J/A+A/690/A16 Nearby open clusters empirical isochrone (Rottensteiner+, 2024)
An empirical isochrone archive for nearby open clusters.
Rottensteiner A., Meingast S.
<Astron. Astrophys. 690, A16 (2024)>
=2024A&A...690A..16R 2024A&A...690A..16R (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Associations, stellar ;
Isochrones
Keywords: methods: data analysis - methods: statistical -
stars: Hertzsprung-Russel and C-M diagrams -
open clusters and associations: general
Abstract:
The ages of star clusters and co-moving stellar groups contain
essential information about the Milky Way. Their special properties
and placement throughout the galactic disk make them excellent tracers
of galactic structure and key components to unlocking its star
formation history. Yet, even though the importance of stellar
population ages has been widely recognized, their determination
remains a challenging task often associated with highly
model-dependent and uncertain results. We propose a new approach to
this long-standing problem, which relies on empirical isochrones of
known clusters extracted from high-quality observational data. These
purely observation-based data products open up the possibility of
relative age determination, free of stellar evolution model
assumptions. For the derivation of the empirical isochrones, we used a
combination of the statistical analysis tool principal component
analysis for preprocessing and the supervised machine learning method
support vector regression for curve extraction. To improve the
statistical reliability of our result, we defined the empirical
isochrone of a color-magnitude diagram (CMD) of a cluster as the
median calculated from a set of nboot=1000 curves derived from
bootstrapped data. The algorithm requires no physical priors, is
computationally fast, and can easily be generalized over a large range
of CMD combinations and evolutionary stages of clusters. We provide
empirical isochrones in all Gaia DR2 and DR3 color combinations for 83
nearby clusters (d<500pc), which cover an estimated age range of 7Myr
to 3Gyr. In doing so, we pave the way for a relative comparison
between individual stellar populations based on an age-scaling ladder
of empirical isochrones of known clusters. Furthermore, due to the
exceptional precision of the available observational data, we report
accurate lower main sequence empirical isochrones for many clusters in
our sample, which are of special interest as this region is known to
be especially complex to model. We validate our method and results by
comparing the extracted empirical isochrones to cluster ages in the
literature. We also investigate the added information that empirical
isochrones covering the lower main sequence can provide on case
studies of the IC 4665 cluster and the Meingast 1 stream. The archive
of empirical isochrones offers a novel approach to validating age
estimates and can be used as an age-scaling ladder or age brackets for
new populations and serve as calibration data for further constraining
stellar evolution models.
Description:
Table B1 (Empirical_isochrones). This table contains the derived
empirical isochrones for 83 open clusters and stellar agglomerates, as
well as the respective upper and lower confidence bounds. The
isochrones are provided for the three passband combinations G-BP vs.
abs G, BP_RP vs. abs G, and G-RP vs. abs G for both the Gaia DR3 and
DR2 data sets. Furthermore, we publish empirical isochrones for six
CMD combinations of the grizyJHK passbands of the DANCe dataset for
the Pleiades and IC 4665 clusters (Olivares et al.,
2018A&A...617A..15O 2018A&A...617A..15O, Cat. J/A+A/617/A15; Miret-Roig et al.,
2019A&A...631A..57M 2019A&A...631A..57M, Cat. J/A+A/631/A57). Additionally, the reference
age and source used in the manuscript are listed for each empirical
isochrone.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 186 230536 Empirical isochrones for 83 clusters
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See also:
J/A+A/633/A99 : Gaia DR2 open clusters in the Milky Way. II
(Cantat-Gaudin+, 2020)
J/A+A/645/A84 : Coronae of nearby star clusters (Meingast+, 2021)
J/A+A/677/A59 : SigMA clusters in Sco-Cen (Ratzenboeck+, 2023)
J/AJ/158/77 : Candidates and members of the Pisces-Eridanus stream
(Curtis+, 2019)
J/A+A/624/L11 : Coma Berenices neighbor moving group (Fuernkranz+, 2019)
J/A+A/639/A64 : Extended Meingast 1 source catalogue (Ratzenboeck+, 2020)
J/A+A/617/A15 : Membership probabilities of Pleiades objects (Olivares+, 2018)
J/A+A/631/A57 : IC 4665 DANCe (Miret-Roig+, 2019)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Cluster Cluster name (1)
15- 19 A5 --- Catalog Dataset/Photometric system (DANCe, DR2 or DR3)
21- 25 A5 --- ColFilt Filters used for the CMD color axis
27 A1 --- AbsmagFilt [GJiry] Filter for the CMD absolute magnitude
29- 49 E21.15 mag isox x coordinate of the empirical isochrone
51- 71 E21.15 mag isoy y coordinate of the empirical isochrone
73- 93 E21.15 mag lbx x coordinate of the lower confidence bound
95-115 E21.15 mag lby y coordinate of the lower confidence bound
117-137 E21.16 mag ubx x coordinate of the upper confidence bound
139-159 E21.12 mag uby y coordinate of the upper confidence bound
161-167 F7.5 [yr] logAge Reference age in log units
169-186 A18 --- r_logAge Literature source for reference age (2)
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Note (1): The cluster names are consistent with those used in the original
publications of the cluster membership data.
Catalog references:
Catalog reference I, Gaia DR2 open clusters in the Milky Way,
Cantat-Gaudin et al., 2020A&A...633A..99C 2020A&A...633A..99C, Cat. J/A+A/633/A99
Catalog reference II, Coronae of nearby star clusters,
Meingast et al., 2021A&A...645A..84M 2021A&A...645A..84M, Cat. J/A+A/645/A84
Catalog reference III, SigMA clusters in Sco-Cen,
Ratzenboeck et al., 2023A&A...677A..59R 2023A&A...677A..59R, Cat. J/A+A/677/A59
Catalog reference IV, Coma Berenices neighbor moving group,
Fuernkranz et al., 2019A&A...624L..11F 2019A&A...624L..11F, Cat. J/A+A/624/L11
Catalog reference V, Meingast 1,
Ratzenboeck et al., 2020A&A...639A..64R 2020A&A...639A..64R, Cat. J/A+A/639/A64
Note (2): References as follows:
Cantat-Gaudin+2020 = 2020A&A...633A..99C 2020A&A...633A..99C, Cat. J/A+A/633/A99
Curtis+2019 = 2019AJ....158...77C 2019AJ....158...77C, Cat. J/AJ/158/77
Dias+2021 = 2021MNRAS.504..356D 2021MNRAS.504..356D, Cat. J/MNRAS/504/356
Ratzenbeck+2023 = 2023A&A...678A..71R 2023A&A...678A..71R, Cat. J/A+A/678/A71
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Acknowledgements:
Alena Rottensteiner, alena.kristina.rottensteiner(at)univie.ac.at
Stefan Meingast, stefan.meingast(at)univie.ac.at
(End) A. Rottensteiner [ESO, Vienna Univ.], P. Vannier [CDS] 26-Jun-2024