J/MNRAS/489/4367 Radii of the Milky Way globular clusters (Piatti+, 2019)
Characteristic radii of the Milky Way globular clusters.
Piatti A.E., Webb J.J., Carlberg R.G.
<Mon. Not. R. Astron. Soc., 489, 4367-4377 (2019)>
=2019MNRAS.489.4367P 2019MNRAS.489.4367P (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Milky Way ; Optical
Keywords: globular clusters: general - Galaxy: kinematics and dynamics -
Galaxy: structure
Abstract:
We report on the extent of the effects of the Milky Way gravitational
field in shaping the structural parameters and internal dynamics of
its globular cluster population. We make use of a homogeneous,
up-to-date data set with kinematics, structural properties, current
and initial masses of 156 globular clusters. In general, cluster radii
increase as the Milky Way potential weakens; with the core and Jacobi
radii being those which increase at the slowest and fastest rate,
respectively. We interpret this result as the innermost regions of
globular clusters being less sensitive to changes in the tidal forces
with the Galactocentric distance. The Milky Way gravitational field
also seems to have differentially accelerated the internal dynamical
evolution of individual clusters, with those toward the bulge
appearing dynamically older. Finally, we find a subpopulation
consisting of both compact and extended globular clusters (as defined
by their rh/rJ ratio) beyond 8 kpc that appear to have lost a
large fraction of their initial mass lost via disruption. Moreover, we
identify a third group with rh/rJ>0.4, which have lost an even
larger fraction of their initial mass by disruption. In both cases the
high fraction of mass lost is likely due to their large orbital
eccentricities and inclination angles, which lead to them experiencing
more tidal shocks at perigalacticon and during disc crossings.
Comparing the structural and orbital parameters of individual clusters
allows for constraints to be placed on whether or not their evolution
was relaxation or tidally dominated.
Description:
To explore how strongly tides have shaped a cluster's evolution, we
make use of the Galactic positions (X, Y, Z), space velocities (U, V,
W), perigalactic (Rperi), and apogalactic (Rapo) distances, and
initial (Mini) and current (MGC) masses of 156 Milky Way globular
clusters as derived by Baumgardt et al. (2019MNRAS.482.5138B 2019MNRAS.482.5138B). In
their study, Baumgardt et al. (2019MNRAS.482.5138B 2019MNRAS.482.5138B) estimate cluster
positions and velocities using data from Gaia DR2 (Gaia Collaboration,
2018, Cat. I/345). Rperi and Rapo are then determined by
integrating the cluster's orbits assuming the Irrgang et al.
(2013A&A...549A.137I 2013A&A...549A.137I) model of the Milky Way. The structural
properties of each cluster, mainly their core (rc) and half-mass
(rh) radius, are taken from Baumgardt & Hilker
(2018MNRAS.478.1520B 2018MNRAS.478.1520B), who estimate the values by comparing the
density profiles of Galactic globular clusters to a large suite of
direct N-body star cluster simulations. Since the set of orbital and
structural cluster properties have been derived by applying the same
methodology, the catalogue represents the largest homogeneous,
up-to-date data set of the Milky Way globular cluster system.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 71 153 Milky Way globular clusters' parameters
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Globular cluster name
13- 18 F6.2 kpc a Semimajor axis of the globular cluster's
orbit
20- 24 F5.2 kpc e_a Error on a
26- 31 F6.2 pc Rperi Perigalactic distance
33- 37 F5.2 pc e_Rperi Error on Rperi
39- 42 F4.2 --- rh/rJa Ratio of half-mass radius to Jacobi radius
calculated at cluster's semimajor distance
44- 47 F4.2 --- rh/rJRperi Ratio of half-mass radius to Jacobi radius
calculated at cluster's perigalactic
distance
49- 52 F4.2 --- ecc Orbital eccentricity (1)
54- 57 F4.2 --- e_ecc Error on ecc
59- 64 F6.2 deg i Orbit inclination
66- 71 F6.2 deg e_i Error on i
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Note (1): We computed the orbital eccentricity as
e=(Rapo-Rperi)/(Rapo+Rperi), where Rperi and Rapo are the
perigalactic and apogalactic distances.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 16-Jan-2023