The Magellanic System

1985 ◽  
Vol 6 (1) ◽  
pp. 104-109 ◽  
Author(s):  
D. S. Mathewson
Keyword(s):  
Globular Clusters ◽  
Neutral Hydrogen ◽  
Close Encounter ◽  
Polar Ring ◽  
Ram Pressure ◽  
Cepheid Variables ◽  
Ultimate Fate ◽  
Magellanic Stream ◽  
Gaseous Halo ◽  
Magellanic System

AbstractThis review concentrates on observations of neutral hydrogen in the Magellanic System, and what they reveal about the structure, dynamics, evolution and ultimate fate of the LMC and SMC. Some recent observations of 161 Cepheid variables in the SMC are used together with the HI observations to determine the geometry of the SMC. These show that it has an amazing depth of at least 30 kpc. To explain the results it is proposed that the SMC had a close encounter with the LMC which has warped the disk of the LMC, produced the bridge between the two galaxies and tidally fissioned the SMC. The SMC is in the process of irreversible disintegration. It is believed that the Magellanic Clouds are not bound to our Galaxy and approached us from the direction of Andromeda. They may have had a close encounter with Andromeda 3 x 109 years ago, which may explain the massive starburst which occurred in the LMC and SMC at that time. It is believed that the Magellanic Stream has been swept out of the inter-Cloud region by the ram pressure of the gaseous halo of our Galaxy. If dynamic friction is sufficient for the Clouds to be captured and to eventually collide with our Galaxy, a polar ring will be formed similar to that observed in some other galaxies. The polar ring of dwarf spheroidals and outlying globular clusters at present encircling our Galaxy may be the remnants of a previous collision with some other galaxy 6 x 109 years ago.

scholarly journals The Kinematics of the Magellanic Clouds

1995 ◽  
Vol 166 ◽  
pp. 273-282
Author(s):  
B.E. Westerlund
Keyword(s):  
Galactic Halo ◽  
Neutral Hydrogen ◽  
Magellanic Clouds ◽  
Great Promise ◽  
Common Envelope ◽  
The Past ◽  
Ram Pressure ◽  
Long Time ◽  
Magellanic Stream ◽  
Magellanic System

It is essential for our understanding of the evolution of the Magellanic System, comprising the Large and the Small Magellanic Cloud, the Intercloud or Bridge region and the Magellanic Stream, to know its motions in the past. The Clouds have a common envelope of neutral hydrogen; this indicates that they have been bound to each others for a long time. The Magellanic System moves in the gravitational potential of our Galaxy; it is exposed to ram pressure through its movement in the galactic halo. Both effects ought to be noticeable in their present structure and kinematics. It is generally assumed, but not definitely proven, that the Clouds have been bound to our Galaxy for at least the last 7 Gyr. Most models assume that the Clouds lead the Magellanic Stream. The interaction between the Clouds has influenced their structure and kinematics severely. The effects should be possible to trace in the motions of their stellar and gaseous components as pronounced disturbances. Recent astrometric contributions in this field show a great promise for the future if still higher accuracy can be achieved.

scholarly journals The Effect of Drag from the Galactic Hot Halo on the Magellanic Stream and Leading Arm

2011 ◽  
Vol 28 (2) ◽  
pp. 117-127 ◽  
Author(s):  
Jonathan Diaz ◽  
Kenji Bekki
Keyword(s):  
Density Gradient ◽  
Column Density ◽  
Numerical Models ◽  
Neutral Hydrogen ◽  
Magellanic Clouds ◽  
Negative Effects ◽  
Global Properties ◽  
Ram Pressure ◽  
Magellanic Stream ◽  
Drag Term

AbstractWe study the effect of drag induced by the Galactic hot halo on the two neutral hydrogen (HI) cloud complexes associated with the Large and Small Magellanic Clouds: the Magellanic Stream (MS) and the Leading Arm (LA). In particular, we adopt the numerical models of previous studies and re-simulate the tidal formation of the MS and LA with the inclusion of a drag term. We find that the drag has three effects which, although model-dependent, may bring the tidal formation scenario into better agreement with observations: correcting the LA kinematics, reproducing the MS column density gradient, and enhancing the formation of MS bifurcation. We furthermore propose a two-stage mechanism by which the bifurcation forms. In general, the inclusion of drag has a variety of both positive and negative effects on the global properties of the MS and LA, including their on-sky positions, kinematics, radial distances, and column densities. We also provide an argument which suggests that ram-pressure stripping and tidal stripping are mutually exclusive candidates for the formation of the MS and LA.

scholarly journals A Search for Tidal Stellar Debris from the Magellanic Clouds: Survey Results from the First Two Years

1999 ◽  
Vol 190 ◽  
pp. 508-510 ◽  
Author(s):  
S. R. Majewski ◽  
J. C. Ostheimer ◽  
W. E. Kunkel ◽  
K. V. Johnston ◽  
R. J. Patterson ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Halo ◽  
Large Magellanic Cloud ◽  
Main Sequence Stars ◽  
Tidal Disruption ◽  
Negative Results ◽  
Ram Pressure ◽  
Survey Results ◽  
Magellanic Stream

An important discriminant between leading models for the origin of the Magellanic Stream is the presence of a stellar counterpart to the HI gas stream: ram pressure stripping of gas by a putative hot Galactic halo would act only on Magellanic gas while gravitational tidal stripping would act on both gas and stars. Several previous attempts to find tidal stellar debris have failed to find carbon stars, A stars, or other main sequence stars in the Magellanic Stream (Mathewson et al. 1979; Recillas-Cruz 1982; Brück & Hawkins 1983; Guhathakurta & Lin 1999). However, there has long been a suggestion (Kunkel 1979; Lynden-Bell 1982) of a possible Magellanic association of satellite galaxies and globular clusters that have similar orbits and may derive from the break up of a greater Magellanic galaxy (Lynden-Bell & Lynden-Bell 1995; Majewski et al. 1997). Recent models (Moore & Davis 1994; Johnston 1998) of the tidal disruption of Large Magellanic Cloud (LMC)-like systems indicate a wide dispersal of debris, much wider than the rather confined HI stream, so that the contrast of tidal debris against the Galactic fore/background would be low. If true, this could explain some of the previous negative results for tidal debris searches.

A Drag Dominated Model of the Magellanic Stream

1985 ◽  
Vol 6 (2) ◽  
pp. 195-198 ◽  
Author(s):  
Gerhardt R. Meurer ◽  
G. V. Bicknell ◽  
R. A. Gingold
Keyword(s):  
Magellanic Clouds ◽  
Radial Velocities ◽  
Tidal Model ◽  
Drag Forces ◽  
Wide Range ◽  
Magellanic Stream ◽  
Gaseous Halo ◽  
Gas Drag ◽  
Magellanic System

AbstractWe present here the best of a series of models of the Magellanic stream. The dominant force in these models is gas drag. Gaseous cloudlets are torn from the bridge between the Large and Small Magellanic Clouds as the Magellanic system passes through a hot gaseous halo about our galaxy. The cloudlets are then stretched apart from each other by tidal and drag forces to form the Magellanic stream. Our best model closely reproduces the position of the stream on the sky and the run of radial velocities along the Magellanic stream. The agreement is almost as good as the best purely tidal model. In our best model the Magellanic system is only loosely bound to our galaxy and is on the first encounter with it. This overcomes some of the problems with purely tidal models. Our series of models indicate that there is a wide range of parameters that will produce a reasonable stream under the forces of gas drag and gravity.

The ‘High Velocity Cloud’ Origin of the Magellanic System

1987 ◽  
Vol 7 (1) ◽  
pp. 19-25 ◽  
Author(s):  
D. S. Mathewson ◽  
S. R. Wayte ◽  
V. L. Ford ◽  
K. Ruan
Keyword(s):  
High Velocity ◽  
Galactic Halo ◽  
Magellanic Clouds ◽  
The One ◽  
Magellanic Stream ◽  
Gaseous Halo ◽  
Velocity Cloud ◽  
High Velocity Cloud ◽  
Magellanic System

AbstractIt is believed that the splitting of the SMC into two fragments and the production of the Inter-Cloud gas and the Magellanic Stream occurred in the one event 4 × 108 years ago. This event was a collision between the LMC and SMC. This time is too short for the Stream to be tidal, or be the result of stripping of the Inter-Cloud gas by a diffuse gaseous halo. It is proposed that the clouds in the Stream are the results of collisions between the Inter-Cloud gas and HVCs in the Galactic halo. A model of this process accounts for all of the observational features of the Stream. Observations of HVCs in the path of the Magellanic Clouds are used to predict the development of the Stream. The HVCs in our halo are thought to be a result of a collision of a galaxy with our Galaxy 6 × 109 years ago.

scholarly journals MILKY WAY GLOBULAR CLUSTERS: CLOSE ENCOUNTER RATES WITH EACH OTHER AND WITH THE CENTRAL SUPERMASSIVE BLACK HOLE

REPORTS ◽  
2021 ◽  
Vol 6 (340) ◽  
pp. 94-105
Author(s):  
M.V. Ishchenko ◽  
M.O. Sobolenko ◽  
M.T. Kalambay ◽  
B.T. Shukirgaliyev ◽  
P.P. Berczik
Keyword(s):  
Black Hole ◽  
Globular Clusters ◽  
Milky Way ◽  
Close Encounter ◽  
Encounter Rates ◽  
Supermassive Black Hole

scholarly journals OGLE-ing the Magellanic System: Three-Dimensional Structure

2018 ◽  
Vol 14 (S344) ◽  
pp. 86-89
Author(s):  
Anna M. Jacyszyn-Dobrzeniecka ◽  
Keyword(s):  
Three Dimensional ◽  
Neutral Hydrogen ◽  
Variable Stars ◽  
Dimensional Structure ◽  
Rr Lyrae Stars ◽  
Three Dimensional Structure ◽  
Rr Lyrae ◽  
Classical Cepheids ◽  
Lyrae Stars ◽  
Magellanic System

AbstractWe present a three-dimensional structure of the Magellanic System using over 9 000 Classical Cepheids and almost 23 000 RR Lyrae stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample, we were able to study the Magellanic System in great details.We very carefully studied the distribution of both types of pulsators in the Magellanic Bridge area. We show that there is no evident physical connection between the Clouds in RR Lyrae stars distribution. We only see the two extended structures overlapping. There are few classical Cepheids in the Magellanic Bridge area that seem to form a genuine connection between the Clouds. Their on-sky locations match very well young stars and neutral hydrogen density contours. We also present three-dimensional distribution of classical pulsators in both Magellanic Clouds.

scholarly journals The Polar-Ring Galaxies NGC 2685 and NGC 3808B (W 300)

1990 ◽  
Vol 124 ◽  
pp. 231-244
Author(s):  
V. P. Reshetnikov ◽  
V. A. Yakovleva
Keyword(s):  
Intergalactic Medium ◽  
Close Encounter ◽  
Main Body ◽  
Polar Plane ◽  
Polar Ring ◽  
Ring Galaxies ◽  
Companion Galaxy ◽  
Peculiar Galaxies

Polar-ring galaxies (PRG) are among the most interesting examples of interaction between galaxies. A PRG is a galaxy with an elongated main body surrounded by a ring (or a disk) of stars, gas, and dust rotating in a near-polar plane (Schweizer, Whitmore, and Rubin, 1983). Accretion of matter by a massive lenticular galaxy from either intergalactic medium or a companion galaxy is usually considered as an explanation of the observed structure of PRG. In the latter case there are two possibilities: (1) capture and merging of a neighbor galaxy, and (2) accretion of mass from a companion galaxy during a close encounter. Two PRG formation scenarios just mentioned are illustrated here by the results of our observations of the peculiar galaxies NGC 2685 and NGC 3808B.

Neutral Hydrogen Observations of Eight Globular Clusters

1973 ◽  
Vol 186 ◽  
pp. 831 ◽  
Author(s):  
G. R. Knapp ◽  
W. K. Rose ◽  
F. J. Kerr
Keyword(s):  
Globular Clusters ◽  
Neutral Hydrogen

scholarly journals Young stars raining through the galactic halo: the nature and orbit of price-whelan 1

2019 ◽  
Vol 490 (2) ◽  
pp. 2588-2598 ◽  
Author(s):  
Michele Bellazzini ◽  
Rodrigo A Ibata ◽  
Nicolas Martin ◽  
Khyati Malhan ◽  
Antonino Marasco ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Stellar System ◽  
Young Stars ◽  
Stellar Content ◽  
Velocity Difference ◽  
Ram Pressure ◽  
Magellanic Stream ◽  
Gas Cloud ◽  
Velocity Cloud ◽  
High Velocity Cloud

ABSTRACT We present radial velocities for five member stars of the recently discovered young (age ≃ 100−150 Myr) stellar system Price-Whelan 1 (PW 1), which is located far away in the Galactic Halo (D≃ 29 kpc, Z≃ 15 kpc), and that is probably associated with the leading arm (LA) of the Magellanic Stream. We measure the systemic radial velocity of PW 1, Vr = 275 ± 10 km s−1, significantly larger than the velocity of the LA gas in the same direction. We re-discuss the main properties and the origin of this system in the light of these new observations, computing the orbit of the system and comparing its velocity with that of the H i in its surroundings. We show that the bulk of the gas at the velocity of the stars is more than 10 deg (5 kpc) away from PW 1 and the velocity difference between the gas and the stars becomes larger as gas closer to the stars is considered. We discuss the possibilities that (1) the parent gas cloud was dissolved by the interaction with the Galactic gas, and (2) that the parent cloud is the high-velocity cloud (HVC) 287.5+22.5 + 240, lagging behind the stellar system by ≃ 25 km s−1 and ≃10 deg ≃ 5 kpc. This HVC, which is part of the LA, has metallicity similar to PW 1, displays a strong magnetic field that should help to stabilize the cloud against ram pressure, and shows traces of molecular hydrogen. We also show that the system is constituted of three distinct pieces that do not differ only by position in the sky but also by stellar content.

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