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 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.

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 Distribution and motions of HI in M31

1985 ◽  
Vol 106 ◽  
pp. 437-442
Author(s):  
E. Brinks ◽  
W. B. Burton
Keyword(s):  
High Resolution ◽  
Atomic Hydrogen ◽  
Line Of Sight ◽  
Complete Model ◽  
Previous Survey ◽  
The Past ◽  
The Galaxy ◽  
The One

It has become clear in the past few years that the distribution and kinematics of HI in M31 is far from simple. The new high-resolution survey made with the Westerbork SRT in the 21-cm line of atomic hydrogen by Brinks and Shane (1983) shows this dramatically. Along almost any line of sight through M31 two separate velocity systems are sampled. Based on a previous survey Shane (1978) and later Bajaja and Shane (1982) proposed that the extra component is due to warping of the plane of the galaxy into the direction of and crossing the line-of-sight. Roberts et al. (1978) and Whitehurst et al. (1978) emphasized that the observed profile structure ruled out confinement of the gas to a thin plane. Unwin (1983) reached a similar conclusion on the basis of his survey. The most complete model produced up until now which accounts for the two velocity systems is the one by Henderson (1979), based on the 100-m Effelsberg survey of M31 by Cram et al. (1980)

Extra-tidal features using Gaia DR2

2019 ◽  
Vol 14 (S351) ◽  
pp. 420-421
Author(s):  
Julio A. Carballo-Bello
Keyword(s):  
Mass Distribution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Space Mission ◽  
Cluster Center ◽  
Proper Motions ◽  
The Galaxy ◽  
Tidal Tails ◽  
Gaia Dr2

AbstractIn recent years, we have gathered enough evidence showing that most of the Galactic globular clusters extend well beyond their King tidal radii and fill their Jacobi radii in the form of “extended stellar haloes”. In some cases, because of the interaction with the Milky Way, stars are able to exceed the Jacobi radius, generating tidal tails which may be used to trace the mass distribution in the Galaxy. In this work, we use the precious information provided by the space mission Gaia (photometry, parallaxes and proper motions) to analyze NGC 362 in the search for member stars in its surroundings. Our preliminar results suggest that it is possible to identify member stars and tidal features up to distances of a few degrees from the globular cluster center.

scholarly journals Identifying birth places of high-velocity stars

2018 ◽  
pp. 211-222
Author(s):  
V. Hambaryan ◽  
R. Neuh¨auser
Keyword(s):  
Monte Carlo ◽  
Neutron Star ◽  
High Velocity ◽  
Covariance Matrices ◽  
High Quality ◽  
Stellar Cluster ◽  
The Past ◽  
The Galaxy ◽  
Astrometric Data ◽  
Gaia Dr2

We searched for the high-velocity and isolated neutron stars that encountered in the past with a stellar cluster/association closer than 20 pc. We took about 830000 stars with the high-quality astrometry and radial velocities from the Gaia DR2 catalogue and empirically selected about 560 high-velocity stars. We used a full gravitational potential of the Galaxy to calculate the motion of a stellar cluster/association and a candidate of high-velocity star from their current positions to the proximity epoch. For these calculations we used a numerical integration in rectangular, Galactocentric coordinates. We used a covariance matrices of the astrometric data for each star to estimate the accuracy of the obtained proximity distance and epoch. For this aim we used a Monte Carlo method, replaced each star with 10 000 of its simulations and studied the distribution of their individual close passages near a stellar cluster/association. In addition, we investigated a neutron star/runaway star pairs very likely both ejected from binary system during supernova event.

scholarly journals Mass distribution of the Galaxy with VERA

2012 ◽  
Vol 8 (S287) ◽  
pp. 421-422
Author(s):  
Nobuyuki Sakai ◽  
Mareki Honma ◽  
Hiroyuki Nakanishi ◽  
Hirofumi Sakanoue ◽  
Tomoharu Kurayama ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Rotation Curve ◽  
Galactic Center ◽  
Rotation Velocity ◽  
Galactic Rotation ◽  
Proper Motions ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Peculiar Motion ◽  
Perseus Arm

AbstractWe aim to reveal the mass distribution of the Galaxy based on a precise rotation curve constructed using VERA observations. We have been observing Galactic H2O masers with VERA. We here report one of the results of VERA for IRAS 05168+3634. The parallax is 0.532 ± 0.053 mas which corresponds to a distance of 1.88+0.21−0.17 kpc, and the proper motions are (μαcosδ, μδ) = (0.23 ± 1.07, −3.14 ± 0.28) mas yr−1. The distance is significantly smaller than the previous distance estimate of 6 kpc based on a kinematic distance. This drastic change places the source in the Perseus arm rather than in the Outer arm. Combination of the distance and the proper motions with the systemic velocity provides a rotation velocity of 227+9−11 km s−1 at the source assuming Θ0 = 240 km s−1. The result is marginally slower than the rotation velocity at LSR with ~ 1−σ significance, but consistent with previous VLBI results for six sources in the Perseus arm. We also show the averaged disk peculiar motion over the seven sources in the Perseus arm as (Umean, Vmean) = (11 ± 3, −17 ± 3) km s−1. It suggests that the seven sources in the Perseus arm are systematically moving toward the Galactic center, and lag behind the Galactic rotation with more than 3-σ significance.

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.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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