J/AJ/160/279 Untangling the Galaxy. II. Structure within 3kpc (Kounkel+, 2020)
Untangling the Galaxy.
II. Structure within 3kpc.
Kounkel M., Covey K., Stassun K.G.
<Astron. J., 160, 279 (2020)>
=2020AJ....160..279K 2020AJ....160..279K
ADC_Keywords: Milky Way; Clusters, open; Stars, ages; Radial velocities;
Optical
Keywords: Milky Way dynamics ; Galaxy structure ; Stellar kinematics ;
Star clusters ; Stellar associations ; Stellar ages
Abstract:
We present the results of the hierarchical clustering analysis of the
Gaia DR2 data to search for clusters, comoving groups, and other
stellar structures. The current paper builds on the sample from the
previous work, extending it in distance from 1 to 3kpc and increasing
the number of identified structures up to 8292. To aid in the analysis
of the population properties, we developed a neural network called
Auriga to robustly estimate the age, extinction, and distance of a
stellar group based on the input photometry and parallaxes of the
individual members. We apply Auriga to derive the properties of not
only the structures found in this paper, but also previously
identified open clusters. Through this work, we examine the temporal
structure of the spiral arms. Specifically, we find that the
Sagittarius Arm has moved by >500pc in the last 100Myr and the Perseus
Arm has been experiencing a relative lull in star formation activity
over the last 25Myr. We confirm the findings of the previous paper on
the transient nature of the spiral arms, with the timescale of
transition of a few 100Myr. Finally, we find a peculiar ∼1Gyr old
stream of stars that appears to be heliocentric. Its origin is
unclear.
Description:
Previously, in Paper I, we systematically clustered Gaia DR2 data
within |b|<30° and parallax π>1mas using Hierarchical
Density-Based Spatial Clustering of Applications with Noise (HDBSCAN)
to identify 1640 populations containing in total 288370 stars.
Extending the sample beyond 1kpc, we used the same general approach. A
total of ∼82 million stars have been analyzed by HDBSCAN. The final
catalog of clustered structures consists of 987376 stars in 8292
groups, of which 6671 are new from Paper I.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 72 987376 Clustered sources
table2.dat 160 8293 Structure parameters
tablea1.dat 56 1910 Parameters of clusters from
Cantat-Gaudin+, 2018, J/A+A/618/A93
--------------------------------------------------------------------------------
See also:
B/ocl : Optically visible open clusters and Candidates (Dias+, 2002-2015)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/349 : StarHorse, Gaia DR2 photo-astrometric distances (Anders+, 2019)
J/A+A/558/A53 : Milky Way global survey star clusters. II. (Kharchenko+,2013)
J/A+A/618/A93 : Gaia DR2 open clusters in the Milky Way (Cantat-Gaudin+, 2018)
J/AJ/156/84 : APOGEE-2 survey of Orion Complex. II. (Kounkel+, 2018)
J/A+A/623/A108 : Age of 269 GDR2 open clusters (Bossini+, 2019)
J/A+A/624/A126 : New open clusters in Perseus direction (Cantat-Gaudin+, 2019)
J/A+A/627/A35 : New open clusters Galactic anti-centre (Castro-Ginard+, 2019)
J/AJ/158/122 : Local structure & star formation history MW (Kounkel+, 2019)
J/ApJS/245/32 : Newly identified star clusters in Gaia DR2 (Liu+, 2019)
J/A+A/622/L13 : Stellar stream in Gaia DR2 discovery (Meingast+, 2019)
J/A+A/627/A4 : Praesepe (NGC 2632) and its tidal tails (Roeser+, 2019)
J/A+A/621/L2 : Hyades tidal tails revealed by Gaia DR2 (Roeser+, 2019)
J/AJ/160/90 : Stellar parameters for 13196 Kepler dwarfs (Angus+, 2020)
J/A+A/640/A1 : Portrait Galactic disc (Cantat-Gaudin+, 2020)
J/A+A/635/A45 : 570 new open clusters in Galactic disc (Castro-Ginard+, 2020)
J/AJ/159/182 : APOGEE Net YSOs parameters through deep learning (Olney+,2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR2 source identifier
21- 43 F23.19 deg RAdeg [0/360] ICRS Right Ascension (J2015.5)
45- 67 F23.19 deg DEdeg [-90/90] ICRS Declination (J2015.5)
69- 72 I4 --- Group [1/8313] Theia group identifier
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Group [1/8313] Theia group identifier
6- 22 A17 --- OName Other group name
24- 28 A5 --- Str Is the group a string?
30- 34 A5 --- Distinct Is the group distinct?
36- 39 F4.2 [yr] logAge [6.12/9.78] log, Age
41- 44 F4.2 [yr] e_logAge [0.03/0.57] Uncertainty in logAge
46- 49 F4.2 mag AVmag [0.05/4.74] V band reddening
51- 54 F4.2 mag e_AVmag [0.03/0.47] Uncertainty in AVmag
56- 59 I4 pc Dist [48/5166] Distance
61- 65 F5.1 pc e_Dist [1.8/570] Uncertainty in Dist
67- 71 I5 --- Nstars [13/10762] Number of stars
73- 80 F8.4 deg GLON [-38/359] Galactic longitude
82- 89 F8.4 deg GLAT [-29/29] Galactic latitude
91- 96 F6.2 mas/yr pmGLON [-72/67]? proper motion, Galactic longitude (1)
98-103 F6.2 mas/yr pmGLAT [-18/70]? proper motion, Galactic latitude (1)
105-111 F7.2 km/s RVel [-203/157]? Mean radial velocity
113-120 F8.2 pc X [-3248/4963] X position in the heliocentric XYZ
reference frame
122-128 F7.1 pc Y [-3812/4559] Y position in the heliocentric XYZ
reference frame
130-136 F7.1 pc Z [-1916/1677] Z position in the heliocentric XYZ
reference frame
138-144 F7.2 km/s U [-199/124]? U velocity vector, positive toward
the Galactic anticenter (2)
146-152 F7.2 km/s V [-200/85]? V velocity vector, positive in the
direction of Galactic rotation (2)
154-160 F7.2 km/s W [-176/63]? W velocity vector, positive toward
the North Galactic Pole (2)
--------------------------------------------------------------------------------
Note (1): In the local standard of rest
Note (2): In the local standard of rest. Corrected for the bulk
rotation, assuming solar velocity of 220km/s, and the distance to the
galactic center of 8.15kpc (Reid+, 2019ApJ...885..131R 2019ApJ...885..131R).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- Cluster Cluster identification (1)
19- 22 I4 --- Group ? Theia groupe identification (2)
24- 27 F4.2 [yr] logAge log, Age
29- 32 F4.2 [yr] e_logAge Uncertainty in logAge
34- 37 F4.2 mag AVmag V band reddening
39- 42 F4.2 mag e_AVmag Uncertainty in AVmag
44- 50 F7.1 pc Dist Distance
52- 56 F5.1 pc e_Dist Uncertainty in Dist
--------------------------------------------------------------------------------
Note (1): Includes clusters from Cantat-Gaudin+, 2018, J/A+A/618/A93,
Cantat-Gaudin+, 2019, J/A+A/624/A126, Castro-Ginard+, 2019, J/A+A/627/A35,
and Castro-Ginard+, 2020, J/A+A/635/A45.
Note (2): Refers to the closest matched populations in Table 2. Note that
multiple clusters can be associated with the same underling population
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Kounkel et al. Paper I : 2019AJ....158..122K 2019AJ....158..122K cat. J/AJ/158/122
(End) Prepared by [AAS], Coralie Fix [CDS], 16-Feb-2021