J/MNRAS/444/290 Star clusters distances and extinctions. II. (Buckner+, 2014)
Properties of star clusters. II. Scaleheight evolution of clusters.
Buckner A.S.M., Froebrich D.
<Mon. Not. R. Astron. Soc., 444, 290-302 (2014)>
=2014MNRAS.444..290B 2014MNRAS.444..290B
ADC_Keywords: Associations, stellar ; Clusters, open ; Stars, distances ;
Extinction
Keywords: Galaxy: evolution - Galaxy: general -
open clusters and associations: general - Galaxy: structure -
galaxies: star clusters: general
Abstract:
Until now, it has been impossible to observationally measure how star
cluster scaleheight evolves beyond 1Gyr as only small samples have
been available. Here, we establish a novel method to determine the
scaleheight of a cluster sample using modelled distributions and
Kolmogorov-Smirnov tests. This allows us to determine the scaleheight
with a 25% accuracy for samples of 38 clusters or more. We apply
our method to investigate the temporal evolution of cluster
scaleheight, using homogeneously selected sub-samples of Kharchenko et
al. (MWSC, 2012, Cat. J/A+A/543/A156, 2013, J/A+A/558/A53 ), Dias et
al. (DAML02, 2002A&A...389..871D 2002A&A...389..871D, Cat. B/ocl), WEBDA, and Froebrich et
al. (FSR, 2007MNRAS.374..399F 2007MNRAS.374..399F, Cat. J/MNRAS/374/399). We identify a
linear relationship between scaleheight and log(age/yr) of clusters,
considerably different from field stars. The scaleheight increases
from about 40pc at 1Myr to 75pc at 1Gyr, most likely due to internal
evolution and external scattering events. After 1Gyr, there is a
marked change of the behaviour, with the scaleheight linearly
increasing with log(age/yr) to about 550pc at 3.5Gyr. The most likely
interpretation is that the surviving clusters are only observable
because they have been scattered away from the mid-plane in their
past. A detailed understanding of this observational evidence can only
be achieved with numerical simulations of the evolution of cluster
samples in the Galactic disc. Furthermore, we find a weak trend of an
age-independent increase in scaleheight with Galactocentric distance.
There are no significant temporal or spatial variations of the cluster
distribution zero-point. We determine the Sun's vertical displacement
from the Galactic plane as Z☉=18.5±1.2pc.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 71 298 Summary table of the FSR cluster properties
determined with our isochrone-fitting pipeline
--------------------------------------------------------------------------------
See also:
J/MNRAS/374/399 : Infrared star clusters with |b|<20° (Froebrich+, 2007)
J/MNRAS/409/1281 : Old star clusters in the FSR catalogue (Froebrich+, 2010)
J/MNRAS/436/1465 : Star clusters distances and extinctions (Buckner+, 2013)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- FSR [32/1738] FSR number, <[FSR2007] NNNN> in Simbad
6- 10 A5 --- Type Known open cluster or New cluster
12- 14 A3 --- Class [OC PMS] Cluster class: OC (open cluster) or
PMS (contains pre-Main-Sequence stars)
16- 21 F6.2 deg GLON Galactic longitude
23- 28 F6.2 deg GLAT Galactic latitude
30- 33 F4.1 kpc DP1 [1.1/11] Distance determined using our
photometric method in Paper I (J/MNRAS/436/1465)
35- 39 F5.2 kpc DP2 [0.4/12] Distance determined using our pipeline
41- 44 F4.2 kpc e_DP2 [0/1] rms uncertainty on DP2
46- 50 F5.2 mag AP1H H-band extinction values calculated from H-K
excess using our photometric method in Paper I
(Buckner & Froebrich 2013, J/MNRAS/436/1465)
52- 55 F4.2 mag AP2H H-band extinction values calculated from H-K
excess using our pipeline
57- 60 F4.2 mag e_AP2H rms uncertainty on AP2H (1)
62- 66 F5.2 [yr] logAge [6.7/10] Age
68- 71 F4.2 [yr] e_logAge [0/0.4] rms uncertainty on logAge (1)
--------------------------------------------------------------------------------
Note (1): note that e_AP2H and e_log(age/yr) are only the statistical variations
of the three isochrone fits and do not account for systematical uncertainties
due to the use of solar metallicity isochrones.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Buckner & Froebrich, Paper I, 2013MNRAS.436.1465B 2013MNRAS.436.1465B, Cat. J/MNRAS/436/1465
(End) Patricia Vannier [CDS] 23-Apr-2015