J/MNRAS/473/849 Mass segregation in Galactic stellar clusters (Dib+, 2018)
Structure and mass segregation in Galactic stellar clusters.
Dib S., Schmeja S., Parker R.J.
<Mon. Not. R. Astron. Soc., 473, 849-859 (2018)>
=2018MNRAS.473..849D 2018MNRAS.473..849D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Morphology
Keywords: stars: formation - Galaxy: general -
open clusters and associations: general -
open clusters and associations: individual - Galaxy: stellar content
Abstract:
We quantify the structure of a very large number of Galactic open
clusters and look for evidence of mass segregation for the most
massive stars in the clusters. We characterize the structure and mass
segregation ratios of 1276 clusters in the Milky Way Stellar Cluster
(MWSC) catalogue containing each at least 40 stars and that are
located at a distance of up to ∼2kpc from the Sun. We use an
approach based on the calculation of the minimum spanning tree of the
clusters, and for each one of them, we calculate the structure
parameter Q and the mass segregation ratio {LAMBDA}MSR. Our findings
indicate that most clusters possess a Q parameter that falls in the
range 0.7-0.8 and are thus neither strongly concentrated nor do they
show significant substructure. Only 27 per cent can be considered
centrally concentrated with Q values >0.8. Of the 1276 clusters, only
14 per cent show indication of significant mass segregation
({LAMBDA}MSR>1.5). Furthermore, no correlation is found between the
structure of the clusters or the degree of mass segregation with their
position in the Galaxy. A comparison of the measured Q values for
the young open clusters in the MWSC to N-body numerical simulations
that follow the evolution of the Q parameter over the first 10Myr
of the clusters life suggests that the young clusters found in the
MWSC catalogue initially possessed local mean volume densities of
ρ*~=10-100M☉/pc3.
Description:
We analysed 1276 Galactic open clusters with uniform astrophysical
data from the MWSC catalogue and computed their structure parameter Q
and the their mass segregation ratio ({LAMBDA}J10 and
{GAMMA}J10.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 118 1276 Data for the properties of the MWSC survey used
and derived in this study
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See also:
J/A+A/543/A156 : Milky Way global survey of star clusters (Kharchenko+, 2012)
J/A+A/558/A53 : Milky Way global survey of star clusters II (Kharchenko+ 2013)
J/A+A/568/A51 : Milky Way global survey of star clusters III (Schmeja+, 2014)
J/A+A/581/A39 : MWSC IV. 63 new open clusters (Scholz+, 2015)
J/A+A/585/A101 : Milky Way global survey of star clusters V (Kharchenko+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- MWSC Number in the MWSC catalogue
6- 22 A17 --- Cluster name of the cluster
24- 30 F7.3 deg RAdeg Right ascension (J2000)
32- 38 F7.3 deg DEdeg Declination (J2000)
40- 46 F7.3 deg GLON Galactic longitude
48- 54 F7.3 deg GLAT Galactic latitude
56- 59 I4 pc Dist Distance from the Sun
61- 65 F5.3 [yr] logAge Age
67- 73 F7.3 pc Rcore ?=999 Core radius
75- 81 F7.3 pc Rtidal ?=999 Tidal radius
83- 86 I4 --- Nstars Number of stars
88- 92 I5 pc Distc Distance to the Galactic centre
94- 98 I5 pc Distp Distance to the Galactic plane
100-106 F7.3 --- Q Q parameter (1)
108-112 F5.3 --- LJ10 LambdaJ10^ MSR parameter (2)
114-118 F5.3 --- GJ10 GammaJ10^ MSR parameter (3)
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Note (1): Q parameter (Cartwright & Whitworth 2004MNRAS.348..589C 2004MNRAS.348..589C,
2009MNRAS.392..341C 2009MNRAS.392..341C), which is given by Q =l-MST/s-
The parameter combines the normalized correlation length s-, i.e. the men
distance between all stars, and the normalized mean edge length l-MST
derived from the MST. The Q parameter is used to quantify the structure of a
cluster and to distinguish between clusters with a central density
concentration and hierarchical clusters with a fractal substructure.
Note (2): Mass segregation ratio from Allison et al. (2009MNRAS.395.1449A 2009MNRAS.395.1449A),
for nMST=10.
Note (3): Modified mass segregation ratio from Olczak, Spurzem & Henning
(2011A&A...532A.119O 2011A&A...532A.119O), for nMST=10.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 06-Aug-2020