scholarly journals Open clusters as tracers on radial migration of the galactic disc

2020 ◽  
Vol 495 (3) ◽  
pp. 2673-2681 ◽  
Author(s):  
Y Q Chen ◽  
G Zhao
Keyword(s):  
Open Clusters ◽  
Important Process ◽  
Galactic Disc ◽  
Migration Distance ◽  
Radial Migration ◽  
Orbital Parameters ◽  
Migration Rates ◽  
Formation History ◽  
Gaia Dr2

ABSTRACT Radial migration is an important process in the Galactic disc. A few open clusters show some evidence on this mechanism but there is no systematic study. In this work, we investigate the role of radial migration on the Galactic disc based on a large sample of 146 open clusters with homogeneous metallicity and age from Netopil et al. and kinematics calculated from Gaia DR2. The birth site Rb, guiding radius Rg, and other orbital parameters are calculated, and the migration distance |Rg − Rb| is obtained, which is a combination of metallicity, kinematics, and age information. It is found that 44 per cent open clusters have |Rg − Rb| < 1 kpc, for which radial migration (churning) is not significant. Among the remaining 56 per cent open clusters with |Rg − Rb| > 1 kpc, young ones with t < 1.0 Gyr tend to migrate inward, while older clusters usually migrate outward. Different mechanisms of radial migration between young and old clusters are suggested based on their different migration rates, Galactic locations, and orbital parameters. For the old group, we propose a plausible way to estimate migration rate and obtain a reasonable value of $1.5 \pm 0.5 \,\rm {kpc\,Gyr}^{ -1}$ based on 10 intermediate-age clusters at the outer disc, where the existence of several special clusters implies its complicate formation history.

scholarly journals Extended halo of NGC 2682 (M 67) from Gaia DR2

2019 ◽  
Vol 627 ◽  
pp. A119 ◽  
Author(s):  
R. Carrera ◽  
M. Pasquato ◽  
A. Vallenari ◽  
L. Balaguer-Núñez ◽  
T. Cantat-Gaudin ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Open Cluster ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Galactic Disc ◽  
The Past ◽  
External Perturbations ◽  
Galactic Potential ◽  
Gaia Dr2

Context. NGC 2682 is a nearby open cluster that is approximately 3.5 Gyr old. Dynamically, most open clusters are expected to dissolve on shorter timescales of ≈1 Gyr. That it has survived until now means that NGC 2682 was likely much more massive in the past and is bound to have an interesting dynamical history. Aims. We investigate the spatial distribution of the stars in NGC 2682 to constrain dynamical evolution of the cluster. We particularly focus on the marginally bound stars in the cluster outskirts. Methods. We used Gaia DR2 data to identify NGC 2682 members up to a distance of ∼150 pc (10°). The two methods Clusterix and UPMASK were applied to this end. We estimated distances to obtain 3D stellar positions using a Bayesian approach to parallax inversion, with an appropriate prior for star clusters. We calculated the orbit of NGC 2682 using the GRAVPOT16 software. Results. The cluster extends up to 200′ (50 pc), which implies that its size is at least twice as large as previously believed. This exceeds the cluster Hill sphere based on the Galactic potential at the distance of NGC 2682. Conclusion. The extra-tidal stars in NGC 2682 may originate from external perturbations such as disc-shocking or dynamical evaporation from two-body relaxation. The former origin is plausible given the orbit of NGC 2682, which crossed the Galactic disc ≈40 Myr ago.

scholarly journals Hunting for open clusters in Gaia DR2: 582 new open clusters in the Galactic disc

2020 ◽  
Vol 635 ◽  
pp. A45 ◽  
Author(s):  
A. Castro-Ginard ◽  
C. Jordi ◽  
X. Luri ◽  
J. Álvarez Cid-Fuentes ◽  
L. Casamiquela ◽  
...  
Keyword(s):  
Machine Learning ◽  
Big Data ◽  
Clustering Algorithm ◽  
Open Cluster ◽  
Open Clusters ◽  
Galactic Disc ◽  
Data Environment ◽  
Blind Search ◽  
Tidal Tails ◽  
Gaia Dr2

Context. Open clusters are key targets for studies of Galaxy structure and evolution, and stellar physics. Since the Gaia data release 2 (DR2), the discovery of undetected clusters has shown that previous surveys were incomplete. Aims. Our aim is to exploit the Big Data capabilities of machine learning to detect new open clusters in Gaia DR2, and to complete the open cluster sample to enable further studies of the Galactic disc. Methods. We use a machine-learning based methodology to systematically search the Galactic disc for overdensities in the astrometric space and identify the open clusters using photometric information. First, we used an unsupervised clustering algorithm, DBSCAN, to blindly search for these overdensities in Gaia DR2 (l, b, ϖ, μα*, μδ), and then we used a deep learning artificial neural network trained on colour–magnitude diagrams to identify isochrone patterns in these overdensities, and to confirm them as open clusters. Results. We find 582 new open clusters distributed along the Galactic disc in the region |b| < 20°. We detect substructure in complex regions, and identify the tidal tails of a disrupting cluster UBC 274 of ∼3 Gyr located at ∼2 kpc. Conclusions. Adapting the mentioned methodology to a Big Data environment allows us to target the search using the physical properties of open clusters instead of being driven by computational limitations. This blind search for open clusters in the Galactic disc increases the number of known open clusters by 45%.

The role of asymptotic giant branch stars in the chemical evolution of the Galaxy

2018 ◽  
Vol 14 (S343) ◽  
pp. 510-511
Author(s):  
G. Tautvaišienė ◽  
C. Viscasillas Vázquez ◽  
V. Bagdonas ◽  
R. Smiljanic ◽  
A. Drazdauskas ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Capture ◽  
Open Clusters ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Galactic Disc ◽  
The Galaxy ◽  
Process Elements ◽  
Giant Branch Stars

AbstractAsymptotic giant branch stars play an important role in enriching galaxies by s-process elements. Recent studies have shown that their role in producing s-process elements in the Galactic disc was underestimated and should be reconsidered. Based on high-resolution spectra we have determined abundances of neutron-capture elements in a sample of 310 stars located in the field and open clusters and investigated elemental enrichment patterns according to their age and mean galactocentric distances.

scholarly journals Discovery and astrophysical properties of Galactic open clusters in dense stellar fields using Gaia DR2

2020 ◽  
Vol 496 (2) ◽  
pp. 2021-2038
Author(s):  
F A Ferreira ◽  
W J B Corradi ◽  
F F S Maia ◽  
M S Angelo ◽  
J F C Santos
Keyword(s):  
Milky Way ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Open Clusters ◽  
Galactic Latitude ◽  
Galactic Disc ◽  
New Findings ◽  
Low Latitudes ◽  
First Time ◽  
Gaia Dr2

ABSTRACT We report the discovery of 25 new open clusters resulting from a search in dense low Galactic latitude fields. We also provide, for the first time, structural and astrophysical parameters for the new findings and 34 other recently discovered open clusters using Gaia Data Release 2 (DR2) data. The candidates were confirmed by jointly inspecting the vector point diagrams and spatial distribution. The discoveries were validated by matching near known objects and comparing their mean astrometric parameters with the available literature. A decontamination algorithm was applied to the three-dimensional astrometric space to derive membership likelihoods for clusters stars. By rejecting stars with low membership likelihoods, we built decontaminated colour–magnitude diagrams and derived the clusters astrophysical parameters by isochrone fitting. The structural parameters were also derived by King-profile fittings over the stellar distributions. The investigated clusters are mainly located within 3 kpc from the Sun, with ages ranging from 30 Myr to 3.2 Gyr and reddening limited to E(B − V) = 2.5. On average, our cluster sample presents less concentrated structures than Gaia DR2 confirmed clusters, since the derived core radii are larger while the tidal radii are not significantly different. Most of them are located in the IV quadrant of the Galactic disc at low latitudes, therefore, they are immersed in dense fields characteristic of the inner Milky Way.

scholarly journals Search for the evolutionary relationship between Galactic globular and open clusters using data from the Gaia DR2 catalogue

2019 ◽  
Vol 488 (3) ◽  
pp. 3474-3481
Author(s):  
A T Bajkova ◽  
V V Bobylev
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Density Wave ◽  
Evolutionary Relationship ◽  
Open Clusters ◽  
Proper Motions ◽  
Galactic Disc ◽  
Disc Bulge ◽  
Using Data ◽  
Gaia Dr2

Abstract Passing through the Galactic disc, a massive object such as a globular cluster, can trigger star formation process leading to the birth of open clusters. Here, we analyse such possible evolutionary relationship between globular and open clusters. To search for the closest rapprochement between objects we computed backwards the orbits of 150 Galactic globular and 232 open clusters (younger than 100 Myr) with proper motions, derived from the Gaia DR2 catalogue. The orbits were computed using the recently modified three-component (disc, bulge, and halo) axisymmetric Navarro–Frenk–White potential, which was complemented by non-axisymmetric bar and spiral density wave potentials. We obtained a new estimate for the frequency of impacts of globular clusters about the Galactic disc, which is equal to four events for 1 Myr. In the framework of the considered scenario, we highlight the following nine pairs of globular and open clusters, with rapprochement within 1 kpc at the time of the intersection the Galactic disc by a globular cluster for the latest 100 Myr: NGC 104 – Turner 3, NGC 104 – NGC 6396, NGC 104 – Ruprecht 127, NGC 5139 – Trumpler 17, NGC 5139 – NGC 6520, NGC 6341 – NGC 6613, NGC 6838 – NGC 6520, NGC 7078 – NGC 7063, NGC 6760 – Ruprecht 127.

Sixteen Open Clusters Discovered with Sample-based Clustering Search of Gaia DR2

2020 ◽  
Vol 132 (1009) ◽  
pp. 034502 ◽  
Author(s):  
ChaoJie Hao ◽  
Ye Xu ◽  
ZhenYu Wu ◽  
ZhiHong He ◽  
ShuaiBo Bian
Keyword(s):  
Open Clusters ◽  
Clustering Search ◽  
Gaia Dr2

scholarly journals Extended main sequence turnoffs in open clusters as seen by Gaia – I. NGC 2818 and the role of stellar rotation

2018 ◽  
Vol 480 (3) ◽  
pp. 3739-3746 ◽  
Author(s):  
N Bastian ◽  
S Kamann ◽  
I Cabrera-Ziri ◽  
C Georgy ◽  
S Ekström ◽  
...  
Keyword(s):  
Main Sequence ◽  
Open Clusters ◽  
Stellar Rotation

scholarly journals Galaxy Dynamics: Secular Evolution and Accretion

2010 ◽  
Vol 6 (S271) ◽  
pp. 119-126 ◽  
Author(s):  
Francoise Combes
Keyword(s):  
Angular Momentum ◽  
Galaxy Evolution ◽  
Resonant Scattering ◽  
Relative Role ◽  
Radial Migration ◽  
Galaxy Dynamics ◽  
Secular Evolution ◽  
Minor Mergers ◽  
Gas Accretion

AbstractRecent results are reviewed on galaxy dynamics, bar evolution, destruction and re-formation, cold gas accretion, gas radial flows and AGN fueling, minor mergers. Some problems of galaxy evolution are discussed in particular, exchange of angular momentum, radial migration through resonant scattering, and consequences on abundance gradients, the frequency of bulgeless galaxies, and the relative role of secular evolution and hierarchical formation.

Yarkovsky drift detectability using the Gaia DR2 asteroid astrometry  

2021 ◽  
Author(s):  
Karolina Dziadura ◽  
Dagmara Oszkiewicz ◽  
Federika Spoto ◽  
Przemysław Bartczak
Keyword(s):  
Direct Detection ◽  
Signal To Noise Ratio ◽  
Parameter Determination ◽  
Small Bodies ◽  
Radar Observations ◽  
Orbital Parameters ◽  
Yarkovsky Effect ◽  
Reliable Detection ◽  
Right Ascension ◽  
Gaia Dr2

&lt;div&gt;The orbital motion of small bodies is affected by the Yarkovsky effect (semiminor axes change in time (da/dt)). The first direct detection was only made in 2003 thanks to radar observations. Nowadays there are over a hundred detections for NEAs and only a few for Main-Belt objects, however, the Yarkovsky effect remains difficult to detect for a large group of asteroids.&lt;/div&gt; &lt;div&gt;The ESA Gaia mission was claimed to provide extremely precise astrometry of asteroids. Gaia observations were expected to lead to new Yarkovsky detections. In this work, we present the results for the most promising Yarkovsky candidates indexed before the start of the mission.&lt;/div&gt; &lt;div&gt;We converted all available data (ground-based optical astrometry, satellite astrometry measurements, radar observations and GAIA DR2 data) to ADES format and then used it for orbit determination. We included the standard error of right ascension (RA), declination (Dec) and correlation of Ra and Dec errors for Gaia astrometry. We found a reliable detection of the Yarkovsky effect with a signal-to-noise ratio (SNR) greater than 3 for 21 asteroids, including 7 confirmations and 14 new detections. In 10 cases the resulting da/dt parameter SNR increased with the usage of the DR2 catalogue data, but no reliable detection can yet be claimed. Furthermore, we present a comparison of our empirical results with expected values estimated using physical and orbital parameters of studied objects. GAIA DR2 asteroids astrometry impacts positively the Yarkovsky drift determination. GAIA DR3 will elongate the observational arc, therefore, contribute to A2 parameter determination.&lt;/div&gt;

scholarly journals Characterising open clusters in the solar neighbourhood with the Tycho-Gaia Astrometric Solution

2018 ◽  
Vol 615 ◽  
pp. A49 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
A. Vallenari ◽  
R. Sordo ◽  
F. Pensabene ◽  
A. Krone-Martins ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
High Probability ◽  
Open Clusters ◽  
Distance Modulus ◽  
The Sun ◽  
Proper Motions ◽  
Orbital Parameters ◽  
Naval Observatory ◽  
Galactic Potential

Context. The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G ~ 12 mag. Aims. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or the fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4) proper motions, and TGAS parallaxes. Methods. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/Markov Chain Monte Carlo technique to fit stellar isochrones to the observed 2MASS JHKS magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. Results. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2 kpc, and cluster parameters from isochrone fitting for 26 of them located within a distance of 1 kpc from the Sun. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.

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