A model for the Lin-Shu type density-wave structure of our Galaxy: Line-of-sight and transverse-longitudinal velocities of 242 optically visible open clusters

2015 ◽  
Vol 336 (2) ◽  
pp. 196-207 ◽  
Author(s):  
E. Griv ◽  
I.-G. Jiang
Keyword(s):  
Density Wave ◽  
Wave Structure ◽  
Open Clusters ◽  
Line Of Sight

The Lin–Shu type density–wave structure of the Galaxy: Line-of-sight velocities of selected 37354 RAVE DR5 stars

New Astronomy ◽  
2019 ◽  
Vol 66 ◽  
pp. 1-8 ◽  
Author(s):  
Evgeny Griv ◽  
Ing-Guey Jiang ◽  
Li-Gang Hou ◽  
Chow-Choong Ngeow
Keyword(s):  
Density Wave ◽  
Wave Structure ◽  
Line Of Sight ◽  
The Galaxy

The nearby spiral density-wave structure of the Galaxy: line-of-sight velocities of the Gaia DR2 OB stars

2021 ◽  
Vol 503 (1) ◽  
pp. 354-361
Author(s):  
Evgeny Griv ◽  
Michael Gedalin ◽  
Ing-Guey Jiang
Keyword(s):  
Density Wave ◽  
Wave Structure ◽  
Wave Theory ◽  
Solar Neighborhood ◽  
Line Of Sight ◽  
Density Waves ◽  
Ob Stars ◽  
Spiral Density Waves ◽  
The Galaxy ◽  
Gravity Disturbances

ABSTRACT Distances and line-of-sight velocities of 964 Gaia Data Release 2 (DR2) OB stars of Xu et al. within 3 kpc from the Sun and 500 pc from the Galactic mid-plane with accuracies of <50 per cent are selected. The data are used to find small systematic departures of velocities from the mean circular motion for the stars in the solar neighborhood due to the spiral compression-type (Lin–Shu-type) waves, or spiral density waves, e.g. those produced by real instabilities of spontaneous gravity disturbances, a central bar or a companion system. A key point of the study is that our results are consistent with the ones extracted from the asymptotic density-wave theory. Revised parameters of density waves in the solar vicinity of the Galaxy are also provided.

The nearby spiral density-wave structure of the Galaxy: line-of-sight velocities of the Gaia DR2 main-sequence A, F, G, and K stars

2020 ◽  
Vol 493 (2) ◽  
pp. 2111-2126
Author(s):  
Evgeny Griv ◽  
Michael Gedalin ◽  
I-Chun Shih ◽  
Li-Gang Hou ◽  
Ing-Guey Jiang
Keyword(s):  
Main Sequence ◽  
Density Wave ◽  
Wave Structure ◽  
Wave Pattern ◽  
Line Of Sight ◽  
The Sun ◽  
Density Waves ◽  
Spiral Density Waves ◽  
The Galaxy ◽  
Spiral Arm

ABSTRACT Distances and velocities of $\approx \!2400\, 000$ main-sequence A, F, G, and K stars are collected from the second data release of ESA's Gaia astrometric mission. This material is analysed to find evidence of radial and azimuthal systematic non-circular motions of stars in the solar neighbourhood on the assumption that the system is subject to spiral density waves (those produced by a spontaneous disturbance, a central bar, or an external companion), developing in the Galactic disc. Data analysis of line-of-sight velocities of $\approx \!1500\, 000$ stars selected within 2 kpc from the Sun and 500 pc from the Galactic mid-plane with distance accuracies of <10 per cent makes evident that a radial wavelength of the wave pattern is 1.1–1.6 kpc and a phase of the wave at the Sun’s location in the Galaxy is 55°–95°. Respectively, the Sun is situated at the inner edge of the nearest Orion spiral arm segment. Thus, the local Orion arm is a part of a predominant density-wave structure of the system. The spiral structure of the Galaxy has an oscillating nature corresponding to a concept of the Lin–Shu-type moderately growing in amplitude, tightly wound, and rigidly rotating density waves.

scholarly journals Collinder 135 and UBC 7: A physical pair of open clusters

2020 ◽  
Vol 642 ◽  
pp. L4
Author(s):  
Dana A. Kovaleva ◽  
Marina Ishchenko ◽  
Ekaterina Postnikova ◽  
Peter Berczik ◽  
Anatoly E. Piskunov ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Observational Evidence ◽  
Open Clusters ◽  
Line Of Sight ◽  
Kinematic Parameters ◽  
Current Line ◽  
Chance Coincidence ◽  
The Past ◽  
Link Type ◽  
Spatial Coordinates

Context. Given the closeness of the two open clusters Collinder 135 and UBC 7 on the sky, we investigate the possibility that the two clusters are physically related. Aims. We aim to recover the present-day stellar membership in the open clusters Cr 135 and UBC 7 (300 pc from the Sun) in order to constrain their kinematic parameters, ages, and masses and to restore their primordial phase space configuration. Methods. The most reliable cluster members are selected with our traditional method modified for the use of Gaia DR2 data. Numerical simulations use the integration of cluster trajectories backwards in time with our original high-order Hermite4 code φ−GRAPE. Results. We constrain the age, spatial coordinates, velocities, radii, and masses of the clusters. We estimate the actual separation of the cluster centres equal to 24 pc. The orbital integration shows that the clusters were much closer in the past if their current line-of-sight velocities are very similar and the total mass is more than seven times larger than the mass of the most reliable members. Conclusions. We conclude that the two clusters Cr 135 and UBC 7 might very well have formed a physical pair based on the observational evidence as well as numerical simulations. The probability of a chance coincidence is only about 2%.

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