J/AJ/158/122 Local structure & star formation history of the MW (Kounkel+, 2019)
Untangling the Galaxy.
I. Local structure and star formation history of the Milky Way.
Kounkel M., Covey K.
<Astron. J., 158, 122 (2019)>
=2019AJ....158..122K 2019AJ....158..122K (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Associations, stellar ; Stars, ages ;
Morphology ; Positional data ; Parallaxes, trigonometric ;
Proper motions ; Radial velocities ; Space velocities
Keywords: Milky Way dynamics - Galaxy structure - Stellar kinematics -
Stellar associations - Star clusters - Stellar ages
Abstract:
Gaia DR2 (Cat. I/345) provides unprecedented precision in measurements
of the distance and kinematics of stars in the solar neighborhood. Through
applying unsupervised machine learning on DR2's 5D data set (3D position
+ 2D velocity), we identify a number of clusters, associations, and
comoving groups within 1 kpc and |b|<30° (many of which have not been
previously known). We estimate their ages with the precision of ∼0.15 dex.
Many of these groups appear to be filamentary or string-like, oriented
in parallel to the Galactic plane, and some span hundreds of parsec in
length. Most of these string lack a central cluster, indicating that their
filamentary structure is primordial, rather than the result of tidal
stripping or dynamical processing. The youngest strings (<100 Myr) are
orthogonal to the Local Arm. The older ones appear to be remnants of
several other arm-like structures that cannot be presently traced by dust
and gas. The velocity dispersion measured from the ensemble of groups and
strings increase with age, suggesting a timescale for dynamical heating
of ∼300 Myr. This timescale is also consistent with the age at which the
population of strings begins to decline, while the population in more
compact groups continues to increase, suggesting that dynamical processes
are disrupting the weakly bound string populations, leaving only individual
clusters to be identified at the oldest ages. These data shed a new light
on the local galactic structure and a large-scale cloud collapse.
Description:
The catalogues correspond to properties of identified clusters,
associations, and comoving groups within 1 kpc in Gaia DR2 (Cat. I/345).
All sources used for the analysis lie within |b|<30° of the Galactic
plane and parallax>1 mas. The clusters are identified using the Python
implementation of the hierarchical density-based spatial clustering of
applications with noise (HDBSCAN; McInnes et al. 2017JOSS....2..205M 2017JOSS....2..205M).
The final catalog totals 1901 individual groups consisting of 288370 stars
(Table 1). The average properties of the resulting groups are given in
Table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 222 1640 Identified structures and their average properties
table3.dat 149 6907 Traces of the strings
table1.dat 73 288370 Clustered sources
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/585/A101 : Milky Way global survey of star clusters. V.
(Kharchenko+, 2016)
J/A+A/591/A37 : Gaia-ESO Survey. Parameters for cluster members
(Jacobson+, 2016)
J/MNRAS/455/3126 : New Galactic star clusters and candidates (Camargo+, 2016)
J/A+A/618/A59 : Gaia DR2 confirmed new nearby open clusters
(Castro-Ginard+, 2018)
J/A+A/618/A93 : Gaia DR2 open clusters in the Milky Way
(Cantat-Gaudin+, 2018)
J/AJ/157/12 : Star clusters, associations, + candidates in the MW
(Bica+, 2019)
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 [1/1640] Theia group identifier
6- 22 A17 --- OName Other group name
24- 30 F7.5 [yr] logAge [6.14485/9.95276] Log average group age
32- 42 F11.8 mag Av [-0.150042/3.5] Average extinction
44 A1 --- String [y] Is the group a string?
46- 54 F9.5 pc Width [1.07648/142.145] Projected width
56- 64 F9.6 pc Height [0.800295/42.0466] Projected height
66- 74 F9.5 pc Length [36.9384/842.096]? String length
76- 86 F11.7 deg GLON Galactic longitude of string
88- 99 F12.8 deg GLAT Galactic latitude of string
101-108 F8.5 mas plx [1.03705/20.4046] Mean Gaia DR2 parallax
110-120 F11.7 km/s pmGLON [-72.7092/55.5468] Mean proper motion in the
direction of Galactic longitude
122-134 F13.9 km/s pmGLAT [-30.415/31.9572] Mean proper motion in the
direction of Galactic latitude
136-147 F12.8 km/s RV [-69.3919/95.9234]? Mean radial velocity
149-159 F11.6 pc X [-890.577/885.982] X position in the heliocentric
XYZ reference frame
161-172 F12.7 pc Y [-909.901/927.268] Y position in the heliocentric
XYZ reference frame
174-185 F12.7 pc Z [-357.929/294.344] Z position in the heliocentric
XYZ reference frame
187-197 F11.7 km/s U [-69.8636/99.0717]? U velocity vector, positive
toward the Galactic anticenter
199-209 F11.7 km/s V [-61.8764/52.871]? V velocity vector, positive
in the direction of Galactic rotation
211-222 F12.8 km/s W [-30.6367/24.8161]? W velocity vector, positive
toward the North Galactic Pole
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Theia [9/1640] Theia group identifier
6- 10 F5.1 deg GLON Galactic longitude of string
12- 23 F12.8 deg GLAT Galactic latitude of string
25- 34 F10.7 mas plx [1.0416428/13.381758] Average Gaia DR2 parallax
36- 47 F12.8 km/s pmGLON [-42.3994/82.52] Proper motion in the direction
of Galactic longitude
49- 60 F12.8 km/s pmGLAT [-17.027/23.8086] Proper motion in the direction
of Galactic latitude
62- 73 F12.8 km/s RV [-74.975/77.1295] Radial velocity
75- 85 F11.6 pc X [-822.651/916.136] X position in the heliocentric
XYZ reference frame
87- 97 F11.6 pc Y [-949.328/911.592] Y position in the heliocentric
XYZ reference frame
99-110 F12.7 pc Z [-337.227/278.461] Z position in the heliocentric
XYZ reference frame
112-123 F12.8 km/s U [-82.3504/78.9483]? U velocity vector, positive
toward the Galactic anticenter
125-136 F12.8 km/s V [-62.7682/73.4662]? V velocity vector, positive
in the direction of Galactic rotation
138-149 F12.8 km/s W [-32.2203/24.7684]? W velocity vector, positive
toward the North Galactic Pole
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Gaia Gaia DR2 source identifier
21- 43 F23.19 deg RAdeg Right Ascension in decimal degrees (J2000)
45- 68 F24.20 deg DEdeg Declination in decimal degrees (J2000)
70- 73 I4 --- Theia [1/1640] Theia group identifier
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Oct-2019