* Astronomy

Members Login
Post Info TOPIC: Magellanic Clouds


L

Posts: 130042
Date:
RE: Magellanic Clouds
Permalink  
 


Title: The four leading arms of the Magellanic Cloud system
Authors: M. S. Venzmer, J. Kerp, P. M. W. Kalberla

The Magellanic Cloud System (MCS) interacts via tidal and drag forces with the Milky Way galaxy. Using the Parkes Galactic All-Sky Survey (GASS) of atomic hydrogen we explore the role of drag on the evolution of the so-called Leading Arm (LA). We present a new image recognition algorithm that allows us to differentiate features within a 3-D data cube (longitude, latitude, radial velocity) and to parameterise individual coherent structures. We compiled an HI object catalogue of LA objects within an area of 70 degr x 85 degr (1.6 sr) of the LA region. This catalogue comprises information of location, column density, line width, shape and asymmetries of the individual LA objects above the 4-sigma threshold of Delta T_b simeq 200 mK. We present evidence of a fourth arm segment (LA4). For all LA objects we find an inverse correlation of velocities v_GSR in Galactic Standard of Rest frame with Magellanic longitude. High-mass objects tend to have higher radial velocities than low-mass ones. About 1/4 of all LA objects can be characterised as head-tail (HT) structures. Using image recognition with objective criteria, it is feasible to isolate most of LA emission from the diffuse Milky Way HI gas. Some blended gas components (we estimate 5%) escape detection, but we find a total gas content of the LA that is about 50% higher than previously assumed. These methods allow the deceleration of the LA clouds to be traced towards the Milky Way disk by drag forces. The derived velocity gradient strongly supports the assumption that the whole LA originates entirely in the Large Magellanic Cloud (LMC). LA4 is observed opposite to LA1, and we propose that both arms are related, spanning about 52kpc in space. HT structures trace drag forces even at tens of kpc altitudes above the Milky Way disk.

Read more (3186kb, PDF)



__________________


L

Posts: 130042
Date:
Permalink  
 

Herschel and Spitzer See Nearby Galaxies' Stardust

ssc2012-01b_Inline.jpg

The cold dust that builds blazing stars is revealed in new images that combine observations from the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions; and NASA's Spitzer Space Telescope. The new images map the dust in the galaxies known as the Large and Small Magellanic Clouds, two of the closest neighbours to our own Milky Way galaxy.
The Large Magellanic Cloud looks like a fiery, circular explosion in the combined Herschel-Spitzer infrared data. Ribbons of dust ripple through the galaxy, with significant fields of star formation noticeable in the center, center-left and top right (the brightest center-left region is called 30 Doradus, or the Tarantula Nebula, for its appearance in visible light). The Small Magellanic Cloud has a much more irregular shape. A stream of dust extends to the left in this image, known as the galaxy's "wing," and a bar of star formation appears on the right

Read more



__________________


L

Posts: 130042
Date:
Permalink  
 

Milky Way's Large Companion Galaxies Stand Out

Among the more than 20 satellite galaxies that hover around the Milky Way in a kind of galactic entourage are two large satellites known as the Large and Small Magellanic Clouds. Stargazers and navigators have known about them since before the age the telescope. Yet today's astrophysicists have had a hard time explaining how they got there. Computer simulations of galaxy formation and evolution tend not to produce bright satellite galaxies akin to the two Magellanic Clouds. So researchers had to ask: Are the simulations flawed - perhaps in the way that they account for the all-important role of the mysterious dark matter - or is the Milky Way just a bit of an oddball?
Read more



__________________


L

Posts: 130042
Date:
Permalink  
 

Title: Orbits of LMC/SMC with recent ground-based proper motions
Authors: Katerina Bartoskova, Bruno Jungwiert, Adam Ruzicka, Edgardo Costa

In recent years, with new ground-based and HST measurements of proper motions of the Magellanic Clouds being published, a need of a reanalysis of possible orbital history has arisen. As complementary to other studies, we present a partial examination of the parameter space -- aimed at exploring the uncertainties in the proper motions of both Clouds, taking into account the updated values of Galactic constants and Solar motion, which kinematically and dynamically influence the orbits of the satellites. In the chosen setup of the study, none of the binding scenarios of this pair could be neglected.

Read more (1263kb, PDF)



__________________


L

Posts: 130042
Date:
Permalink  
 

Giant cosmic tails point to a recent marriage

New models show that our nearest galactic neighbours became entangled in a cosmic dance over the past few billion years, with a dramatic close encounter around 1.2 billion years ago.
In a paper to be published in the Monthly Notices of the Royal Astronomical Society, International Centre for Radio Astronomy Research (UWA) astronomers Jonathan Diaz and Dr Kenji Bekki have modelled the movement of the Large and Small Magellanic Clouds around the Milky Way and the structure of the gas that surrounds them.

Read more

__________________


L

Posts: 130042
Date:
Permalink  
 

Title: How Common are the Magellanic Clouds?
Authors: Lulu Liu, Brian F. Gerke, Risa H. Wechsler, Peter S. Behroozi, Michael T. Busha

We introduce a probabilistic approach to the problem of counting dwarf satellites around host galaxies in databases with limited redshift information. This technique is used to investigate the occurrence of satellites with luminosities similar to the Magellanic Clouds around hosts with properties similar to the Milky Way in the object catalogue of the Sloan Digital Sky Survey. Our analysis uses data from SDSS Data Release 7, selecting candidate Milky-Way-like hosts from the spectroscopic catalogue and candidate analogs of the Magellanic Clouds from the photometric catalogue. Our principal result is the probability for a Milky-Way-like galaxy to host N_{sat} close satellites with luminosities similar to the Magellanic Clouds. We find that 81 percent of galaxies like the Milky Way are have no such satellites within a radius of 150 kpc, 11 percent have one, and only 3.5 percent of hosts have two. The probabilities are robust to changes in host and satellite selection criteria, background-estimation technique, and survey depth. These results demonstrate that the Milky Way has significantly more satellites than a typical galaxy of its luminosity; this fact is useful for understanding the larger cosmological context of our home galaxy.

Read more (1550kb, PDF)

__________________


L

Posts: 130042
Date:
Permalink  
 

Lonely stars born on a bridge between galaxies

Most stars are gregarious, grouping together by the billions in galaxies like our Milky Way. Now evidence is mounting that stars may form in between galaxies.
Vanessa McBride at the University of Southampton in the UK and her colleagues looked at X-rays arriving from the space between two nearby galaxies, the Large and Small Magellanic clouds. The energy spectrum and periodic fluctuations of the X-rays, recorded by the INTEGRAL satellite, suggest they are coming from young binary star systems in which a neutron star is stealing matter from its massive companion.

Read more

__________________


L

Posts: 130042
Date:
Magellanic Stream
Permalink  
 


Giant Intergalactic Gas Stream Longer than Thought

A giant stream of gas flowing from neighbour galaxies around our own Milky Way is much longer and older than previously thought, astronomers have discovered. The new revelations provide a fresh insight on what started the gaseous intergalactic streamer.
The astronomers used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to fill important gaps in the picture of gas streaming outward from the Magellanic Clouds. The first evidence of such a flow, named the Magellanic Stream, was discovered more than 30 years ago, and subsequent observations added tantalizing suggestions that there was more. However, the earlier picture showed gaps that left unanswered whether this other gas was part of the same system.

Read more

Image5.jpg
Expand (877kb, 2000 x 1000)
CREDIT: Nidever, et al., NRAO/AUI/NSF and Meilinger, Leiden-Argentine-Bonn Survey, Parkes Observatory, Westerbork Observatory, Arecibo Observatory.


Combined radio/optical image shows Milky Way, Magellanic Clouds, and the new radio image of the Magellanic Stream. Blue and white are the Milky Way and Magellanic Clouds. Red is the hydrogen gas in the Magellanic Stream, in the disks of the Magellanic Clouds, and in the stream's Leading Arm. The Milky Way is horizontal in the middle of the image; the Magellanic Clouds are the light spots at the center-right portion of the image, from which the gas stream originates. Brown is dust clouds in the Milky Way

__________________


L

Posts: 130042
Date:
RE: Magellanic Clouds
Permalink  
 


THE MAGELLANIC GROUP AND ITS SEVEN DWARF GALAXIES
Astronomers at the University of Zurich have proposed a new theory for the formation of dwarf galaxies. In a paper published in "The Astrophysical Journal", Elena D'Onghia and George Lake solve several outstanding problems by comparing observed dwarfs to supercomputer simulations of their formation (Astrophysical Journal Letters, Volume 686, Nr. 2, p. L61).
The properties of dwarf galaxies have presented many challenges.

"Ten years ago, my team at the University of Washington found that our cosmological model predicts 30-50 times as many small objects as we see. If the numbers had been nearly equal, that would have been an easy success for the model. If there were none, we might figure out a way to keep any from forming, but at the risk of confusing fairy tales, having 30-50 times fewer dwarfs than predicted presents a 'Goldilock's problem'. How do we keep most of them from forming, but not all?" - George Lake, lead author.

Read more

__________________


L

Posts: 130042
Date:
Permalink  
 

Title: Line of sight depth of the Large and Small Magellanic Clouds
Authors: Annapurni Subramaniam, Smitha Subramanian (Indian Institute of Astrophysics)

We used the red clump stars from the Optical Gravitational Lensing Experiment (OGLE II) survey and the the Magellanic Cloud Photometric Survey (MCPS), to estimate the line of sight depth. The observed dispersion in the magnitude and colour distribution of red clump stars is used to estimate the line of sight depth, after correcting for the contribution due to other effects. This dispersion due to depth, has a range from minimum dispersion that can be estimated, to 0.46 mag (a depth of 500 pc to 10.44 Kpc), in the LMC. In the case of SMC, the dispersion ranges from minimum dispersion to 0.35 magnitude (a depth of 665 pc to 9.53 Kpc). The thickness profile of LMC bar indicates that it is flared. The average depth in the bar region is 4.01.4 kpc. The halo of the LMC (using RR Lyrea stars) is found to have larger depth compared to the disk/bar, which supports the presence of inner halo for the LMC. The large depth estimated for the LMC bar and the disk suggests that the LMC might have had minor mergers. In the case of SMC, the bar depth (4.901.23 Kpc) and the disk depth (4.231.48 Kpc) are found to be within the standard deviations. We find evidence for increase in depth near the optical centre (up to 9 kpc). On the other hand, the estimated depth for the halo (RR Lyrea stars) and disk (RC stars) for the bar region of the SMC is found to be similar. Thus, increased depth and enhanced stellar as well as HI density near the optical centre suggests that the SMC may have a bulge.

Read more (79kb, PDF)

__________________
«First  <  1 2 3  >  Last»  | Page of 3  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard