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Post Info TOPIC: The Large Magellanic Cloud
Blobrana


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RE: The Large Magellanic Cloud
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Title: CO, HI, recent Spitzer SAGE results in the Large Magellanic Cloud
Authors: Yasuo Fukui

Formation of GMCs is one of the most crucial issues in galaxy evolution. I will compare CO and HI in the LMC in 3 dimensional space for the first time aiming at revealing the physical connection between GMCs and associated HI gas at a ~40 pc scale. The present major findings are 1) [total CO intensity] [total HI intensity]0.8 for the 110 GMCs, and 2) the HI intensity tends to increase with the evolution of GMCs. I argue that these findings are consistent with the growth of GMCs via HI accretion over a time scale of a few x 10 Myrs. I will also discuss the role of the background stellar gravity and the dynamical compression by supershells in formation of GMCs.

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Blobrana


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The Milky Way's two best-known companion galaxies are recent immigrants rather than the long-time neighbours they were thought to be, a new study suggests.
The Large and Small Magellanic Clouds are a pair of nearby dwarf galaxies once thought to have been in orbit around our galaxy for billions of years.
But that picture was shaken up in January 2007 when a team of astronomers announced new measurements of the pair's motion across the sky made by the Hubble Space Telescope.
Those observations suggested that the two galaxies are moving too fast to be long-time satellites of the Milky Way and instead are falling into our galactic neighbourhood for the first time.

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Blobrana


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The Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are two of the Milky Way's closest neighbouring galaxies. A stunning sight in the southern hemisphere, they were named after Ferdinand Magellan, who explored those waters in the 16th century. For hundreds of years, these galaxies were considered satellites of the Milky Way, gravitationally bound to our home galaxy. New research by Gurtina Besla (Harvard-Smithsonian Centre for Astrophysics) and her colleagues shows that the Magellanic Clouds are recent arrivals on their first visit to the Milky Way's neighbourhood.

"We have known about the Clouds since the time of Magellan, and a single measurement has thrown out everything we thought we understood about their history and evolution" - Gurtina Besla.

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Blobrana


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Title: Large Magellanic Cloud Distance from Cepheid Variables using Least Squares Solutions
Authors: C. Ngeow (UIUC), S. Kanbur (SUNY Oswego)

Distance to the Large Magellanic Cloud (LMC) is determined using the Cepheid variables in the LMC. We combine the individual LMC Cepheid distances obtained from the infrared surface brightness method and a dataset with a large number of LMC Cepheids. Using the standard least squares method, the LMC distance modulus can be found from the ZP offsets of these two samples. We have adopted both a linear P-L relation and a "broken"' P-L relation in our calculations. The resulting LMC distance moduli are 18.48 ±0.03 mag and 18.49 ±0.04 mag (random error only), respectively, which are consistent to the adopted 18.50 mag in the literature.

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Blobrana


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NGC 1783
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Title: The intermediate-age globular cluster NGC 1783 in the Large Magellanic Cloud
Authors: A. Mucciarelli (1), L. Origlia (2), F. R. Ferraro (1) ((1) Dipartimento di Astronomia, Universita' di Bologna, Italy, (2) INAF - Osservatorio Astronomico di Bologna, Italy)

We present Hubble Space Telescope ACS deep photometry of the intermediate-age globular cluster NGC 1783 in the Large Magellanic Cloud. By using this photometric dataset, we have determined the degree of ellipticity of the cluster (epsilon=0.14 ±0.03) and the radial density profile. This profile is well reproduced by a standard King model with an extended core (r_c=24.5'') and a low concentration (c=1.16), indicating that the cluster has not experienced the collapse of the core.
We also derived the cluster age, by using the Pisa Evolutionary Library (PEL) isochrones, with three different amount of overshooting (namely, Lambda_{os}=0.0, 0.10 and 0.25). From the comparison of the observed Colour-Magnitude Diagram (CMD) and Main Sequence (MS) Luminosity Function (LF) with the theoretical isochrones and LFs, we find that only models with the inclusion of some overshooting (Lambda_{os}=0.10-0.25) are able to reproduce the observables. By using the magnitude difference delta V_{SGB}^{He-Cl}=0.90 between the mean level of the He-clump and the flat region of the SGB, we derive an age tau=1.4 ±0.2 Gyr.

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Blobrana


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RE: The Large Magellanic Cloud
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Title: HST's view of the youngest massive stars in the Magellanic Clouds
Authors: M. Heydari-Malayeri (1), M.R. Rosa (2), V. Charmandaris (3 and 1), L. Deharveng (4), F. Martins (5), F. Meynadier (1), D. Schaerer (6), H. Zinnecker (7) ((1) LERMA, Paris Observatory, France, (2) ST-ECF, ESO, Germany; affiliated to the Space Telescope Operations Division, RSSD, ESA, (3) University of Crete, Greece, (4) Marseille Observatory, France, (5) MPE, Garching bei Munchen, Germany, (6) Geneva Observatory, Switzerland; Observatoire Midi-Pyrenees, Laboratoire d`Astrophysique, Toulouse, France, (7) Potsdam Astrophysical Institute, Germany)

Accurate physical parameters of newborn massive stars are essential ingredients to shed light on their formation, which is still an unsolved problem. The rare class of compact H II regions in the Magellanic Clouds (MCs), termed ''high-excitation blobs'' (HEBs), presents a unique opportunity to acquire this information. These objects (~ 4" to 10", ~ 1 to 3 pc, in diameter) harbour the youngest massive stars of the OB association/molecular cloud complexes in the MCs accessible through high-resolution near-IR and optical techniques. We present a brief overview of the results obtained with HST mainly on two HEBs, one in the LMC (N159-5) and the other in the SMC (N81).

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Blobrana


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Title: Structure of the Periphery of the Large Magellanic Cloud Revealed by 2MASS
Authors: David R. Alves
(Version v2)

This paper has been withdrawn.

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Blobrana


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LH54-425
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LH54-425_sm
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This false-colour image from the Curtis Schmidt Telescope in Chile shows a large star-forming region in the Large Magellanic Cloud. The binary system LH54-425 is arrowed. It is located in the star cluster LH54.
Credit: Chris Smith and the University of Michigan Curtis Schmidt Telescope at CTIO.

"The merger of two massive stars to make a single super star of over 80 suns could lead to an object like Eta Carinae, which might have looked like LH54-425 one million years ago. Finding stars this massive so early in their life is very rare. These results expand our understanding of the nature of very massive binaries, which was not well understood. The system will eventually produce a very energetic supernova" - George Sonneborn.

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Using NASAs Far Ultraviolet Spectroscopic Explorer (FUSE) satellite and ground-based telescopes, astronomers have determined, for the first time, the properties of a rare, extremely massive, and young binary star system.
The system, known as LH54-425, is located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The binary consists of two O-stars, the most massive and luminous types of stars in the Universe.
Spectra obtained by Georgia State University astronomer Stephen Williams at the 1.5-meter (4.9 foot) telescope at the Cerro Tololo Inter-American Observatory in Chile show that the two stars contain about 62 and 37 times the mass of our Sun. The stars are so close to each other -- about one-sixth the average Earth-Sun distance -- that they orbit around a common centre of mass every 2.25 days, says Williams colleague Douglas Gies of Georgia State University, Atlanta. With a combined mass of about 100 suns, the system is one the most extreme binaries known. The stars are probably less than 3 million years old.

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Blobrana


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RE: The Large Magellanic Cloud
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Title: Topology of HI in the Large Magellanic Cloud
Authors: S. Kim, C. Park
(version v2)

We have analysed the HI aperture synthesis image of the Large Magellanic Cloud (LMC), using an objective and quantitative measure of topology to understand the HI distribution hosting a number of holes and clumps of various sizes in the medium. The HI distribution shows different topology at four different chosen scales. At the smallest scales explored (19-29 pc), the HI mass is distributed in such a way that numerous clumps are embedded on top of a low density background. At the larger scales from 73 to 194 pc, it shows a generic hole topology. These holes might have been formed mainly by stellar winds from hot stars. At the scales from 240 to 340 pc, slightly above the disk scale-height of the gaseous disk, major clumps in the HI map change the distribution to have a slight clump topology. These clumps include the giant cloud associations in the spiral arms and the thick filaments surrounding superholes. At the largest scales studied (390-485 pc), the hole topology is present again. Responsible to the hole topology at this scale are a few superholes which seem mainly associated with supernova explosions in the outer disk. The gaps between the bar and spiral arms have a minor effect on the topology at this scale.

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