编辑: 更新后的图，高分辨版本.
TA-DA!
这是一幅来自目前研究工作的初步图像。数据来自Milkyway@home分布式计算应用。
你看到的是人马座潮汐流位于银河系盘上的位置图。坐标系显示的是银河系的银经和银纬。银经沿着银河系盘增加，0度的位置在太阳附近，旋转方向从太阳往银河系中心，银纬是距离银盘的角度。（就像地图上的经度和纬度，只是太阳在坐标系中心，尺度为星系尺度。）颜色显示的是恒星数目的均方根（最终我们将采用实际星数来显示颜色）。关于银河系坐标可以参看维基解释，请 点击这里。
我们正在做的工作（这里的“我们”是指参与Milkyway@home项目的所有参与者）是利用统计模型来拟合斯隆数字化巡天的恒星数据，然后利用分离命令，将人马座潮汐流从银河系背景场星中分离出来。
人马座潮汐流是人马座矮星系的一部分，目前，人马座矮星系正在“坠入”银河系中，沿着坠入的整个轨道，银河系的潮汐力将星流中束缚松散的恒星剥离。经过一段时间，这些被剥离的恒星最终并入银河系。我们的银河系正在“吞并”人马座矮星系！实际上，处在银河系外围的很多恒星都是这样通过“互相蚕食”的方式而来的。
这幅图能够帮助我们理解银河系的质量分布，同时也能为大致理解星系形成历史提供线索。
(Sorry that I've been away for awhile - I recently recovered from a head injury that kept me out for a month, and I'm finally feeling back up to full strength!)
--Matthew N.
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As a side note: light from the stars in the Sagittarius Stream took between 50,000 and 130,000 YEARS for the light to reach us (depending on where along the stream you look)! That is, these stars are about that many light years away from us!
This does mean that the stream has had several thousand years to move before the light gets to us, but it is so massive and far away that hundreds of thousands of years are nothing to it. Streams this big and far away change on the order of ten of millions and billions of years! So we are pretty safe in saying that the stream still looks pretty much the same today.
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THANK YOU VERY MUCH!!!
Matthew it looks outstanding!!!
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Thanks for posting this. It's always interesting to see the actuall scientific results of all that crunching, it gives that "yeah, it was worth it" feeling.
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Sounds good, thx :)
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DSKAG Austria Research Team: http://www.research.dskag.at
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After looking half an hour on the map i got it. The b gave me trouble. But the closer the Sagittarius Tidal Debris Stream is, the higher you have to look up. It means it is above the galactic plane :)
Maybe someone will put your data into a plugin for Celestia (nice free 3d space simulator).
Dark matter, i hope it is there. In a recent study the didn't find as much as they thought. I would post the link to it, but it was one or two month ago and i didn't save it. Found it on portaltotheuniverse.org
I wonder what will become of the billions of possible stray planats zooming around in our galaxy. They can't be seen, so they are a kind of "Dark Matter" but not the Dark Matter which scientists search for.
Are there plans to simulate other galaxies to confirm your model works as observed? Andromeda, or some head on galaxies.
Well done, keep up the good work :)
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Excellent! It is interesting there is a star "hot spot" that is present on (I presume) the leading edge (direction of rotation) of the stream. What is interesting is that the hot spot is not on a the neutral axis of the stream, that is, it is to the outside. Is that because centripetal accelerations are high and pushing them towards the outside of the center line? I would expect the inside of the stream to have a high star density as it would be experiencing the same centripetal accelerations and shove all the stars together. Also, the stream tip should be artificially compacted as the leading edge of the stream is thinned out and elongated (much like a comet and tail).
It is curious that there is a low star density area on the inside of the steam as well as ahead of the steam. Are there other things at work I am missing or is the stream young in formation and hasn't had time to arrange itself as one would expect? Or, is it the very real possibility that I am wrong on all counts and expectations?
Glad you are ok. Thanks for the update; much appreciated.
Edit: I forgot to add the 3D component to the plot. So, the stream is not planar and curls so the low density "inside edge" as I referred to it, is actually behind the leading edge in terms of direction of travel. Therefore it seams the hot spot is acting like the comet center and everything else is the dust trail so to speak.
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Awesome!
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Amazing!
I Thank Thee, Matthew.
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Excellent! It is interesting there is a star "hot spot" that is present on (I presume) the leading edge (direction of rotation) of the stream. What is interesting is that the hot spot is not on a the neutral axis of the stream, that is, it is to the outside. Is that because centripetal accelerations are high and pushing them towards the outside of the center line? I would expect the inside of the stream to have a high star density as it would be experiencing the same centripetal accelerations and shove all the stars together. Also, the stream tip should be artificially compacted as the leading edge of the stream is thinned out and elongated (much like a comet and tail).
It is curious that there is a low star density area on the inside of the steam as well as ahead of the steam. Are there other things at work I am missing or is the stream young in formation and hasn't had time to arrange itself as one would expect? Or, is it the very real possibility that I am wrong on all counts and expectations?
The leading edge of the tidal stream is actually on the left side of the plot - the density increases (redder) as you approach the dwarf galaxy core. This is only the part of the stream that we have data for - so it cuts off on the right edge pretty noticeably.
The tidal stream actually wraps all the way around the galaxy, with "tails" in front and behind the Sagittarius dwarf galaxy - similar to a comet, if the comet also had a tail sticking out in front of it. This happens due to the "tidal" effects of our Milky Way Galaxy's gravitational pull.
James Bullock has some nice images of simulations that demonstrate this; I'll try to find more in the near future.
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