scholarly journals Birth sites of young stellar associations and recent star formation in a flocculent corrugated disc

2020 ◽  
Vol 499 (4) ◽  
pp. 5623-5640
Author(s):  
Alice C Quillen ◽  
Alex R Pettitt ◽  
Sukanya Chakrabarti ◽  
Yifan Zhang ◽  
Jonathan Gagné ◽  
...  
Keyword(s):  
Space Distribution ◽  
Solar Neighbourhood ◽  
Low Velocity ◽  
Stellar Association ◽  
Stellar Orbits ◽  
Pattern Speeds ◽  
Moving Groups ◽  
Orbit Integration ◽  
Stellar Associations ◽  
Spiral Arm

ABSTRACT With backwards orbit integration, we estimate birth locations of young stellar associations and moving groups identified in the solar neighbourhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at a smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun’s galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a filamentary and corrugated disc of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighbourhood. This would be expected if they were born in a spiral arm, which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low-velocity dispersion disc stars.

scholarly journals Connecting Moving Groups to the Bar and Spiral Arms of the Milky Way

2009 ◽  
Vol 5 (H15) ◽  
pp. 192-192
Author(s):  
T. Antoja ◽  
O. Valenzuela ◽  
F. Figueras ◽  
B. Pichardo ◽  
E. Moreno
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Velocity Distribution ◽  
Test Particle ◽  
Milky Way ◽  
Solar Neighbourhood ◽  
Spiral Arms ◽  
Particle Orbit ◽  
Moving Groups ◽  
Orbit Integration

AbstractWe use test-particle orbit integration with a realistic Milky Way (MW) potential to study the effect of the resonances of the Galactic bar and spiral arms on the velocity distribution of the Solar Neighbourhood and other positions of the disk. Our results show that spiral arms create abundant kinematic substructure and crowd stars into the region of the Hercules moving group in the velocity plane. Bar resonances can contribute to the origin of low-angular momentum moving groups like Arcturus. Particles in the predicted dark disk of the MW should be affected by the same resonances as stars, triggering dark-matter moving groups in the disk. Finally, we evaluate how this study will be advanced by upcoming Gaia data.

scholarly journals Dynamics of the Spiral-Arm Corotation and Its Observable Footprints in the Solar Neighborhood

2021 ◽  
Vol 8 ◽  
Author(s):  
Douglas A. Barros ◽  
Angeles Pérez-Villegas ◽  
Tatiana A. Michtchenko ◽  
Jacques R. D. Lépine
Keyword(s):  
Galactic Disk ◽  
Stellar Dynamics ◽  
Solar Neighborhood ◽  
The Sun ◽  
Chaotic Motions ◽  
Phase Mixing ◽  
Stellar Orbits ◽  
Moving Groups ◽  
Life On Earth ◽  
Spiral Arm

This article discusses the effects of the spiral-arm corotation on the stellar dynamics in the Solar Neighborhood (SN). All our results presented here rely on: (1) observational evidence that the Sun lies near the corotation circle, where stars rotate with the same angular velocity as the spiral-arm pattern; the corotation circle establishes domains of the corotation resonance (CR) in the Galactic disk; (2) dynamical constraints that put the spiral-arm potential as the dominant perturbation in the SN, comparing with the effects of the central bar in the SN; (3) a long-lived nature of the spiral structure, promoting a state of dynamical relaxing and phase-mixing of the stellar orbits in response to the spiral perturbation. With an analytical model for the Galactic potential, composed of an axisymmetric background deduced from the observed rotation curve, and perturbed by a four-armed spiral pattern, numerical simulations of stellar orbits are performed to delineate the domains of regular and chaotic motions shaped by the resonances. Such studies show that stars can be trapped inside the stable zones of the spiral CR, and this orbital trapping mechanism could explain the dynamical origin of the Local arm of the Milky Way (MW). The spiral CR and the near high-order epicyclic resonances influence the velocity distribution in the SN, creating the observable structures such as moving groups and their radially extended counterpart known as diagonal ridges. The Sun and most of the SN stars evolve inside a stable zone of the spiral CR, never crossing the main spiral-arm structure, but oscillating in the region between the Sagittarius-Carina and Perseus arms. This orbital behavior of the Sun brings insights to our understanding of questions concerning the solar system evolution, the Earth environment changes, and the preservation of life on Earth.

scholarly journals A kinematically hot population of young stars in the solar neighbourhood

2020 ◽  
Vol 494 (2) ◽  
pp. 2429-2439 ◽  
Author(s):  
A S Binks ◽  
R D Jeffries ◽  
N J Wright
Keyword(s):  
Young Stars ◽  
Solar Neighbourhood ◽  
Mass Distributions ◽  
Systematic Effort ◽  
Low Mass ◽  
Moving Groups

ABSTRACT In the last three decades several hundred nearby members of young stellar moving groups (MGs) have been identified, but there has been less systematic effort to quantify or characterize young stars that do not belong to previously identified MGs. Using a kinematically unbiased sample of 225 lithium-rich stars within 100 pc, we find that only 50 ± 10 per cent of young (≲125 Myr), low-mass (0.5 < M/M⊙ < 1.0) stars, are kinematically associated with known MGs. Whilst we find some evidence that five of the non-MG stars may be connected with the Lower Centaurus–Crux association, the rest form a kinematically ‘hotter’ population, much more broadly dispersed in velocity, and with no obvious concentrations in space. The mass distributions of the MG members and non-MG stars are similar, but the non-MG stars may be older on average. We briefly discuss several explanations for the origin of the non-MG population.

Exploring the Origin of Moving Groups and Diagonal Ridges by Simulations of Stellar Orbits and Birthplaces

2020 ◽  
Vol 888 (2) ◽  
pp. 75 ◽  
Author(s):  
Douglas A. Barros ◽  
Angeles Pérez-Villegas ◽  
Jacques R. D. Lépine ◽  
Tatiana A. Michtchenko ◽  
Ronaldo S. S. Vieira
Keyword(s):  
Stellar Orbits ◽  
Moving Groups

scholarly journals Not gone with the wind: Planet occurrence is independent of stellar galactocentric velocity

2019 ◽  
Vol 489 (2) ◽  
pp. 2505-2510 ◽  
Author(s):  
Moiya A S McTier ◽  
David M Kipping
Keyword(s):  
Solar Neighbourhood ◽  
P Value ◽  
Selection Function ◽  
Strong Correlations ◽  
Velocity Data ◽  
Low Velocity ◽  
Gone With The Wind ◽  
Host Stars ◽  
Radial Velocity Data ◽  
Gaia Dr2

Abstract We demonstrate that planet occurrence does not depend on stellar galactocentric velocity in the Solar neighbourhood. Using Gaia DR2 astrometry and radial velocity data, we calculate 3D galactocentric velocities for 197 090 Kepler field stars, 1647 of which are confirmed planet hosts. When we compare the galactocentric velocities of planet hosts to those of the entire field star sample, we observe a statistically significant (KS p-value  = 10−70) distinction, with planet hosts being apparently slower than field stars by ∼40 km s−1. We explore some potential explanations for this difference and conclude that it is not a consequence of the planet–metallicity relation or distinctions in the samples’ thin/thick disc membership, but rather an artefact of Kepler’s selection function. Non Kepler-host stars that have nearly identical distances, temperatures, surface gravities, and Kepler magnitudes to the confirmed planet hosts also have nearly identical velocity distributions. Using one of these identical non-host samples, we consider that the probability of a star with velocity vtot hosting a planet can be described by an exponential function proportional to $e^{(-v_{\mathrm{tot}}/v_0)}$. Using a Markov Chain Monte Carlo sampler, we determine that v0 >976 km s−1 to 99 per cent confidence, which implies that planets in the Solar neighbourhood are just as likely to form around high-velocity stars as they are around low-velocity stars. Our work highlights the subtle ways in which selection biases can create strong correlations without physical underpinnings.

scholarly journals The Red Dwarf Star Population in the Galaxy

1995 ◽  
Vol 151 ◽  
pp. 55-56 ◽  
Author(s):  
L.V. Mirzoyan
Keyword(s):  
Star Clusters ◽  
Space Distribution ◽  
Dwarf Star ◽  
Star Clusters And Associations ◽  
Dwarf Stars ◽  
The Galaxy ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
T Tau ◽  
Stellar Associations

Red dwarf stars in the Galaxy occur in three forms: as flare stars, T Tau stars and red dwarf stars of constant brightness. Haro (1957) suggested that all these stars present regular evolutionary stages of red dwarf stars.The space distribution of UV Cet flare stars in the solar vicinity indicates that these low luminosity stars belong to the disk population of the Galaxy. Therefore one can suppose that all red dwarf stars have a space distribution which is similar to that of the flare stars (Mirzoyan et al. 1988a). Only a small part of them is found in star clusters and associations. The T Tau stars are an exception: because of their very short lifetime, all of them are found in stellar associations.The space distribution of red dwarf stars is determined by the fact that all of them are formed in star clusters and associations and are finally lost from their stellar systems and merge into the general galactic field (Mirzoyan 1995).

scholarly journals Gravitational Bar and Spiral Arm Torques fromKs-band Observations and Implications for the Pattern Speeds

2004 ◽  
Vol 128 (1) ◽  
pp. 183-201 ◽  
Author(s):  
D. L. Block ◽  
R. Buta ◽  
J. H. Knapen ◽  
D. M. Elmegreen ◽  
B. G. Elmegreen ◽  
...  
Keyword(s):  
Pattern Speeds ◽  
Spiral Arm

scholarly journals Cloud-Particle Dynamics and Star Formation in Spiral Galaxies

1983 ◽  
Vol 100 ◽  
pp. 131-132
Author(s):  
W. W. Roberts ◽  
M. A. Hausman ◽  
F. H. Levinson
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Particle Dynamics ◽  
Particle Model ◽  
Computational Simulations ◽  
Physical Processes ◽  
Cloud Particle ◽  
Stellar Association ◽  
New Associations ◽  
Stellar Associations

We study the gas in a spiral galaxy with a cloud-dominated “stellar association-perturbed” interstellar medium from the standpoint of a cloud-particle model. Through N-body computational simulations, we follow the time evolution of the system of gas clouds and the corresponding system of young stellar associations forming from the clouds. Basic physical processes are modeled in a three-step cyclic procedure: (1) dynamical propagation of the clouds and young stellar associations, (2) simulation of cloud-cloud collisions, and (3) formation of new associations of protostars that are triggered by the local mechanisms of cloud-cloud collisions and cloud interactions with existing young stellar associations.

What we learn from TGAS about the moving groups of the Solar neighbourhood

2017 ◽  
Vol 12 (S330) ◽  
pp. 214-215
Author(s):  
B. Goldman ◽  
E. Schilbach ◽  
S. Röser ◽  
P. Schöfer ◽  
A. Derekas ◽  
...  
Keyword(s):  
Current Data ◽  
Radial Velocities ◽  
Common Origin ◽  
Solar Neighbourhood ◽  
Proper Motions ◽  
Moving Groups ◽  
The Individual

AbstractWe use the TGAS proper motions and parallaxes as well as published and new radial velocities to study the dynamics of nearby moving groups. In particular we try to determine their age using backtracing of the individual members to a common origin. We find that the current data, probably the radial velocities, do not allow to reach a successful conclusion.

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