scholarly journals Gaia EDR3 Proper Motions of Milky Way Dwarfs. II Velocities, Total Energy, and Angular Momentum

2021 ◽  
Vol 922 (2) ◽  
pp. 93
Author(s):  
Francois Hammer ◽  
Jianling Wang ◽  
Marcel S. Pawlowski ◽  
Yanbin Yang ◽  
Piercarlo Bonifacio ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Total Energy ◽  
Large Scale ◽  
Milky Way ◽  
Radial Velocities ◽  
Proper Motions ◽  
Satellite Systems ◽  
Angular Momenta ◽  
Total Energies ◽  
Mass Profile

Abstract Here we show that precise Gaia EDR3 proper motions have provided robust estimates of 3D velocities, angular momentum, and total energy for 40 Milky Way dwarfs. The results are statistically robust and are independent of the Milky Way mass profile. Dwarfs do not behave like long-lived satellites of the Milky Way because of their excessively large velocities, angular momenta, and total energies. Comparing them to other MW halo populations, we find that many are at first passage, ≤2 Gyr ago, i.e., more recent than the passage of Sagittarius, ∼4–5 Gyr ago. We suggest that this is in agreement with the stellar populations of all dwarfs, for which we find that a small fraction of young stars cannot be excluded. We also find that dwarf radial velocities contribute too little to their kinetic energy when compared to satellite systems with motions only regulated by gravity, and some other mechanism must be at work such as ram pressure. The latter may have preferentially reduced radial velocities when dwarf progenitors entered the halo until they lost their gas. It could also explain why most dwarfs lie near their pericenter. We also discover a novel large-scale structure perpendicular to the Milky Way disk, which is made by 20% of dwarfs orbiting or counter-orbiting with the Sagittarius dwarf.

scholarly journals The Status of Absolute Proper Motions and the Kinematics of Globular Clusters

1995 ◽  
Vol 164 ◽  
pp. 406-406 ◽  
Author(s):  
M. Geffert ◽  
B. Dauphole ◽  
J. Colin ◽  
M. Odenkirchen ◽  
H.-J. Tucholke ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Radial Velocities ◽  
Proper Motions ◽  
Preliminary Results ◽  
Space Motion ◽  
The Status ◽  
Galactic Potentials ◽  
Total Energies

We have studied a sample of 26 globular clusters for which so far absolute proper motions exist in the literature. The proper motions were combined with distances and radial velocities for a determination of the space motion of the clusters. Using different galactic potentials (see Dauphole & Colin 1994 and references therein) we calculated the orbits of the globular clusters and their time averaged eccentricities, total energies, and apo- and perigalactic distances. The relation of the orbital quantities to the metallicities of the globular clusters has been studied. Preliminary results of this study were presented in Geffert et al. (1993).

scholarly journals The Milky Way’s disc of classical satellite galaxies in light of Gaia DR2

2019 ◽  
Vol 491 (2) ◽  
pp. 3042-3059 ◽  
Author(s):  
Marcel S Pawlowski ◽  
Pavel Kroupa
Keyword(s):  
Wide Distribution ◽  
Independent Data ◽  
Proper Motions ◽  
Underlying Distribution ◽  
Satellite Systems ◽  
Angular Momenta ◽  
Recent Group ◽  
Satellite Galaxies ◽  
Gaia Dr2 ◽  
True Correlation

ABSTRACT We study the correlation of orbital poles of the 11 classical satellite galaxies of the Milky Way, comparing results from previous proper motions with the independent data by Gaia DR2. Previous results on the degree of correlation and its significance are confirmed by the new data. A majority of the satellites co-orbit along the Vast Polar Structure, the plane (or disc) of satellite galaxies defined by their positions. The orbital planes of eight satellites align to <20° with a common direction, seven even orbit in the same sense. Most also share similar specific angular momenta, though their wide distribution on the sky does not support a recent group infall or satellites-of-satellites origin. The orbital pole concentration has continuously increased as more precise proper motions were measured, as expected if the underlying distribution shows true correlation that is washed out by observational uncertainties. The orbital poles of the up to seven most correlated satellites are in fact almost as concentrated as expected for the best-possible orbital alignment achievable given the satellite positions. Combining the best-available proper motions substantially increases the tension with ΛCDM cosmological expectations: <0.1 per cent of simulated satellite systems in IllustrisTNG contain seven orbital poles as closely aligned as observed. Simulated systems that simultaneously reproduce the concentration of orbital poles and the flattening of the satellite distribution have a frequency of <0.1 per cent for any number of k > 3 combined orbital poles, indicating that these results are not affected by a look-elsewhere effect. This compounds the Planes of Satellite Galaxies Problem.

scholarly journals Local RR Lyrae stars: native and alien

2019 ◽  
Vol 492 (2) ◽  
pp. 2161-2176 ◽  
Author(s):  
R Zinn ◽  
X Chen ◽  
A C Layden ◽  
D I Casetti-Dinescu
Keyword(s):  
Milky Way ◽  
Large Magellanic Cloud ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Angular Momenta ◽  
Data Release ◽  
Total Energies ◽  
Using Data ◽  
Lyrae Stars ◽  
Existing Data

ABSTRACT Measurements of [Fe/H] and radial velocity are presented for 89 RR Lyrae (RRL) candidates within 6 kpc of the Sun. After the removal of two suspected non-RRLs, these stars were added to an existing data base, which yielded 464 RRLs with [Fe/H] on a homogeneous scale. Using data from the Gaia satellite (Data Release 2), we calculated the positions and space velocities for this sample. These data confirm the existence of a thin disc of RRL with [α/Fe] ∼ solar. The majority of the halo RRLs with large total energies have near-zero angular momenta about the Z-axis. Kinematically, these stars closely resemble the Gaia-Sausage/Gaia-Enceladus stars that others have proposed are debris from the merger of a large galaxy with the Milky Way. The metallicity and period distributions of the RRLs and their positions in the period–amplitude diagram suggest that this disrupted galaxy was as massive as the Large Magellanic Cloud and possibly greater.

scholarly journals Measuring the Stellar Halo Velocity Anisotropy With 3D Kinematics

2015 ◽  
Vol 11 (S317) ◽  
pp. 288-289
Author(s):  
Emily C. Cunningham ◽  
Alis J. Deason ◽  
Puragra Guhathakurta ◽  
Constance M. Rockosi ◽  
Roeland P. van der Marel ◽  
...  
Keyword(s):  
Milky Way ◽  
Anisotropy Parameter ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
Line Of Sight ◽  
Proper Motions ◽  
Velocity Anisotropy ◽  
Halo Stars ◽  
Stellar Halo ◽  
Kinematic Information

AbstractWe present the first measurement of the anisotropy parameter β using 3D kinematic information outside of the solar neighborhood. Our sample consists of 13 Milky Way halo stars with measured proper motions and radial velocities in the line of sight of M31. Proper motions were measured using deep, multi-epoch HST imaging, and radial velocities were measured from Keck II/DEIMOS spectra. We measure β = −0.3−0.9+0.4, which is consistent with isotropy, and inconsistent with measurements in the solar neighborhood. We suggest that this may be the kinematic signature of a relatively early, massive accretion event, or perhaps several such events.

scholarly journals The RAVE harvest: from the relation between abundances and kinematic of the Milky Way stars to tools for the abundance analysis of the spectra

2013 ◽  
Vol 9 (S298) ◽  
pp. 292-297
Author(s):  
Corrado Boeche ◽  
Keyword(s):  
Milky Way ◽  
Radial Velocities ◽  
Proper Motions ◽  
Chemical Abundances ◽  
Stellar Spectra ◽  
Chemical Gradients ◽  
Single Process ◽  
The Galaxy ◽  
Nearby Stars ◽  
Kinematic Information

AbstractRAVE is a spectroscopic survey of the Milky Way which collected more than 500,000 stellar spectra of nearby stars in the Galaxy. The RAVE consortium analysed these spectra to obtain radial velocities, stellar parameters and chemical abundances. These data, together with spatial and kinematic information like positions, proper motions, and distance estimations, make the RAVE database a rich source for galactic archaeology. I present recent investigations on the chemo-kinematic relations and chemical gradients in the Milky Way disk using RAVE data and compare our results with the Besançon models. I also present the code SPACE, an evolution of the RAVE chemical pipeline, which integrates the measurements of stellar parameters and chemical abundances in one single process.

scholarly journals Maser Astrometry: from Galactic Structure to Local Group Cosmology

2012 ◽  
Vol 8 (S287) ◽  
pp. 359-367 ◽  
Author(s):  
Mark J. Reid
Keyword(s):  
Large Scale ◽  
Massive Star ◽  
Milky Way ◽  
Local Group ◽  
Galactic Structure ◽  
Proper Motions ◽  
Star Forming ◽  
Fundamental Parameters ◽  
3 Dimensional ◽  
Star Forming Regions

AbstractThis review summarizes current advances in astrometry of masers as they pertain to large-scale Galactic structure and dynamics and Local Group cosmology. Parallaxes and proper motions have now been measured for more than 60 massive star forming regions using the Japanese VERA array, the EVN and the VLBA. These results provide “gold standard” distances and 3-dimensional velocities for sources across the Milky Way, revealing its spiral structure. Modeling these data tightly constrains the fundamental parameters of the Milky Way: R0 and Θ0. Proper motions of Local Group galaxies have been measured, improving our understanding of the history and fate of the Group.

scholarly journals The Mass Distribution of the Milky Way Deduced from Globular Cluster Dynamics

1996 ◽  
Vol 169 ◽  
pp. 697-702 ◽  
Author(s):  
B. Dauphole ◽  
J. Colin ◽  
M. Geffert ◽  
M. Odenkirchen ◽  
H.-J. Tucholke
Keyword(s):  
Spatial Distribution ◽  
Mass Distribution ◽  
Globular Cluster ◽  
Total Mass ◽  
Globular Clusters ◽  
Large Scale ◽  
Milky Way ◽  
Proper Motions ◽  
Orbital Parameters ◽  
Galactic Potential

We present here a new analytical Galactic potential. We used the constraint of galactic globular cluster dynamics compared to their spatial distribution. This was done with the help of the globular clusters' proper motions. The result for the clusters dynamics show a better agreement between orbital parameters and statistical distribution of the studied globular clusters than in previous published potentials. The globular cluster dynamics constrain the mass distribution on a large scale, until 40 kpc from the centre. In this model, the total mass for the Milky Way is 7.9 1011 M⊙.

scholarly journals A spectroscopic survey of late-type giants in the Milky Way disk and local halo substructure

2007 ◽  
Vol 3 (S248) ◽  
pp. 506-507
Author(s):  
A. A. Sheffield ◽  
S. R. Majewski ◽  
A. M. Cheung ◽  
C. M. Hampton ◽  
J. D. Crane ◽  
...  
Keyword(s):  
High Velocity ◽  
Milky Way ◽  
Stellar Populations ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
Proper Motions ◽  
Late Type ◽  
Halo Stars ◽  
Medium Resolution ◽  
Galactic Stellar Populations

AbstractWe report the results of a survey of late-type giants aimed at understanding the nature of the disk and nearby halo Galactic stellar populations. We have obtained medium resolution (2–4 Å) spectra for 749 late K and early M giants at mid-latitudes selected from the 2MASS catalog with the FOBOS system at Fan Mountain Observatory. These spectra provide radial velocities (RVs) at the 5 km s−1 level, spectroscopic [Fe/H] good to σ[Fe/H] = 0.25 dex, and information on the relative abundances of Mg/Fe and Na/Fe in these stars. Proper motions from UCAC2 are used to search for local substructures, in particular the leading arm of the Sagittarius tidal streamer passing through the solar neighborhood. The combined proper motions and RVs yield full 6D stellar space motions. We have, by way of kinematics, relatively cleanly isolated the thick disk from the typically high velocity substructures that compose the nearby halo.We find evidence for substructure in the kinematics and metallicities of local halo stars.

scholarly journals Gas accretion and galactic fountain flows in the Auriga cosmological simulations: angular momentum and metal redistribution

2019 ◽  
Vol 490 (4) ◽  
pp. 4786-4803 ◽  
Author(s):  
Robert J J Grand ◽  
Freeke van de Voort ◽  
Jolanta Zjupa ◽  
Francesca Fragkoudi ◽  
Facundo A Gómez ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Milky Way ◽  
Galactocentric Distance ◽  
Cosmological Simulations ◽  
Satellite Systems ◽  
Secular Evolution ◽  
Rotation Axes ◽  
Momentum Plane ◽  
Minor Mergers ◽  
Gas Accretion

ABSTRACT Using a set of 15 high-resolution magnetohydrodynamic cosmological simulations of Milky Way formation, we investigate the origin of the baryonic material found in stars at redshift zero. We find that roughly half of this material originates from subhalo/satellite systems and half is smoothly accreted from the intergalactic medium. About $90 {{\ \rm per\ cent}}$ of all material has been ejected and re-accreted in galactic winds at least once. The vast majority of smoothly accreted gas enters into a galactic fountain that extends to a median galactocentric distance of ∼20 kpc with a median recycling time-scale of ∼500 Myr. We demonstrate that, in most cases, galactic fountains acquire angular momentum via mixing of low angular momentum, wind-recycled gas with high angular momentum gas in the circumgalactic medium (CGM). Prograde mergers boost this activity by helping to align the disc and CGM rotation axes, whereas retrograde mergers cause the fountain to lose angular momentum. Fountain flows that promote angular momentum growth are conducive to smooth evolution on tracks quasi-parallel to the disc sequence of the stellar mass-specific angular momentum plane, whereas retrograde minor mergers, major mergers, and bar-driven secular evolution move galaxies towards the bulge sequence. Finally, we demonstrate that fountain flows act to flatten and narrow the radial metallicity gradient and metallicity dispersion of disc stars, respectively. Thus, the evolution of galactic fountains depends strongly on the cosmological merger history and is crucial for the chemodynamical evolution of Milky-Way-sized disc galaxies.

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