J/A+A/689/A11 Dynamical age of Octans (Galli+, 2024)
Dynamical traceback age of the Octans young stellar association.
Galli P.A.B., Miret-Roig N., Bouy H., Olivares J., Barrado D.
<Astron. Astrophys. 689, A11 (2024)>
=2024A&A...689A..11G 2024A&A...689A..11G (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Proper motions ; Radial velocities ;
Stars, ages
Keywords: stars: formation - stars: kinematics and dynamics -
Galaxy: kinematics and dynamics - solar neighbourhood -
open clusters and associations: individual: Octans association
Abstract:
Octans is one of the most distant (d∼150pc) young stellar associations
of the solar neighbourhood, and it has not yet been sufficiently
explored. Its age is still poorly constrained in the literature and
requires further investigation. We take advantage of the
state-of-the-art astrometry delivered by the third data release of the
Gaia space mission combined with radial velocity measurements obtained
from high-resolution spectroscopy to compute the 3D positions and 3D
spatial velocities of the stars and derive the dynamical traceback age
of the association. We created a clean sample of cluster members by
removing potential outliers from our initial list of candidate
members. We then performed an extensive traceback analysis using
different subsamples of stars, different metrics to define the size of
the association, and different models for the Galactic potential to
integrate the stellar orbits in the past. We derive a dynamical age of
34+2-2Myr that is independent from stellar models and represents
the most precise age estimate currently available for the Octans
association. After correcting the radial velocity of the stars for the
effect of gravitational redshift, we obtain a dynamical age of
33+3-1Myr, which is in very good agreement with our first
solution. This shows that the effect of gravitational redshift is
small for such a distant young stellar association. Our result is also
consistent with the less accurate age estimates obtained in previous
studies from lithium depletion (30-40Myr) and isochrones (20-30Myr).
By integrating the stellar orbits in time, we show that the members of
Octans and Octans-Near had different locations in the past, which
indicates that the two associations are unrelated despite the close
proximity in the sky. This is the first reliable and precise dynamical
age result for the Octans young stellar association. Our results
confirm that it is possible to derive precise dynamical ages via the
traceback method for ∼30 Myr old stellar clusters at about ∼150 pc
with the same precision level that has been achieved in other studies
for young stellar groups within 50 pc of the Sun. This represents one
more step towards constructing a self-consistent age scale based on
the 3D space motion of the stars in the young stellar clusters of the
solar neighbourhood.
Description:
Properties of Octans stars (astrometry, photometry, radial velocities
derived in this study and youth indicators).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 90 85 Radial velocities derived in this paper
tablea2.dat 119 103 Properties of Octans stars
tablea3.dat 70 103 Youth indicators of Octans stars
tablea4.dat 199 29 Positions and velocities at present and birth time
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Source identifier from Gaia-DR3 catalogue
21- 32 F12.8 deg RAdeg Right ascension (ICRS) at Ep=2016.0
34- 44 F11.7 deg DEdeg Declination (ICRS) at Ep=2016.0
46- 52 F7.1 d MJD Modified Julian date
54- 59 F6.2 km/s RV Radial velocity
61- 64 F4.2 km/s e_RV Radial velocity uncertainty
66- 69 F4.2 km/s s_RV Radial velocity scatter
71- 81 A11 --- PID Programme identifier
83- 88 A6 --- Inst Instrument
90 I1 --- Flag [0/1] Binary flag (0=single; 1=binary)
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Source identifier from Gaia-DR3 catalogue
21- 32 F12.8 deg RAdeg Right ascension (ICRS) at Ep=2016.0
34- 44 F11.7 deg DEdeg Declination (ICRS) at Ep=2016.0
46- 52 F7.3 mas/yr pmRA Proper motion in right ascension
54- 58 F5.3 mas/yr e_pmRA Proper motion uncertainty in right ascension
60- 66 F7.3 mas/yr pmDE Proper motion in declination
68- 72 F5.3 mas/yr e_pmDE Proper motion uncertainty in declination
74- 79 F6.3 mas plx Parallax
81- 85 F5.3 mas e_plx Parallax uncertainty
87- 92 F6.2 km/s RV1 ?=- Radial velocity (Gaia-DR3)
95- 98 F4.2 km/s e_RV1 ?=- Radial velocity uncertainty (Gaia-DR3)
101-105 F5.2 km/s RV2 ?=- Radial velocity (this paper)
107-111 F5.2 km/s e_RV2 ?=- Radial velocity uncertainty (this paper)
113 I1 --- Flag1 [0/1] Binary flag (0=single; 1=binary)
115 I1 --- Flag2 [0/1] Sample flag (0=rejected; 1=accepted)
117 I1 --- Flag3 [0/1] Control sample 1
(0=rejected; 1=accepted)
119 I1 --- Flag4 [0/1] Control sample 2
(0=rejected; 1=accepted)
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Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Source identifier from Gaia-DR3 catalogue
21- 26 F6.3 mag Gmag G-band magnitude (Gaia-DR3)
28- 33 F6.3 mag Jmag ?=- J-band magnitude (2MASS)
35- 40 F6.3 mag NUV ?=- NUV magnitude (GALEX)
42- 47 F6.3 --- HR1 ?=- Hardness ratio 1 (1)
49- 53 F5.3 --- MIR ?=- Mid-infrared excess significance (2)
55- 57 I3 0.1pm EWLi ?=- Lithium equivalent width (mÅ)
59- 68 A10 --- Youth List of youth indicators
70 I1 --- Flag [0/1] Final membership (0=rejected; 1=accepted)
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Note (1): HR1 ratio from
2RXS (BOLLER et al., 2016A&A...588A.103B 2016A&A...588A.103B, Cat. J/A+A/588/A103) or
4XMM-DR13 (Webb et al., 2020A&A...641A.136W 2020A&A...641A.136W, Cat. IX/69).
Note (2): Mid-infrared excess significance from
McDonald et al., 2017MNRAS.471..770M 2017MNRAS.471..770M, Cat. J/MNRAS/471/770).
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Source identifier from Gaia-DR3 catalogue
22- 26 F5.1 pc X0 X coordinate (present time)
29- 31 F3.1 pc e_X0 X coordinate lower uncertainty (present time)
33- 35 F3.1 pc E_X0 X coordinate upper uncertainty (present time)
37- 42 F6.1 pc Y0 Y coordinate (present time)
45- 47 F3.1 pc e_Y0 Y coordinate lower uncertainty (present time)
49- 51 F3.1 pc E_Y0 Y coordinate upper uncertainty (present time)
54- 58 F5.1 pc Z0 Z coordinate (present time)
61- 63 F3.1 pc e_Z0 Z coordinate lower uncertainty (present time)
65- 67 F3.1 pc E_Z0 Z coordinate upper uncertainty (present time)
69- 72 F4.1 km/s U0 U velocity (present time)
75- 77 F3.1 km/s e_U0 U velocity lower uncertainty (present time)
79- 81 F3.1 km/s E_U0 U velocity upper uncertainty (present time)
83- 85 F3.1 km/s V0 V velocity (present time)
88- 90 F3.1 km/s e_V0 V velocity lower uncertainty (present time)
92- 94 F3.1 km/s E_V0 V velocity upper uncertainty (present time)
96- 99 F4.1 km/s W0 W velocity (present time)
102-104 F3.1 km/s e_W0 W velocity lower uncertainty (present time)
106-108 F3.1 km/s E_W0 W velocity upper uncertainty (present time)
111-114 F4.1 pc X X coordinate (birth time)
117-120 F4.1 pc e_X X coordinate lower uncertainty (birth time)
122-125 F4.1 pc E_X X coordinate upper uncertainty (birth time)
127-132 F6.1 pc Y Y coordinate (birth time)
135-138 F4.1 pc e_Y Y coordinate lower uncertainty (birth time)
140-143 F4.1 pc E_Y Y coordinate upper uncertainty (birth time)
146-149 F4.1 pc Z Z coordinate (birth time)
152-154 F3.1 pc e_Z Z coordinate lower uncertainty (birth time)
156-158 F3.1 pc E_Z Z coordinate upper uncertainty (birth time)
160-163 F4.1 km/s U U velocity (birth time)
166-168 F3.1 km/s e_U U velocity lower uncertainty (birth time)
170-172 F3.1 km/s E_U U velocity upper uncertainty (birth time)
174-176 F3.1 km/s V V velocity (birth time)
179-181 F3.1 km/s e_V V velocity lower uncertainty (birth time)
183-185 F3.1 km/s E_V V velocity upper uncertainty (birth time)
187-190 F4.1 km/s W W velocity (birth time)
193-195 F3.1 km/s e_W W velocity lower uncertainty (birth time)
197-199 F3.1 km/s E_W W velocity upper uncertainty (birth time)
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Acknowledgements:
Phillip Galli, phillip.ab.galli(at)gmail.com
(End) Patricia Vannier [CDS] 12-Jun-2024