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Vertically extended, high velocity dispersion stellar distributions appear to be a ubiquitous feature of disc galaxies, and both internal and external mechanisms have been proposed to be the major driver of their formation. However, it is…

We perform numerical simulations of a stellar galactic disk with initial conditions chosen to represent an unrelaxed population which might have been left following a merger. Stars are unevenly distributed in radial action angle, though the…

Astrophysics of Galaxies · Physics 2009-11-13 I. Minchev , A. C. Quillen , M. Williams , K. C. Freeman , J. Nordhaus , A. Siebert , O. Bienayme

The Hercules kinematic group is a stellar anomaly structure observed in the solar neighbourhood (SNd). In the previous paper, we analysed chemical signatures and related the origin of this stellar population to the outer bar. Next to…

Astrophysics of Galaxies · Physics 2025-04-22 Yusen Li , Kenneth Freeman , Helmut Jerjen

We present and discuss new determinations of metallicity, rotation, age, kinematics, and Galactic orbits for a complete, magnitude-limited, and kinematically unbiased sample of 16,682 nearby F and G dwarf stars. Our 63,000 new, accurate…

We search for the existence of chemically-distinct stellar components in the solar neighbourhood using published data. Extending earlier work, we show that when the abundances of Fe, alpha elements, and the r-process element Eu are…

Astrophysics of Galaxies · Physics 2015-05-19 Julio F. Navarro , Mario G. Abadi , Kim A. Venn , Kenneth C. Freeman , Borja Anguiano

The local velocity field of young stars is dominated by the galactic rotation, the kinematics of the Gould Belt and the nearest OB associations and open clusters, and the kinematics of the spiral structure. We re-examined here this local…

Astrophysics · Physics 2007-05-23 J. Torra , D. Fernandez , F. Figueras

Over the last decade, several groups of young (mainly low-mass) stars have been discovered in the solar neighbourhood (closer than ~100 pc), thanks to cross-correlation between X-ray, optical spectroscopy and kinematic data. These young…

Astrophysics · Physics 2015-05-13 D. Fernandez , F. Figueras , J. Torra

[Abridge] In the first paper of this series (paper I) we presented a new approach for studying the chemo-odynamical evolution in disk galaxies, focusing on the Milky Way. Here we extend these results to different distances from the Galactic…

Astrophysics of Galaxies · Physics 2014-12-03 Ivan Minchev , Cristina Chiappini , Marie Martig

We use about 15,000 F/G nearby dwarf stars selected from the LAMOST pilot survey to map the U-V velocity distribution in the solar neighbourhood. An extreme deconvolution algorithm is applied to reconstruct an empirical multi-Gaussian…

Astrophysics of Galaxies · Physics 2014-12-17 Qiran Xia , Chao Liu , Yan Xu , Shude Mao , Shuang Gao , Yonghui Hou , Ge Jin , Yong Zhang

Using the MIKE spectrograph, mounted on the 6.5 m Magellan/Clay telescope at the Las Campanas observatory in Chile, we have obtained high-resolution spectra for 60 F and G dwarf stars, all likely members of a density enhancement in the…

Astrophysics · Physics 2009-05-28 T. Bensby , M. S. Oey , S. Feltzing , B. Gustafsson

The evolution of the Milky Way disk, which contains most of the stars in the Galaxy, is affected by several phenomena. For example, the bar and the spiral arms of the Milky Way induce radial migration of stars and can trap or scatter stars…

The true nature of the Hyades and Sirius superclusters is still an open question. In this contribution, we confront Eggen's hypothesis that they are cluster remnants with the results of a kinematic analysis of more than 6000 K and M giants…

Astrophysics · Physics 2007-05-23 B. Famaey , A. Jorissen , X. Luri , M. Mayor , S. Udry , H. Dejonghe , C. Turon

We illustrate the formation and evolution of the Milky Way over cosmic time, utilizing a sample of 10 million red giant stars with full chemodynamical information, including metallicities and $\alpha$-abundances from low-resolution Gaia XP…

The Milky Way is a unique laboratory, where stellar properties can be measured and analyzed in detail. In particular, stars in the older populations encode information on the mechanisms that led to the formation of our Galaxy. In this…

We present a study of the hierarchical clustering of the young stellar clusters in six local (3--15 Mpc) star-forming galaxies using Hubble Space Telescope broad band WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy…

Within disk galaxies, the velocity dispersion, $\sigma$, of stars increases with age, $\tau$, as measured in the Milky Way (MW) and nearby galaxies. This relation provides a key window into galactic formation history, tracing both the…

Astrophysics of Galaxies · Physics 2025-06-16 Fiona McCluskey , Andrew Wetzel , Sarah Loebman , Jorge Moreno

The Ursa Major Moving Group (UMa) is one of the closest stellar associations, yet its age has remained controversial, with published estimates ranging from 200 Myr to 1 Gyr. We present a comprehensive age analysis using the largest sample…

Solar and Stellar Astrophysics · Physics 2026-01-15 Julia Sheffler , Max Clark , Melinda Soares-Furtado , Adam Distler , Ritvik Sai Narayan , Jenna Karcheski , Kenneth Nordsieck

We present the results of a study of the stellar activity in the solar neighborhood using complete kinematics (galactocentric velocities U,V,W) and the chromospheric activity index $\log R'_{\rm{HK}}$. We analyzed the average activity level…

Solar and Stellar Astrophysics · Physics 2015-06-15 F. Murgas , J. S. Jenkins , P. Rojo , H. R. A Jones , D. J. Pinfield

The study of the Milky Way stellar discs in the context of galaxy formation is discussed. In particular we explore the properties of the Milky Way disc using a new sample of about 550 dwarf stars for which we have recently obtained…

Astrophysics · Physics 2009-11-13 S. Feltzing , T. Bensby

The space velocities from the catalog of Nordstrom et al. (2004) are used to trace variations of a number of kinematic parameters of single F and G dwarfs as a function of their age. The vertex deviation of disk stars increases from 7+- 1…

Astrophysics · Physics 2009-06-23 Vadim V. Bobylev , Anisa T. Bajkova
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