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.

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 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

scholarly journals Unbound Close Stellar Encounters in the Solar Neighborhood

2022 ◽  
Vol 163 (2) ◽  
pp. 44
Author(s):  
Bradley M. S. Hansen
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Radial Distance ◽  
Solar Neighborhood ◽  
Limiting Factors ◽  
Line Of Sight ◽  
The Sun ◽  
Finite Set ◽  
Host Stars ◽  
Migration Event

Abstract We present a catalog of unbound stellar pairs, within 100 pc of the Sun, that are undergoing close, hyperbolic, encounters. The data are drawn from the GAIA EDR3 catalog, and the limiting factors are errors in the radial distance and unknown velocities along the line of sight. Such stellar pairs have been suggested to be possible events associated with the migration of technological civilizations between stars. As such, this sample may represent a finite set of targets for a SETI search based on this hypothesis. Our catalog contains a total of 132 close passage events, featuring stars from across the entire main sequence, with 16 pairs featuring at least one main-sequence star of spectral type between K1 and F3. Many of these stars are also in binaries, so that we isolate eight single stars as the most likely candidates to search for an ongoing migration event—HD 87978, HD 92577, HD 50669, HD 44006, HD 80790, LSPM J2126+5338, LSPM J0646+1829 and HD 192486. Among host stars of known planets, the stars GJ 433 and HR 858 are the best candidates.

Local stellar distribution and galactic spiral structure

1970 ◽  
Vol 38 ◽  
pp. 189-198 ◽  
Author(s):  
S. W. McCuskey
Keyword(s):  
Spiral Structure ◽  
The Sun ◽  
Long Period ◽  
Classical Cepheids ◽  
Galactic Clusters ◽  
The Galaxy ◽  
Galactic Spiral Structure ◽  
Ob Associations ◽  
Galactic Spiral ◽  
Spiral Arm

Aside from the well-known spiral arm tracers such as the OB associations, young galactic clusters, WR stars and possibly the long-period classical cepheids, the more common stars in the neighborhood of the sun within 2 kpc show little or no relationship to the local spiral structure of the galaxy.

The nearby spiral density–wave structure of the Galaxy

2017 ◽  
Vol 468 (3) ◽  
pp. 3361-3367 ◽  
Author(s):  
Evgeny Griv ◽  
Ing-Guey Jiang ◽  
Li-Gang Hou
Keyword(s):  
Density Wave ◽  
Wave Structure ◽  
Spiral Density Wave ◽  
The Galaxy

scholarly journals Spiral structure of the Galaxy Derived from the Hat Creek survey of neutral hydrogen

1970 ◽  
Vol 38 ◽  
pp. 126-139 ◽  
Author(s):  
H. Weaver
Keyword(s):  
Pitch Angle ◽  
Spiral Structure ◽  
Neutral Hydrogen ◽  
The Sun ◽  
General Picture ◽  
Contour Maps ◽  
The Galaxy ◽  
External Galaxies ◽  
Perseus Arm ◽  
Spiral Arm

The extensive Hat Creek survey of neutral hydrogen combined with southern observations provides the basis for a new discussion of the spiral structure of the galaxy. The purpose of this investigation is to provide a general picture of the galaxy. It is found that the pitch of the spiral arms is approximately 12°.5 and that there are many spurs and interarm features as we observe in external galaxies.The sun is not located in a major spiral arm, but rather in a spur or offshoot originating near or at the Sagittarius arm, which is a major structure in the galaxy. The young stars in the general vicinity of the sun delineate this spur, not a major arm structure. The stars and the gas are in agreement in indicating a large pitch angle (20°–25°) for this local structure, which differs from the smaller pitch angle for the arms which form the system as a whole.In the presentation a computer-produced movie of the galaxy based on Hat Creek hydrogen contour maps similar to those in Figure 1 was shown. It was used to illustrate generally the complexity of the gas structure and, in particular, to show (i) observational aspects of the spur in which the sun is located and (ii) the point of origin of the so-called Perseus arm.

scholarly journals Density waves and the viscous overstability in Saturn’s rings

2019 ◽  
Vol 623 ◽  
pp. A121 ◽  
Author(s):  
M. Lehmann ◽  
J. Schmidt ◽  
H. Salo
Keyword(s):  
Large Scale ◽  
Density Wave ◽  
Relative Magnitude ◽  
Density Waves ◽  
Scale Free ◽  
Short Scale ◽  
Spiral Density Waves ◽  
Saturn’S Rings ◽  
Saturn's Rings ◽  
Lindblad Resonance

This paper considers resonantly forced spiral density waves in a dense planetary ring that is close to the threshold for viscous overstability. We solved numerically the hydrodynamical equations for a dense thin disk in the vicinity of an inner Lindblad resonance with a perturbing satellite. Our numerical scheme is one-dimensional so that the spiral shape of a density wave is taken into account through a suitable approximation of the advective terms arising from the fluid orbital motion. This paper is a first attempt to model the co-existence of resonantly forced density waves and short-scale free overstable wavetrains as observed in Saturn’s rings, by conducting large-scale hydrodynamical integrations. These integrations reveal that the two wave types undergo complex interactions, not taken into account in existing models for the damping of density waves. In particular we found that, depending on the relative magnitude of both wave types, the presence of viscous overstability can lead to the damping of an unstable density wave and vice versa. The damping of the short-scale viscous overstability by a density wave was investigated further by employing a simplified model of an axisymmetric ring perturbed by a nearby Lindblad resonance. A linear hydrodynamic stability analysis as well as local N-body simulations of this model system were performed and support the results of our large-scale hydrodynamical integrations.

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