Galaxy collisions dominate the local universe

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Although I may be repeating information (there is another thread talking about this but this thread is by far more interesting) I went a digged this thread because of this:<br /><br />Sagittarius Dwarf (Sgr)<br />From 1998<br />http://antwrp.gsfc.nasa.gov/apod/ap980216.html<br />Explanation: Our Galaxy is being invaded. Recent observations indicate that in the next 100 million years, the Sagittarius Dwarf galaxy will move though the disk of our own Milky Way Galaxy yet again . The Sagittarius Dwarf (Sgr), shown as the extended irregular shape below the Galactic Center, is the closest of 9 known small dwarf spheroidal galaxies that orbit our Galaxy. Don't worry, our Galaxy is not in danger, but no such assurances are issued for the Sagittarius Dwarf: the intense gravitational tidal forces might pull it apart. Oddly, however, Sgr's orbit indicates that is has been through our Galaxy several times before, and survived! One possibility is that Sgr contains a great deal of low-density dark matter that hold it together gravitationally during these collisions.<br /><br />From 2003<br />http://www.astro.virginia.edu/~mfs4n/sgr/<br />NEW MAP OF THE MILKY WAY SHOWS OUR GALAXY TO BE A CANNIBAL<br />Study Shows the Milky Way is Out to Lunch<br /><br />Chicken Little was right. The sky is falling.<br />Thousands of stars stripped from the nearby Sagittarius dwarf galaxy are streaming through our vicinity of the Milky Way galaxy, according to a new view of the local universe constructed by a team of astronomers from the University of Virginia and the University of Massachusetts.<br /><br />Using volumes of data from the Two-Micron All Sky Survey (2MASS), a major project to survey the sky in infrared light led by the University of Massachusetts, the astronomers are answering questions that have baffled scientists for decades and proving that our own Mil

 

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Continuing my post above there is much more on the subject:<br /><br />This was the preprint presented and accepted at the ApJ<br /><br />http://www.astro.virginia.edu/~mfs4n/sgr/preprint.pdf<br />The 2MASS database has been used to make the first all-sky map of the M giant populations of the Sagittarius dwarf spheroidal galaxy system. The present discussion provides the first relatively reddening-free description and analysis of the central regions of the dwarf, as well as extensive new information on the extended tail structure of tidally stripped stars. The latter is particularly useful for placing all previous studies of the Sgr system into a well defined context, and places the most stringent constraints yet on models of the disruption of Sgr in the Galactic potential.<br /><br />From 2004<br />http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v619n2/60408/brief/60408.abstract.html<br /><br />A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. III. Constraints on the Flattening of the Galactic Halo<br /><br />Kathryn V. Johnston ,1 David R. Law ,2,3 and Steven R. Majewski 3<br /><br />Received 2004 April 21; accepted 2004 October 8<br /><br />ABSTRACT<br /><br />M giants selected from the Two Micron All Sky Survey (2MASS) have been used to trace streams of tidal debris apparently associated with the Sagittarius dwarf spheroidal galaxy (Sgr) that entirely encircle the Galaxy. While the Sgr M giants are generally aligned with a single great circle on the sky, we measure a difference of 104 ± 26 between the mean orbital poles of the great circles that best fit debris leading and trailing Sgr, which can be attributed to the precession of Sgr's orbit over the range of phases explored by the data set. Simulations of the destruction of Sgr in potentials containing

 

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CONFIRMATION OF HALO SUBSTRUCTURE USING QUEST RR LYRAE <br />DATA: THE NEW VIRGO STELLAR STREAM(VSS)<br />(2006)<br /> <br />Virgo Stellar Stream<br /><br />The Virgo Stellar Stream (also known as Virgo Overdensity, Virgo Dwarf Galaxy, or Virgo super star cluster) is the proposed name for a stream of stars in the constellation of Virgo which was discovered in 2005.[1][2] The stream is thought to be the remains of a dwarf spheroidal galaxy that is in the process of merging with the Milky Way. It is the largest galaxy visible from the Earth, in terms of the area of the night sky covered.<br /><br />January 9, 2006<br />The Sloan Digital Sky Survey reveals a new Milky Way neighbor<br />WASHINGTON — A huge but very faint structure, containing hundreds of thousands of stars spread over an area nearly 5,000 times the size of a full moon, has been discovered and mapped by astronomers of the Sloan Digital Sky Survey (SDSS-II).<br />At an estimated distance of 30,000 light years (10 kiloparsecs) from Earth, the structure lies well within the confines of the Milky Way Galaxy. However, it does not follow any of Milky Way's three main components: a flattened disk of stars in which the sun resides, a bulge of stars at the center of the Galaxy and an extended, roughly spherical, stellar halo. Instead, the researchers believe that the most likely interpretation of the new structure is a dwarf galaxy that is merging into the Milky Way. The new dwarf galaxy is found toward the constellation Virgo.