J/A+A/683/A165 Evaporation ages of young star clusters (Pelkonen+, 2024)
Evaporation ages: A new dating method for young star clusters.
Pelkonen V.-M., Miret-Roig N., Padoan P.
<Astron. Astrophys. 683, A165 (2024)>
=2024A&A...683A.165P 2024A&A...683A.165P (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, ages
Keywords: stars: kinematics and dynamics -
open clusters and associations: general -
open clusters and associations: individual: beta Pictoris -
open clusters and associations: individual: Tucana-Horologium -
open clusters and associations: individual: Ophiuchus -
open clusters and associations: individual: Upper Scorpius -
Abstract:
The ages of young star clusters are fundamental clocks to constrain
the formation and evolution of pre-main-sequence stars and their
protoplanetary disks and exoplanets. However, dating methods for very
young clusters often disagree, casting doubts on the accuracy of the
derived ages.
We propose a new method to derive the kinematic age of star clusters
based on the evaporation ages of their stars.
The method was validated and calibrated using hundreds of clusters
identified in a supernova-driven simulation of the interstellar medium
forming stars for approximately 40Myr within a 250pc region.
We demonstrate that the clusters' evaporation-age uncertainty can be
as small as about 10% for clusters with a large enough number of
evaporated stars and small but with realistic observational errors. We
have obtained evaporation ages for a pilot sample of ten clusters,
finding a good agreement with their published isochronal ages.
The evaporation ages will provide important constraints for modeling
the pre-main-sequence evolution of low-mass stars, as well as allow
for the star formation and gas-evaporation history of young clusters
to be investigated. These ages can be more accurate than isochronal
ages for very young clusters, for which observations and models are
more uncertain.
Description:
We propose a new method to derive the kinematic age of star clusters
based on the evaporation ages of their stars. We demonstrate that the
clusters' evaporation-age uncertainty can be as small as about 10% for
clusters with a large enough number of evaporated stars and small but
with realistic observational errors. We have obtained evaporation ages
for a pilot sample of ten clusters, finding a good agreement with
their published isochronal ages.
Table 1 contains various age estimates and uncertainties for ten
observed clusters.
Table B1 contains the scaling factors and statistical uncertainties
based on a simulation, depending on the observational errors in
position and velocity, and on the number of evaporated stars.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 94 10 Properties of the clusters considered in
this study
tableb1.dat 28 180 Values of the medians of phieva and sigmaeva for
each error pair in the 1000 Monte-Carlo
realizations, in five bins of neva70
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Cluster name
13- 15 I3 pc d Distance to the cluster
17- 20 F4.1 Myr tCMD CMD age from the PARSEC isochrones used
in this work
22- 24 F3.1 Myr E_tCMD CMD age upper uncertainty
26- 28 F3.1 Myr e_tCMD CMD age lower uncertainty
30- 33 F4.1 Myr tDT Dynamical traceback age
35- 37 F3.1 Myr E_tDT Dynamical traceback age upper uncertainty
39- 41 F3.1 Myr e_tDT Dynamical traceback age lower uncertainty
43- 46 F4.1 Myr t*eva Corrected evaporation age determined in
this work
48- 51 F4.1 Myr E_t*eva Corrected evaporation age upper uncertainty
53- 56 F4.1 Myr e_t*eva Corrected evaporation age lower uncertainty
58- 61 F4.2 pc sigmap Observational error in position
63- 66 F4.2 km/s sigmav Observational error in velocity
68- 71 F4.1 pc R50 Core radius
73- 75 I3 --- Nstars Number of stars used to obtain the CMD and
dynamical traceback ages and the starting
sample for the evaporation ages
77- 78 I2 --- Ndiv Number of divergent stars
80- 81 I2 --- Neva Number of evaporated star
83- 84 I2 --- Neva70 Number of stars used to compute the
evaporation age
86- 89 F4.2 --- phieva Correction factor of the evaporation age
(see App. B)
91- 94 F4.2 --- sigmaeva Correction factor uncertainty of the
evaporation age (see App. B)
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- neva70 Lower limit of the n_eva,70 bin
5- 8 F4.2 pc sigmsp Total observational error in position
11- 14 F4.2 km/s sigmav Total observational error in velocity
17- 21 F5.3 --- phieva Scaling factor phi_eva
24- 28 F5.3 --- sigmaeva Statistical uncertainty sigma_eva
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History:
From Veli Matti Pelkonen, veli.matti.pelkonen(at)gmail.com
Acknowledgements:
We thank the anonymous referee for their helpful comments, leading to
an improved and more clear presentation of our work. VMP and PP
acknowledge financial support by the grant PID2020-115892GB-I00,
funded by MCIN/AEI/10.13039/501100011033 and by the grant
CEX2019-000918-M funded by MCIN/AEI/10.13039/501100011033.
(End) Patricia Vannier [CDS] 12-Jan-2024