J/ApJ/936/154 HSTPROMO. VII. Velocity dispertion profiles (Watkins+, 2022)
Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular
Clusters.
VII. Energy Equipartition.
Watkins L.L., van der Marel R.P., Libralato M., Bellini A., Anderson J.,
Alfaro-Cuello M.
<Astrophys. J., 936, 154 (2022)>
=2022ApJ...936..154W 2022ApJ...936..154W
ADC_Keywords: Clusters, globular; Stars, masses; Optical
Keywords: Globular star clusters ; Proper motions ; Stellar dynamics ;
Stellar kinematics
Abstract:
We examine the degree of energy equipartition in nine Galactic
globular clusters using proper motions measured with the Hubble Space
Telescope. For most clusters in the sample, this is the first energy
equipartition study ever performed. This study is also the largest of
its kind, albeit with only nine clusters. We begin by rigorously
cleaning the catalogs to remove poor-quality measurements and to
ensure high signal to noise for the study. Using the cleaned catalogs,
we investigate how velocity dispersion σ changes with stellar
mass m. We fit two functional forms: the first, a classic power law of
the form σ∝m-η where η is the degree of energy
equipartition, and the second from Bianchini et al. parameterized by
an equipartition mass meq where η changes with stellar mass. We
find that both functions fit well but cannot distinguish with
statistical significance which function provides the best fit. All
clusters exhibit varying degrees of partial equipartition; no cluster
is at or near full equipartition. We search for correlations of η
and meq with various cluster properties. The most significant
correlation is observed with the number of core or median relaxation
times (Ncore or Nhalf) the cluster has experienced. Finally, we
determine the radial equipartition profile for each cluster, that is,
how the degree of equipartition changes with projected distance from
the cluster center. We do not detect statistically significant trends
in the degree of equipartition with radius. Overall, our observational
findings are in broad agreement with theoretical predictions from
N-body models published in recent years.
Description:
We have studied the stellar kinematics as a function of stellar mass
in nine Galactic GCs using PMs measured with HST, and in so doing,
studied their degree of energy equipartition.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 79 90 Binned velocity dispersion profiles as a function
of stellar mass
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See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/ApJ/710/1032 : Proper motions in ω Cen (Anderson+, 2010)
J/ApJ/797/115 : HSTPROMO I. Observations and NGC7078 results (Bellini+, 2014)
J/MNRAS/444/392 : Synthetic Stellar Photometry. I. (Casagrande+, 2014)
J/ApJ/803/29 : HSTPROMO catalogs. II. Kinematic profiles (Watkins+, 2015)
J/ApJ/812/149 : HSTPROMO. III. Dynamical distances (Watkins+, 2015)
J/ApJ/827/12 : HSTPROMO cat of GCs IV. Blue straggler stars (Baldwin+, 2016)
J/ApJ/853/86 : HST large programme on ω Centauri. II. (Bellini+, 2018)
J/ApJ/861/99 : HSTPROMO cat. VI. Improved analysis NGC362 (Libralato+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Cluster name
9- 10 I2 --- Bin [1/10] bin number
12- 15 I4 --- Nstar [224/7982] number of stars in bin
17- 30 F14.12 Msun Mass [0.28/0.86] average stellar mass in bin
32- 47 F16.14 Msun e_Mass [0.003/0.07] spread in Mass
49- 62 F14.12 mas/yr sigma [0.17/0.73] velocity dispersion in bin
64- 79 F16.14 mas/yr e_sigma [0.004/0.03] uncertainty on sigma
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History:
From electronic version of the journal
References:
Bellini et al. Paper I : 2014ApJ...797..115B 2014ApJ...797..115B Cat. J/ApJ/797/115
Watkins et al Paper II : 2015ApJ...803...29W 2015ApJ...803...29W Cat. J/ApJ/803/29
Watkins et al. Paper III : 2015ApJ...812..149W 2015ApJ...812..149W Cat. J/ApJ/812/149
Baldwin et al. Paper IV : 2016ApJ...827...12B 2016ApJ...827...12B Cat. J/ApJ/827/12
Bellini et al. Paper V : 2017ApJ...844..167B 2017ApJ...844..167B
Libralato et al. Paper VI : 2018ApJ...861...99L 2018ApJ...861...99L Cat. J/ApJ/861/99
(End) Prepared by [AAS], Coralie Fix [CDS], 28-Jun-2024