards in time applying suitable recipes to account for mass-loss and dynamical friction. The new fundamental parameters of GGCs are publicly available via an online database, which will regularly be updated.

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