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Scientists Determine Large Magellanic Cloud Galaxy Formed Similar To Milky Way
Science Daily/University Of California - Berkeley ^ | 09/12/03 | Staff Writer

Posted on 09/12/2003 6:50:28 AM PDT by bedolido

LIVERMORE, Calif. -- An astronomer from the Lawrence Livermore National Laboratory, in collaboration with an international team of researchers, have discovered that a neighboring galaxy -- the Large Magellanic Cloud (LMC) -- appears to have formed with an old stellar halo, similar to how our very own Milky Way formed.

The oldest and most metal-poor Milky Way stars form a spherical halo where they move about like atoms in a hot gas, which in turn prompts two major formation scenarios of our galaxy: extended hierarchical accretion and rapid collapse. RR Lyrae stars, which are found both in the Milky Way and the LMC, are excellent tracers of old and metal-poor populations.

By measuring the movement of 43 RR Lyrae stars in the inner regions of the LMC, the team determined that a moving hot, metal-poor, old halo also exists in the LMC, suggesting that the Milky Way and smaller, more irregular galaxies like the LMC have similar early formation histories.

The research, titled "Kinematic Evidence for an Old Stellar Halo in the Large Magellanic Cloud," is featured in the Sept. 12 issue of Science.

Kem Cook of Livermore's Institute of Geophysics and Planetary Physics and part of the Massive Compact Halo Objects (MACHO) team, which previously discovered the RR Lyrae stars in the LMC, noted that they are an easily identified tracer of an old, metal-poor population. The LMC is more than 160,000 light-years away from our galaxy.

"The bottom line is that the Large Magellanic Cloud seems to have had a similar early formation history as the Milky Way," Cook said. "It created a spherical component that is not rotationally supported, but the stars have high random velocities, like a hot gas."

Cook, along with scientists from Universidad Pontifica Catolica in Chile, the European Southern Observatory, Columbia Astrophysics Laboratory and the Mount Stromlo Observatory at The Australian National University, observed the LMC RR Lyrae stars in January 2003 and measured the radial velocity dispersion using the European Southern Obervatories VLT.

The large-velocity dispersion of the LMC RR Lyrae stars scales to the Milky Way RR Lyrae star's velocity dispersion and indicates that metal-poor old stars in the LMC are distributed in a halo population.

Models of halo formation by accretion indicate that these old objects formed in small satellite galaxies that were subsequently accreted (eaten up) by the galaxy. Meanwhile, models of halo formation by dissipational collapse indicate that the halo formed rapidly before the disk collapsed. The researchers applied these models to smaller galaxies and observed a halo population in the LMC by its oldest objects.

Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy's National Nuclear Security Administration.

--------------------------------------------------------------------------------

This story has been adapted from a news release issued by University Of California - Berkeley.


TOPICS: Astronomy
KEYWORDS: crevolist

1 posted on 09/12/2003 6:50:30 AM PDT by bedolido
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To: bedolido

2 posted on 09/12/2003 6:52:43 AM PDT by bedolido (I can forgive you for killing my sons, but I cannot forgive you for forcing me to kill your sons)
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To: BMCDA; CobaltBlue; Condorman; Dimensio; Doctor Stochastic; donh; general_re; Gumlegs; Ichneumon; ...
Science Ping.
3 posted on 09/12/2003 12:33:43 PM PDT by balrog666 (Calling Atheism a religion is like calling bald a hair color. -Don Hirschberg)
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To: bedolido
Cool! Thanks for posting this, would have never seen it otherwise! This is exciting news for all of the galactic dynamicists out there. It provides a possible upper limit for the closest approach distance, as well as the earliest capture time of the LMC in prior orbits. Pretty neat stuff.
4 posted on 09/12/2003 12:36:24 PM PDT by ThinkPlease (Fortune Favors the Bold!)
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To: VadeRetro; jennyp; Junior; longshadow; *crevo_list; RadioAstronomer; Scully; Piltdown_Woman; ...
Some overlapping pings. [This ping list is for the evolution side of evolution threads, and sometimes for other science topics. FReepmail me to be added or dropped.]
5 posted on 09/12/2003 12:45:19 PM PDT by PatrickHenry
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To: balrog666

6 posted on 09/12/2003 1:14:09 PM PDT by js1138
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To: balrog666
I spent a lot of childhood time thinking about becoming a radio astronomer because of this book. Fortunately I didn't because there is already a RadioAstronomer.
7 posted on 09/12/2003 1:16:40 PM PDT by js1138
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To: js1138
Hoyle shoulda stayed with astronomy, instead of getting himself all messed up with that "tornado in a junkyard" nonsense. Even as a steady-stater, he would have had a lot more prestige. "A man's gotta know his limitations."
8 posted on 09/12/2003 1:54:15 PM PDT by PatrickHenry
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To: js1138; RadioAstronomer
Ah, there can't be enough RadioAstronomers ;)
9 posted on 09/12/2003 1:55:26 PM PDT by BMCDA
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To: BMCDA
Too bad there's only one.
10 posted on 09/12/2003 1:56:11 PM PDT by js1138
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To: PatrickHenry
Speaking of junkyards, how'd this thread wind up in the junkyard?
11 posted on 09/12/2003 1:57:14 PM PDT by js1138
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To: js1138
Too bad there's only one.

Indeed ;)
I also thought about becoming one in my childhood but well, as you might have guessed I didn't pursue this career.

12 posted on 09/12/2003 2:02:57 PM PDT by BMCDA
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To: js1138
It's not. Not yet, anyway.
13 posted on 09/12/2003 2:03:05 PM PDT by PatrickHenry
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To: balrog666
Thanks for the heads up!
14 posted on 09/12/2003 8:50:27 PM PDT by Alamo-Girl
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To: bedolido
I'd read somewhere that the LMC shows vestiges of spiral structure. Its passages too close to our galaxy may have distorted it. Hmmm...

Here's the LMC's biggest star-forming region, the Tarantula Nebula.


15 posted on 09/12/2003 10:39:09 PM PDT by petuniasevan (Interstate highways in Hawaii - HUH?)
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To: BMCDA; js1138
Ah, there can't be enough RadioAstronomers ;)

Too bad there's only one

Naw! There are gobs of them! :-)

16 posted on 09/15/2003 8:41:32 PM PDT by RadioAstronomer
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To: bedolido
Thanks for the post. :-)
17 posted on 09/15/2003 8:42:02 PM PDT by RadioAstronomer
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To: PatrickHenry
And thanks for the ping :-)
18 posted on 09/15/2003 8:42:23 PM PDT by RadioAstronomer
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To: js1138; balrog666
Fortunately I didn't because there is already a RadioAstronomer.

Hehehe! :-)))

19 posted on 09/15/2003 8:43:15 PM PDT by RadioAstronomer
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