157 research outputs found
Stellar Stream Candidates in the Solar Neighborhood Found in the LAMOST DR3 and TGAS
We have cross-matched the LAMOST DR3 with the Gaia DR1 TGAS catalogs and
obtained a sample of 166,827 stars with reliable kinematics. A technique based
on the wavelet transform was applied to detect significant overdensities in
velocity space among five subsamples divided by spatial position. In total, 16
significant overdensities of stars with very similar kinematics were
identified. Among these, four are new stream candidates and the rest are
previously known groups. Both the U-V velocity and metallicity distributions of
the local sample show a clear gap between the Hercules structure and the
Hyades-Pleiades structure. The U-V positions of these peaks shift with the
spatial position. Following a description of our analysis, we speculate on
possible origins of our stream candidates.Comment: 16 pages, 5 figure
Satellite galaxies' drag on field stars in the Milky Way
With Gaia EDR3 data, velocity dispersion of Milky Way field stars around
satellite galaxies have been investigated. We have fitted velocity dispersion
against distance to satellite galaxy and found the gradient of velocity
dispersion is related to the mass of satellite galaxy. With order-of-magnitude
approximations, a linear correlation has been fitted between the mass of
satellite galaxy and gradient of velocity dispersion caused by its
gravitational drag. Though our result is an observational qualitative result,
it shows better relation could be obtained with more observations in the
future.Comment: 8 pages, 3 figure
Nearly 30,000 Late-Type Main-Sequence Stars with Stellar Age from LAMOST DR5
We construct a sample of nearly 30,000 main-sequence stars with 4500K \u3c Teff \u3c 5000K and stellar ages estimated by the chromospheric activity−age relation. This sample is used to determine the age distribution in the R − Z plane of the Galaxy, where R is the projected Galactocentric distance in the disk midplane and Z is the height above the disk midplane. As |Z| increases, the percentage of old stars becomes larger. It is known that scale-height of Galactic disk increases as R increases, which is called flare. A mild flare from R ∼ 8.0 to 9.0 kpc in stellar age distribution is found. We also find that the velocity dispersion increases with age as confirmed by previous studies. Finally we present spiral-shaped structures in Z − υZ phase space in three stellar age bins. The spiral is clearly seen in the age bin of [0, 1] Gyr, which suggests that a vertical perturbation to the disk probably took place within the last ∼ 1.0 Gyr
On the Migration Origin of the Hercules Moving Group with GAIA, LAMOST, APOGEE, and GALAH Surveys
Using Gaia DR3 data and the wavelet transformation technique, we study the
substructures of the Hercules moving group (HMG): Hercules 1 (H1) and Hercules
2 (H2). Spectroscopic survey data from LAMOST, APOGEE, and GALAH are used to
obtain metallicities and ages of stars belonging to the HMG. Our analysis leads
to several key findings as follows: () the HMG is on average richer in
metallicity than the Galactic disk, with H2 being metal richer than H1; ()
the HMG likely has a radial metallicity gradient distinct from that of the
disk; () the HMG is on average older than the disk, with H2 being older than
H1; () the HMG likely has a radial age gradient distinct from that of the
disk; and () the metallicity and age distributions of the HMG depend mainly
on the Galactic radius but show no dependence on the azimuthal velocity. Taken
all together, we conclude that the HMG is composed primarily of stars
undergoing radial migration. We suggest that the HMG is associated with a
higher-order dynamical resonance of the bar of the Galaxy.Comment: 15 pages, 6 figures. Accepted by Ap
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