scholarly journals The Distribution of Open Clusters in the Galaxy

2021 ◽  
Vol 8 ◽  
Author(s):  
Hektor Monteiro ◽  
Douglas A. Barros ◽  
Wilton S. Dias ◽  
Jacques R. D. Lépine
Keyword(s):  
Galactic Plane ◽  
Rotation Velocity ◽  
Open Clusters ◽  
Space Distribution ◽  
Proper Motions ◽  
Corotation Radius ◽  
The Galaxy ◽  
Galactic Abundance ◽  
Galactic Orbit ◽  
Gaia Dr2

In this work we explore the new catalog of galactic open clusters that became available recently, containing 1,750 clusters that have been re-analyzed using the Gaia DR2 catalog to determine the stellar memberships. We used the young open clusters as tracers of spiral arms and determined the spiral pattern rotation speed of the Galaxy and the corotation radius, the strongest Galactic resonance. The sample of open clusters used here is increased by dozens of objects with respect to our previous works. In addition, the distances and ages values are better determined, using improvements to isochrone fitting and including an updated extinction polynomial for the Gaia DR2 photometric band-passes, and the Galactic abundance gradient as a prior for metallicity. In addition to the better age determinations, the catalog contains better positions in the Galactic plane and better proper motions. This allow us to discuss not only the present space distribution of the clusters, but also the space distribution of the clusters's birthplaces, obtained by integration of the orbits for a time equal to their age. The value of the rotation velocity of the arms (28.5 ± 1.0 km s−1 kpc−1) implies that the corotation radius (Rc) is close to the solar Galactic orbit (Rc/R0 = 1.01±0.08), which is supported by other observational evidence discussed in this text. A simulation is presented, illustrating the motion of the clusters in the reference frame of corotation. We also present general statistics of the catalog of clusters, like spatial distribution, distribution relative to height from the Galactic plane, and distribution of ages and metallicity. An important feature of the space distribution, the corotation gap in the gas distribution and its consequences for the young clusters, is discussed.

scholarly journals The tale of the Milky Way globular cluster NGC 6362 – I. The orbit and its possible extended star debris features as revealed by Gaia DR2

2019 ◽  
Vol 489 (4) ◽  
pp. 4565-4573
Author(s):  
Richa Kundu ◽  
José G Fernández-Trincado ◽  
Dante Minniti ◽  
Harinder P Singh ◽  
Edmundo Moreno ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Vertical Component ◽  
Galactic Disc ◽  
Corotation Radius ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
History Of ◽  
Event Based ◽  
Gaia Dr2

ABSTRACTWe report the identification of possible extended star debris candidates beyond the cluster tidal radius of NGC 6362 based on the second Gaia data release (Gaia DR2). We found 259 objects possibly associated with the cluster lying in the vicinity of the giant branch and 1–2 magnitudes fainter/brighter than the main-sequence turn-off in the cluster colour–magnitude diagram and which cover an area on the sky of ∼4.1 deg2 centred on the cluster. We traced back the orbit of NGC 6362 in a realistic Milky Way potential, using the gravpot16 package, for 3 Gyr. The orbit shows that the cluster shares similar orbital properties as the inner disc, having peri-/apogalactic distances, and maximum vertical excursion from the Galactic plane inside the corotation radius (CR), moving inwards from CR radius to visit the inner regions of the Milky Way. The dynamical history of the cluster reveals that it has crossed the Galactic disc several times in its lifetime and has recently undergone a gravitational shock, ∼15.9 Myr ago, suggesting that less than 0.1 per cent of its mass has been lost during the current disc-shocking event. Based on the cluster’s orbit and position in the Galaxy, we conclude that the possible extended star debris candidates are a combined effect of the shocks from the Galactic disc and evaporation from the cluster. Lastly, the evolution of the vertical component of the angular momentum shows that the cluster is strongly affected dynamically by the Galactic bar potential.

scholarly journals Fundamental parameters for 45 open clusters with Gaia DR2, an improved extinction correction and a metallicity gradient prior

2020 ◽  
Vol 499 (2) ◽  
pp. 1874-1889
Author(s):  
H Monteiro ◽  
W S Dias ◽  
A Moitinho ◽  
T Cantat-Gaudin ◽  
J R D Lépine ◽  
...  
Keyword(s):  
Maximum Likelihood Method ◽  
Interstellar Extinction ◽  
Substantial Improvement ◽  
Open Clusters ◽  
Likelihood Method ◽  
Proper Motions ◽  
Review Of The Literature ◽  
Fundamental Parameters ◽  
Galactic Abundance ◽  
Gaia Dr2

ABSTRACT Reliable fundamental parameters of open clusters (OCs) such as distance, age, and extinction are key to our understanding of Galactic structure and stellar evolution. In this work, we use Gaia Data Release 2 (DR2) to investigate 45 OCs listed in the New catalogue of optically visible open clusters and candidates (DAML) but with no previous astrometric membership estimation based on Gaia DR2. In the process of selecting targets for this study, we found that some clusters reported as new discoveries in recent papers based on Gaia DR2 were already known clusters listed in DAML. Cluster memberships were determined using a maximum likelihood method applied to Gaia DR2 astrometry. This has allowed us to estimate mean proper motions and mean parallaxes for all investigated clusters. Mean radial velocities were also determined for 12 clusters, 7 of which had no previous published values. We have improved our isochrone fitting code to account for interstellar extinction using an updated extinction polynomial for the Gaia DR2 photometric bandpasses and the Galactic abundance gradient as a prior for metallicity. The updated procedure was validated with a sample of clusters with high-quality [Fe/H] determinations. We then did a critical review of the literature and verified that our cluster parameter determinations represent a substantial improvement over previous values.

scholarly journals Analysis of galaxy kinematics based on Cepheids from the Gaia DR2 Catalogue

2021 ◽  
Vol 502 (3) ◽  
pp. 4377-4391
Author(s):  
V V Bobylev ◽  
A T Bajkova ◽  
A S Rastorguev ◽  
M V Zabolotskikh
Keyword(s):  
Density Wave ◽  
Rotation Velocity ◽  
Proper Motions ◽  
The Past ◽  
Spiral Density Wave ◽  
Classical Cepheids ◽  
The Galaxy ◽  
Galaxy Kinematics ◽  
The One ◽  
Gaia Dr2

ABSTRACT To construct the rotation curve of the Galaxy, classical Cepheids with proper motions, parallaxes and line-of-sight velocities from the Gaia DR2 Catalogue are used in large part. Our working sample formed from literature data contains about 800 Cepheids with estimates of their age. We determined that the linear rotation velocity of the Galaxy at the solar distance is V0 = 240 ± 3 km s−1. In this case, the distance from the Sun to the axis of rotation of the Galaxy is found to be R0 = 8.27 ± 0.10 kpc. A spectral analysis of radial and residual tangential velocities of Cepheids younger than 120 Myr showed close estimates of the parameters of the spiral density wave obtained from data both at the present time and in the past. Therefore, the value of the wavelength λR, θ is in the range [2.4–3.0] kpc, the pitch angle iR, θ is in the range [−13○, −10○] for a four-arm pattern model, and the amplitudes of the radial and tangential perturbations are fR ∼ 12 km s−1 and fθ ∼ 9 km s−1, respectively. Velocities of Cepheids older than 120 Myr currently give a wavelength λR, θ ∼ 5 kpc. This value differs significantly from the one we obtained from samples of young Cepheids. An analysis of the positions and velocities of old Cepheids, calculated by integrating their orbits backward in time, made it possible to determine significantly more reliable values of the parameters of the spiral density wave: wavelength λR, θ = 2.7 kpc and amplitudes of radial and tangential perturbations fR = 7.9 km s−1 and fθ = 5 km s−1, respectively.

scholarly journals A Gaia DR2 view of the open cluster population in the Milky Way

2018 ◽  
Vol 618 ◽  
pp. A93 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
C. Jordi ◽  
A. Vallenari ◽  
A. Bragaglia ◽  
L. Balaguer-Núñez ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Open Cluster ◽  
Open Clusters ◽  
Number Of Clusters ◽  
History Of ◽  
Gaia Dr2

Context. Open clusters are convenient probes of the structure and history of the Galactic disk. They are also fundamental to stellar evolution studies. The second Gaia data release contains precise astrometry at the submilliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. Aims. In this study we aim to establish a list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. Methods. We compiled a list of thousands of known or putative clusters from the literature. We then applied an unsupervised membership assignment code, UPMASK, to the Gaia DR2 data contained within the fields of those clusters. Results. We obtained a list of members and cluster parameters for 1229 clusters. As expected, the youngest clusters are seen to be tightly distributed near the Galactic plane and to trace the spiral arms of the Milky Way, while older objects are more uniformly distributed, deviate further from the plane, and tend to be located at larger Galactocentric distances. Thanks to the quality of Gaia DR2 astrometry, the fully homogeneous parameters derived in this study are the most precise to date. Furthermore, we report on the serendipitous discovery of 60 new open clusters in the fields analysed during this study.

scholarly journals Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm

2019 ◽  
Vol 488 (2) ◽  
pp. 1635-1651 ◽  
Author(s):  
M S Angelo ◽  
A E Piatti ◽  
W S Dias ◽  
F F S Maia
Keyword(s):  
Structural Parameters ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Mass Star ◽  
Proper Motions ◽  
Concentration Parameter ◽  
Low Mass ◽  
Gaia Dr2 ◽  
Spiral Arm

Abstract The study of dynamical properties of Galactic open clusters (OCs) is a fundamental prerequisite for the comprehension of their dissolution processes. In this work, we characterized 12 OCs, namely: Collinder 258, NGC 6756, Czernik 37, NGC 5381, Ruprecht 111, Ruprecht 102, NGC 6249, Basel 5, Ruprecht 97, Trumpler 25, ESO 129−SC32, and BH 150, projected against dense stellar fields. In order to do that, we employed Washington CT1 photometry and Gaia DR2 astrometry, combined with a decontamination algorithm applied to the three-dimensional astrometric space of proper motions and parallaxes. From the derived membership likelihoods, we built decontaminated colour–magnitude diagrams, while structural parameters were obtained from King profiles fitting. Our analysis revealed that they are relatively young OCs (log(t  yr−1) ∼7.3–8.6), placed along the Sagittarius spiral arm, and at different internal dynamical stages. We found that the half-light radius to Jacobi radius ratio, the concentration parameter and the age to relaxation time ratio describe satisfactorily their different stages of dynamical evolution. Those relative more dynamically evolved OCs have apparently experienced more important low-mass star loss.

scholarly journals An Overview of the Globular Cluster System of the Galaxy

1988 ◽  
Vol 126 ◽  
pp. 37-48
Author(s):  
Robert Zinn
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
Cluster System ◽  
Open Clusters ◽  
The Galaxy ◽  
Globular Cluster System ◽  
Harlow Shapley

Harlow Shapley (1918) used the positions of globular clusters in space to determine the dimensions of our Galaxy. His conclusion that the Sun does not lie near the center of the Galaxy is widely recognized as one of the most important astronomical discoveries of this century. Nearly as important, but much less publicized, was his realization that, unlike stars, open clusters, HII regions and planetary nebulae, globular clusters are not concentrated near the plane of the Milky Way. His data showed that the globular clusters are distributed over very large distances from the galactic plane and the galactic center. Ever since this discovery that the Galaxy has a vast halo containing globular clusters, it has been clear that these clusters are key objects for probing the evolution of the Galaxy. Later work, which showed that globular clusters are very old and, on average, very metal poor, underscored their importance. In the spirit of this research, which started with Shapley's, this review discusses the characteristics of the globular cluster system that have the most bearing on the evolution of the Galaxy.

scholarly journals Spatial distribution of exoplanet candidates based on Kepler and Gaia data

2020 ◽  
Vol 635 ◽  
pp. A191
Author(s):  
A. Maliuk ◽  
J. Budaj
Keyword(s):  
Spatial Distribution ◽  
Galactic Plane ◽  
Open Clusters ◽  
Field Of View ◽  
Solar Neighbourhood ◽  
Spatial Gradients ◽  
The Galaxy ◽  
Formation And Evolution ◽  
F Stars ◽  
Galactic Longitude

Context. Surveying the spatial distribution of exoplanets in the Galaxy is important for improving our understanding of planet formation and evolution. Aims. We aim to determine the spatial gradients of exoplanet occurrence in the Solar neighbourhood and in the vicinity of open clusters. Methods. We combined Kepler and Gaia DR2 data for this purpose, splitting the volume sampled by the Kepler mission into certain spatial bins. We determined an uncorrected and bias-corrected exoplanet frequency and metallicity for each bin. Results. There is a clear drop in the uncorrected exoplanet frequency with distance for F-type stars (mainly for smaller planets), a decline with increasing distance along the Galactic longitude l = 90°, and a drop with height above the Galactic plane. We find that the metallicity behaviour cannot be the reason for the drop of the exoplanet frequency around F stars with increasing distance. This might have only contributed to the drop in uncorrected exoplanet frequency with the height above the Galactic plane. We argue that the above-mentioned gradients of uncorrected exoplanet frequency are a manifestation of a single bias of undetected smaller planets around fainter stars. When we correct for observational biases, most of these gradients in exoplanet frequency become statistically insignificant. Only a slight decline of the planet occurrence with distance for F stars remains significant at the 3σ level. Apart from that, the spatial distribution of exoplanets in the Kepler field of view is compatible with a homogeneous one. At the same time, we do not find a significant change in the exoplanet frequency with increasing distance from open clusters. In terms of byproducts, we identified six exoplanet host star candidates that are members of open clusters. Four of them are in the NGC 6811 (KIC 9655005, KIC 9533489, Kepler-66, Kepler-67) and two belong to NGC 6866 (KIC 8396288, KIC 8331612). Two out of the six had already been known to be cluster members.

scholarly journals Probing the structure of the Galactic disk through open clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 482-482
Author(s):  
Xiaoying Pang ◽  
Chenggang Shu
Keyword(s):  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Age Distribution ◽  
Outer Part ◽  
Simulation Models ◽  
Open Clusters ◽  
Galactocentric Distance ◽  
Distance Measurements ◽  
The Galaxy

AbstractThe WEBDA database of open clusters (hereafter OCs) in the Galaxy contains 970 OCs, of which 911 have age determinations, 920 have distance measurements, and 911 have color-excess data. Base on the statistical analysis of global properties of open clusters, we investigate disk properties such as the height above the Galactic plane. We find that old open clusters (age ≥ 1 Gyr) are preferentially located far from the Galactic plane with 〈|z|〉~394.5 pc. They lie in the outer part of the Galactic disk. The young open clusters are distributed in the Galactic plane almost symmetrically with respect to the Sun, with a scale height perpendicular to the Galactic plane of 50.5 pc. The age distribution of open clusters can be fit approximately with a two-component exponential decay function: one component has an age scale factor of 225.2 Myr, and the other consists of longer-lived clusters with an age scale of 1.8 Gyr, which are smaller than those derived by Janes & Phelps (1994) of 200 Myr and 4 Gyr for the young and old OCs, respectively. As a consequence of completeness effects, the observed radial distribution of OCs with respect to Galactocentric distance does not follow the expected exponential profile. Instead, it falls off both for regions external to the solar circle and more sharply towards the Galactic Center, which is probably due to giant molecular cloud disruption in the center. We simulate the effects of completeness, assuming that the observed distribution of the number of OCs with a given number of stars above the background is representative of the intrinsic distribution of OCs throughout the Galaxy. Two simulation models are considered, in which the intrinsic number of the observable stars are distributed (i) assuming the actual positions of the OCs in the sample, and (ii) random selection of OC positions. As a result, we derive completeness-corrected radial distributions which agree with an exponential disk throughout the observed Galactocentric distance in the range of 5–15 kpc, with scale lengths in the range of 1.6–2.8 kpc.

scholarly journals The Outer Ring of the Galaxy Revealed by Young Open Clusters

2016 ◽  
Vol 25 (1) ◽  
Author(s):  
A. M. Mel’nik ◽  
P. Rautiainen ◽  
E. V. Glushkova ◽  
A. K. Dambis
Keyword(s):  
Galactic Plane ◽  
Open Clusters ◽  
Outer Ring ◽  
The Galaxy

AbstractThe distribution of young open clusters in the Galactic plane suggests the existence of the outer ring

Investigation of the nearby open clusters with Gaia DR2 data

2019 ◽  
Vol 14 (S351) ◽  
pp. 502-506
Author(s):  
Anton F. Seleznev ◽  
Vladimir M. Danilov ◽  
Giovanni Carraro
Keyword(s):  
Three Dimensional ◽  
Open Clusters ◽  
Dimensional Structure ◽  
Proper Motions ◽  
Membership Probability ◽  
First Results ◽  
Alpha Persei ◽  
Mass Functions ◽  
Tidal Tails ◽  
Gaia Dr2

AbstractGaia DR2 catalog provides a unique possibility to study the three-dimensional structure and the three-dimensional velocity field of the nearby open clusters. We can either select stars with a maximum membership probability and the most accurate values for the proper motions, parallaxes, and the radial velocities, or study these clusters statistically using overwhelmingly large areas of sky of tens by tens degrees. The second approach allows us to reveal the extensive outer parts of the clusters - a corona and the tidal tails and to study the luminosity and mass functions of these clusters. We present the first results of the investigation of several nearby open clusters, including Pleiades, Alpha Persei, Ruprecht 147.

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