J/ApJ/936/160 Properties of 328 stellar strings (Zucker+, 2022)
Disconnecting the Dots: Re-examining the Nature of Stellar "Strings" in the
Milky Way.
Zucker C., Peek J.E.G., Loebman S.
<Astrophys. J., 936, 160 (2022)>
=2022ApJ...936..160Z 2022ApJ...936..160Z
ADC_Keywords: Milky Way; Clusters, open
Keywords: Star clusters ; Stellar dynamics ; Interstellar filaments ;
Milky Way Galaxy
Abstract:
Recent analyses of Gaia data have resulted in the identification of
new stellar structures, including a new class of extended stellar
filaments called stellar "strings," first proposed by Kounkel & Covey.
We explore the spatial, kinematic, and chemical composition of strings
to demonstrate that these newfound structures are largely inconsistent
with being physical objects whose members share a common origin.
Examining the 3D spatial distribution of string members, we find that
the spatial dispersion around the claimed string spine does not
improve in the latest Gaia DR3 data release-despite tangible gains in
the signal-to-noise ratio of the parallax measurements-counter to
expectations of a bona fide structure. Using the radial velocity
dispersion of the strings (averaging σVr=16km/s) to estimate
their virial masses, we find that all strings are gravitationally
unbound. Given the finding that the strings are dispersing, the
reported stellar ages of the strings are typically 120x larger than
their measured dispersal times. Finally, we validate prior work that
stellar strings are more chemically homogeneous than their local field
stars but show it is possible to obtain the same signatures of
chemical homogeneity by drawing random samples of stars from
spatially, temporally, and kinematically unrelated open clusters. Our
results show that while some strings may be composed of real
substructures, there is no consistent evidence for larger string-like
connections over the sample. These results underscore the need for
caution in over-interpreting the significance of these strings and
their role in understanding the star formation history of the Milky
Way.
Description:
Kounkel & Covey, 2019, J/AJ/158/122 (hereafter KC19) present a sample
of 328 claimed coeval stellar strings.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 60 328 Spatial and dynamical properties of stellar strings
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)
J/A+A/619/A155 : Open cluster kinematics with Gaia DR2 (Soubiran+, 2018)
J/AJ/158/122 : Local structure & * formation history of MW (Kounkel+, 2019)
J/ApJ/870/32 : Kinematics young star clusters & associations (Kuhn+, 2019)
J/A+A/621/L3 : Hyades tidal tails with Gaia DR2 (Meingast+, 2019)
J/A+A/622/L13 : Stellar stream in Gaia DR2 discovery (Meingast+, 2019)
J/A+A/635/A45 : 570 open clusters in Galactic disc (Castro-Ginard+, 2020)
J/MNRAS/496/2422 : Abundances 42 Pisces-Eridanus stream stars (Hawkins+, 2020)
J/AJ/160/279 : Untangling Galaxy II. Structure within 3kpc (Kounkel+, 2020)
J/A+A/639/A64 : Extended Meingast 1 source catalogue (Ratzenboeck+, 2020)
J/ApJ/904/196 : Stellar parameters of a Young Stellar Snake (Tian, 2020)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
J/A+A/645/A84 : Coronae of nearby star clusters (Meingast+, 2021)
J/MNRAS/503/3279 : GALAH survey Galactic disc with open clusters (Spina+, 2021)
J/A+A/647/A19 : 3D Kinematics and age of OCs (Tarricq+, 2021)
J/AJ/163/275 : Theia 456 stellar stream in Milky Way disk (Andrews+, 2022)
J/ApJ/928/70 : Gaia EDR3 members stars of 55 FoF groups (Coronado+, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Theia [9/1640] Name of the string (1)
6- 7 I2 pc Offset-DR2 [4/94] Median Gaia DR2 distance offset between
stars and spine
9- 11 I3 --- SNR-DR2 [15/221] Median signal-to-noise, Gaia DR2
parallax measurements
13- 15 I3 pc Offset-DR3 [4/107] Median Gaia DR3 distance offset between
stars and spine
17- 19 I3 --- SNR-DR3 [18/478] Median signal-to-noise, Gaia DR3
parallax measurements
21- 24 F4.1 km/s sigma-Vr [3.0/53.2] Error-weighted radial velocity
dispersion (2)
26- 32 E7.1 Msun Mvir [45000/52000000] Predicted virial mass of
string using sigma-Vr
34- 37 I4 Msun Mobs [19/6457] Estimated observed mass of string (3)
39- 45 A7 --- Mvir/Mobs Ratio, predicted virial to observed mass of
string
47- 50 F4.1 Myr tdisp [0.2/12.6] Predicted dispersal time of unbound
string (4)
52- 55 I4 Myr Age [4/8969] Reported string age (5)
57- 60 I4 --- Age/tdisp [3/7885] Ratio, reported age to dispersal time
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Note (1): Name of the string, Kounkel & Covey, 2019, J/AJ/158/122.
Note (2): Error-weighted radial velocity dispersion of the subset of stars
in the string with Gaia DR3 radial velocity data after removing flagged
binaries.
Note (3): Estimated mass of the string, computed by counting the number of
stellar members and assuming a mean stellar mass of 0.61 Msun/member.
Note (4): Predicted dispersal time of the unbound string defined as the
crossing time, Offset-DR3 / sigma-Vr
Note (5): Reported age of the string in Kounkel & Covey+, 2019, J/AJ/158/122K
see their Table 2.
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History:
From electronic version of the journal
References:
Kounkel and Covey, KC19 : 2019AJ....158..122K 2019AJ....158..122K Cat. J/AJ/158/122
(End) Prepared by [AAS], Coralie Fix [CDS], 02-Jul-2024