scholarly journals On the Kinematics of Tidal Debris from Omega Cen's Progenitor Galaxy

2004 ◽  
Vol 21 (2) ◽  
pp. 237-241 ◽  
Author(s):  
Masashi Chiba ◽  
Arihiro Mizutani
Keyword(s):  
Dynamical Evolution ◽  
The Sun ◽  
Retrograde Motion ◽  
The North ◽  
Satellite Galaxy ◽  
Flat Disk ◽  
The Galaxy ◽  
Galactic Longitude ◽  
North Galactic ◽  
Kinematic Properties

AbstractThe kinematic properties of tidal debris from an orbiting Galactic satellite is presented, on the assumption that its central part once contained the most massive Galactic globular cluster, ω Cen. We simulate dynamical evolution of a satellite galaxy that follows the present-day and likely past orbits of ω Cen, and analyse the kinematic nature of their tidal debris and randomly generated Galactic stars comprising spheroidal halo and flat disk components. It is found that the debris stars show a retrograde rotation at ∼–100 km s–1, which may accord with a recently discovered stellar stream at a radial velocity of ∼300 km s–1 towards the Galactic longitude of ∼270°. These stars also contribute, only in part, to a reported retrograde motion of the outer halo in the north Galactic pole direction, without significantly modifying local halo kinematics near the Sun. The prospects for future debris searches and the implications for the early evolution of the Galaxy are briefly presented.

scholarly journals Vertical structure and kinematics of the Galactic outer disk

2019 ◽  
Vol 72 (4) ◽  
Author(s):  
Nobuyuki Sakai ◽  
Takumi Nagayama ◽  
Hiroyuki Nakanishi ◽  
Nagito Koide ◽  
Tomoharu Kurayama ◽  
...  
Keyword(s):  
Dwarf Galaxy ◽  
Oscillatory Behavior ◽  
Maximum Height ◽  
Galactocentric Distance ◽  
The North ◽  
Vertical Density ◽  
Galactic Longitude ◽  
Maser Sources ◽  
Galactic Warp ◽  
North Galactic

Abstract We report on measurements of parallax and proper motion for four 22 GHz water maser sources as part of the VERA Outer Rotation Curve project. All the sources show Galactic latitudes of >2° and Galactocentric distances of >11 kpc at the Galactic longitude range of 95° < l < 126°. The sources trace the Galactic warp reaching to 200–400 pc, and also the signature of the warp to 600 pc toward the north Galactic pole. The new results, along with previous results in the literature, show that the maximum height of the Galactic warp increases with Galactocentric distance. Also, we examined velocities perpendicular to the disk for the sample, and found oscillatory behavior between the vertical velocities and Galactic heights. This behavior suggests the existence of bending (vertical density) waves, possibly induced by a perturbing satellite (e.g., the passage of the Sagittarius dwarf galaxy).

scholarly journals Deep Multi-Colour Starcounts

1994 ◽  
Vol 161 ◽  
pp. 423-424
Author(s):  
I.N. Reid ◽  
S.R. Majewski
Keyword(s):  
Standard Model ◽  
Stellar Population ◽  
Stellar Populations ◽  
The North ◽  
Halo Stars ◽  
The Standard Model ◽  
The Galaxy ◽  
Best Fitting ◽  
Galactic Stellar Populations ◽  
North Galactic

Starcounts remain one of the most effective methods of probing the structure of the Galactic stellar populations. However, studies of the distribution at large distances above the Plane demand accurate photometry extending to faint magnitudes (V > 20), and such datasets are still rare. We (Reid & Majewski 1993) have analyzed data from one field — Majewski's (1992) UJF observations of SA57, the North Galactic Pole field. Our results revealed significant discrepancies with the standard model of the Galaxy (see refs. in Reid & Majewski), notably a paucity in the number of halo stars by a factor of two and the presence of a factor of two more disk stars than predicted — sufficient stars that the disk is the majority stellar population, outnumbering halo stars 2:1 even at V = 21. Majewski et al. (1993) has obtained UJFN photographic data for several other fields, and Fig. 1 shows a preliminary comparison of these observations with the predictions of the best-fitting SA57 model. Given that none of the parameters have been modified, the agreement is surprisingly good.

scholarly journals Vertical Metallicity Gradient of the Galaxy Based on UBV Starcount Data

1994 ◽  
Vol 161 ◽  
pp. 420-422
Author(s):  
T. Yamagata ◽  
Y. Yoshii
Keyword(s):  
Spatial Distribution ◽  
Least Squares ◽  
High Latitude ◽  
Vertical Gradient ◽  
Thin Disk ◽  
Thick Disk ◽  
The North ◽  
The Galaxy ◽  
Metal Abundance ◽  
North Galactic

The spatial distribution of metal abundance in the Galaxy has been analyzed using the UBV starcount data recently obtained in two high-latitude regions of the North Galactic Pole (NGP) and Selected Area 54 (SA54). A least-squares analysis was performed to determine the vertical metallicity gradient for each of the thin and thick disk components that gives a reasonable fit to the observed U-B and B-V colour distributions to V = 18 mag. The most probable value of the vertical gradient is obtained as d[Fe/H]/dz = −0.5 kpc−1 for the thin disk, and −0.1 kpc−1 for the thick disk.

scholarly journals Studies of 0-F5 stars at the Galactic poles

1985 ◽  
Vol 106 ◽  
pp. 163-164
Author(s):  
R. W. Hilditch ◽  
A.D. Mcfadzean ◽  
Graham Hill ◽  
J. V. Barnes
Keyword(s):  
Chemical Evolution ◽  
Galactic Plane ◽  
Early Type ◽  
Population Groups ◽  
The North ◽  
The Galaxy ◽  
Early Type Stars ◽  
Velocity Dispersions ◽  
North And South ◽  
Kinematic Properties

We report progress on a spectroscopic and photometric programme devoted to the study of the dynamics of O-F5 stars within 15° of the North and South Galactic Poles. The aims of the programme are to test dynamical and chemical evolution models of the Galaxy by establishing velocity dispersions as a function of z-distance for stars of different population groups. We are also able to investigate the interstellar reddening at the poles and the kinematic properties of apparently normal early-type stars found more than 1 kpc from the galactic plane.

scholarly journals The Gravitational Field of the Galaxy in the Z Direction

1977 ◽  
Vol 4 (2) ◽  
pp. 65-66
Author(s):  
R. F. Griffin
Keyword(s):  
Galactic Plane ◽  
Narrow Band ◽  
Radial Velocities ◽  
Photoelectric Photometry ◽  
Giant Stars ◽  
The North ◽  
The Galaxy ◽  
Absolute Magnitudes ◽  
North Galactic ◽  
K Giants

This is a progress report of a project designed to find the component, perpendicular to the Galactic plane, of the gravitational potential of the Galaxy. The principle is to measure the radial velocities and distances of a large number of K-giant stars near the North Galactic Pole. My student G. A. Radford is masterminding the project; collaborating with us are Drs. J. E. Gunn of the Hale Observatories and L. Hansen and K. Gyldenkerne of Copenhagen.We have measured the radial velocities of all the HD stars of type KO and later, and many of the G5 stars, within 15°of the Galactic Pole, using the Cambridge photoelectric spectrometer. In addition, we have observed all the stars classified as K giants by Upgren in his declination zones 25° to 31°, using the spectrometer on the Hale telescope. There are about 900 stars observed altogether, including about 200 Upgren stars, running down to twelfth magnitude or so, which are not in the Henry Draper Catalogue. To determine the distances of all these stars we are now trying to determine the absolute magnitudes by narrow-band photoelectric photometry in the Copenhagen system. Most of the observations have been made, thanks largely to the very generous grants of observing time given by the Hale Observatories earlier this year; but the reductions have only been completed for about 300 stars (including 244 K giants) which were observed last year at Kitt Peak, and the present, very preliminary, discussion is based on those stars alone.

Investigation of the kinematics and structure of the Galaxy in the vicinity of the North galactic pole

1994 ◽  
Vol 315 (4) ◽  
pp. 291-301 ◽  
Author(s):  
N. Kharchenko ◽  
E. Schilbach ◽  
R.-D. Scholz
Keyword(s):  
The North ◽  
The Galaxy ◽  
North Galactic

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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