* Astronomy

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RE: Magellanic Clouds

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Herschel and Spitzer See Nearby Galaxies' Stardust

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
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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?
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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.

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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.
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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.

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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.
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Magellanic Stream

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RE: Magellanic Clouds

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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 4.0±1.4 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 (4.90±1.23 Kpc) and the disk depth (4.23±1.48 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.

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