J/MNRAS/486/5726 80 young open clusters from Gaia DR2 (Dias+, 2019)
The spiral pattern rotation speed of the Galaxy and the corotation radius with
Gaia DR2.
Dias W.S., Monteiro H., Lepine J.R.D., Barros D.A.
<Mon. Not. R. Astron. Soc., 486, 5726-5736 (2019)>
=2019MNRAS.486.5726D 2019MNRAS.486.5726D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Milky Way ; Radial velocities ; Proper motions ;
Positional data ; Parallaxes, trigonometric ; Optical
Keywords: Galaxy: kinematics and dynamics - Galaxy: structure
Abstract:
In this work we revisit the issue of the rotation speed of the spiral
arms and the location of the corotation radius of our Galaxy. This
research was performed using homogeneous data set of young open
clusters (age<50Myr) determined from Gaia Data Release 2 (DR2) data.
The stellar astrometric membership was determined using proper motions
and parallaxes, taking into account the full covariance matrix. The
distance, age, reddening, and metallicity of the clusters were
determined by our non-subjective multidimensional global optimization
tool to fit theoretical isochrones to Gaia DR2 photometric data. The
rotation speed of the arms is obtained from the relation between age
and angular distance of the birthplace of the clusters to the
present-day position of the arms. Using the clusters belonging to the
Sagittarius-Carina, Local, and Perseus arms, and adopting the Galactic
parameters R0=8.3kpc and V0=240km/s, we determine a pattern speed
of 28.2±2.1km/s/kpc, with no difference between the arms. This
implies that the corotation radius is Rc=8.51±0.64kpc, close to
the solar Galactic orbit (Rc/R0=1.02±0.07).
Description:
We used the version 3.5 of the DAML02 catalogue (Dias et al.
2002A&A...389..871D 2002A&A...389..871D, Cat. B/ocl) to select 441 clusters with ages
lower than 50Myr. In addition, we also analysed 154 open clusters with
no age determined in DAML02, 31 clusters recently discovered by
Castro-Ginard et al. (2018A&A...618A..59C 2018A&A...618A..59C, Cat. J/A+A/618/A59) and 52
clusters discovered by Cantat-Gaudin et al. (2018A&A...618A..93C 2018A&A...618A..93C, Cat.
J/A+A/618/A93), looking for young open clusters. We performed the
isochrone fit to the stars with membership greater than 0.51 in order
to select the clusters younger than 50Myr to compose our sample.
For each cluster we searched for the stars in the Gaia DR2 catalogue,
using the central coordinates and the radius taken from the DAML02
catalogue. Since the cluster's radius may be larger than that given in
the catalogue (see Gaia Collaboration et al. 2017A&A...601A..19G 2017A&A...601A..19G, Cat.
J/A+A/601/A19) we opted to use a region in the sky about 2arcmin
bigger than the area covered by the cluster. However, for the clusters
with an apparent diameter less than 5arcmin we searched for stars in
an area four times the cluster area. In this way, we include virtually
all possible members of the studied clusters.
As we use only the clusters with parameters estimated using Gaia DR2
data to compose a homogeneous sample, this was a limiting criterion.
In the final sample of 80 open clusters, 15 clusters have their radial
velocity determined for the first time. In Table 2, we present the
mean proper motion, mean parallax, and mean radial velocity with the
respective errors represented by the one standard deviation of the
open clusters. The distance and age were obtained by fitting Padova
theoretical isochrones (Bressan et al. 2012MNRAS.427..127B 2012MNRAS.427..127B) to
clusters, applying the cross-entropy continuous multi-extremal
optimization method, which takes into account Gaia DR2 photometric
data guided by the astrometric membership. The final fit results
obtained for each cluster are presented in Table 3. Table 4 gives the
present-day (X, Y) and the birthplace (X0, Y0) positions of the
open clusters in the Galactic mid-plane.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 100 80 Results of mean astrometric parameters obtained
using the Gaia DR2 stellar proper motion and
parallaxes
table3.dat 70 80 Results of fundamental parameters obtained from
the isochrone fit
table4.dat 68 80 Present-day and birthplace positions of the open
clusters and their respective errors
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
B/ocl : Optically visible open clusters and Candidates
(Dias+ 2002-2015)
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)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Cluster name
18- 19 I2 h RAh Right ascension (J2000)
21- 22 I2 min RAm Right ascension (J2000)
24- 25 I2 s RAs Right ascension (J2000)
27 A1 --- DE- Declination sign (J2000)
28- 29 I2 deg DEd Declination (J2000)
31- 32 I2 arcmin DEm Declination (J2000)
34- 35 I2 arcsec DEs Declination (J2000)
37- 40 I4 --- Nc Number of cluster stars
42- 46 F5.2 arcmin R Radius used for each cluster to extract the
Gaia DR2 data, centred on the coordinates of
the cluster obtained from visual inspection
48- 52 F5.3 mas plx Mean parallax of the cluster
54- 58 F5.3 mas e_plx 1σ dispersion of the mean parallax
60- 66 F7.3 mas/yr pmRA Mean proper motion in right ascension of the
cluster
68- 72 F5.3 mas/yr e_pmRA 1σ dispersion of pmRA
74- 79 F6.3 mas/yr pmDE Mean proper motion in declination of the
cluster
81- 85 F5.3 mas/yr e_pmDE 1σ dispersion of pmDE
87- 93 F7.3 km/s RV Mean radial velocity of the cluster
95-100 F6.3 km/s e_RV 1σ dispersion of RV
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Cluster name
18- 21 I4 pc Dist Distance
23- 26 I4 pc e_Dist Error on Dist
28- 32 F5.3 [yr] logAge Logarithm of cluster age
34- 38 F5.3 [yr] e_logAge Error on logAge
40- 43 F4.2 mag E(B-V) E(B-V) color excess
45- 48 F4.2 mag e_E(B-V) Error on E(B-V)
50- 53 F4.2 km/s RV Radial velocity
55- 58 F4.2 km/s e_RV Error on RV
60- 64 F5.3 [-] Z Metallicity
66- 70 F5.3 [-] e_Z Error on Z
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Cluster name
18- 23 F6.3 kpc X Present day X position of the open cluster
(x-axis pointing to the Galactic rotation
direction) (1)
25- 29 F5.3 kpc e_X Error on X (2)
31- 36 F6.3 kpc Y Present day Y position of the open cluster
(y-axis positive points towards the Galactic
anticentre) (1)
38- 42 F5.3 kpc e_Y Error on Y (2)
44- 49 F6.3 kpc X0 Birthplace X0 position of the open cluster
(x-axis pointing to the Galactic rotation
direction) (1)
51- 55 F5.3 kpc e_X0 Error on X0 (3)
57- 62 F6.3 kpc Y0 Birthplace Y0 position of the open cluster
(y-axis positive points towards the Galactic
anticentre) (1)
64- 68 F5.3 kpc e_Y0 Error on Y0 (3)
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Note (1): The Sun is situated at (0,8.3) kpc position
Note (2): The errors in the present-day positions were obtained by the usual
propagation formula
Note (3): The errors in the birthplace positions were determined by Monte Carlo
procedure
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 07-Nov-2022