时空胶囊 - 下篇 Time Capsules Part 2
上篇，我们了解了8个样本的筛选过程和质量，
接下来继续进行我们的探洞之旅，
看看它们能带给我们什么样的新发现！
Last time, we learned about the selection process and masses of the 8 samples, and now we'll continue our exploration to see
what new discoveries they can bring us!
探洞三部曲 之 速度
The Black Hole Trilogy - Velocity
知道了样本群和它们的质量，下一步就是计算他们的运动速度了。虽然他们可以从Hα发射线来获取数据，但最终的结果需要速度数据没有任何关于黑洞质量的信息，这样最后才能清楚得观察质量与速度的关系。因此，研究小组使用了Keck II级分光仪来测量了每个星系的Mg Ib射线，和部分的Ca II射线。
Now knowing the sample group and their masses, it’s time to find out the velocity dispersion. While it can be measured form the broad Hα emission lines, it is important to make sure these results are do not have traces information of the black hole masses. Therefore, for each of the 8, the group used the Keck II Echellette Spectrographer to measure the Mg Ib triplet and, where possible, the Ca II triplet.
只测量了部分Ca II射线是因为星系的红移经常会干扰Ca II波长。这也意味着只能使用Mg Ib的数据了。如果两个数据都可用，那么最终速度分散将使用Mg Ib和Ca II的平均值来计算。
Due the galaxies’ red shift, measurements of the Ca II wavelength are often contaminated, which means only the Mg Ib values can be used. If both values are available, then the overall velocity dispersion would be calculated used the mean on the Mg Ib and Ca II values.
图为来自太空望远镜科学研究所， 早期爱德文·哈勃在芝加哥大学的照片
Edwin Hubble at the University of Chicago, credit to the Space Telescope Science Institute
探洞三部曲 之 比较
The Black Hole Trilogy - Comparison
虽然8听起来不是一个很大的数字，但在M-σ色散关系中，研究小组的成果已经使矮星系的数量增加了一倍。结果显示，所有的AGN都位于分散图的低端，令人惊讶的是，它们都与其他天体的M-σ趋势表现非常相似。通过低质量黑洞这一点的确认，它帮助天文学家了解了直接与其宿主星系相互作用的黑洞质量新范围。它也进一步证明了一个事实，即矮星系中的黑洞的特点与其他星系的黑洞也非常相似。
Although 8 does not sound like a large number, the research of the group has doubled the number of dwarf galaxies in the M-σ dispersion relation. All the AGNs lie in the lower end of the dispersion and surprisingly, they all seem to be consistent with the trend for other stellar objects. By identifying these low mass black holes with close agreements with the overall relation, it has helped astronomers to extend their knowledge on the mass range of black holes that interact directly with their host galaxies. It also further evidences the fact that black holes in dwarf galaxies behave in similar ways to the others.
图为黑洞质量与星系的速度色散的关系，图中红色点为这次科学小组研究的8个对象
The black hole mass against the velocity dispersion of the galaxy, the red dots are the eight objects studied by the team
虽然这对于黑洞们说是令人兴奋的结果，但研究小组开始的目标是通过M-σ色散关系来研究更多关于黑洞是怎样在早期宇宙形成的。
Whilst this is exciting results for the black hole population, the group out set out to study more on how black holes masses can allow insight on the formation of them in the early universe.
不同的黑洞形成机制会对M-σ色散关系的结果产生不同的倾斜和排列分布。对于由早期III类恒星的坍缩形成的黑洞的预测是，它将产生较轻的黑洞，也就是说图中更陡的斜坡。另一方面，气体和尘埃的直接坍塌会产生较高质量黑洞，让M-σ线在图中显得更为平缓。
Different black hole seed formation mechanism would be reflected on the sloped and scatter of the results on the M-σ distribution. Prediction for the formation with stellar dominated collapse of lighter Population III ‘seeds’ would be a present-day population of under-massive black holes, meaning a steeper slope. On the other hand, heavier direct collapse would result in flattening of the M-σ distribution due to the higher masses.
遗憾的是，研究小组的8个黑洞都很好地符合了其他天体的M-σ，没有给出关于他们选择了哪条道路成为今天的自己的明确的答案。
Unfortunately, the fact that all 8 plots from the group fitted well with the plotted relationships, they did not give a definite answer on which path they took to become themselves today.
图为由NASA哈勃望远镜2011年拍到的名为Kinman的矮星系，也叫PHL 293B。2001 - 2011年之间，科学们在这个星系中发现了一颗巨大的恒星，但是在2011之后的研究中它便失踪了
The Kinman dwarf galaxy, also called PHL 293B, discover by NASA with Hubble. The picture was taken in 2011 before the disappearance of a massive star. Research on this galaxy started in 2001, during which scientists found signs of the star, however there were no signs of it again after 2011 until today.
然而，在信息有限的情况下，利用另一个质量比其他小得多的黑洞，以及他们使用的所有样本都是ANG的事实，小组仍然设法得出了一些结论。由于ANGs是高速吸附物质的黑洞，它们的质量和辐射会快速增加，研究小组可以假设探测到的ANG的质量都明显高于星系的其他部分。有趣的是，另一个质量很低的黑洞不是一个ANG，这意味着它可以更好地代表矮星系中的一般黑洞。
However, with the limited information, using another black hole with much lower mass compared to others and the fact that all the samples they used were all ANGs, the group did still manage to draw some conclusions. Since ANGs are black holes accreting materials at high rates, it would cause them to increase in mass and radiation. So, group made the assumption that the ANGs detected have significantly higher mass than the rest parts of the galaxy. And interestingly, the one other very low mass black hole is no an ANG, meaning it could be better representative of the general black holes in dwarf galaxies.
因此，如果以上假设是正确的话，那么ANG更有可能来自于恒星坍缩，而那个超轻黑洞代表了早期宇宙中黑洞形成的主要机制。
So, if the assumptions are correct, it would more likely that the ANGs came from stellar collapse and therefore the extreme light black hole represents the favored mechanism for black hole formation in the early universe.
虽然这是一种逻辑通顺的理解，但它仍然只是一种推测。在得出明确的结论之前，还需要对矮星系的黑洞进行更多的测量，来弄清这种超低质量一个例外还是一种常态。
While this can be a possible way in understanding the figures, it is still speculative. Before definite conclusions are made, much more measurements on the dwarf galaxy black holes need to be done to find out whether the extreme low was an exception or the normalcy.
所以，让我们就拭目以待未来的研究成果吧！
So, let's wait and see what the future brings us!
图为MPG/ESO 2.2米望远镜拍到的Carina矮星系，是离银河系最近的星系之一。虽然离我们很近，但由于它的低亮度和扩散度，很难被发现，1970年左右才第一次被观测到。科学家们认为这一类的星系应该很多，但因为过于’隐形‘，很难捕捉到他们的身影。
The Carina dwarf galaxy from the MPG/ESO 2.2m telescope. It is one of the closest galaxy to our Milky Way. Due to its dim and diffuse character, it was only discovered in the 1970s. Scientists believe there are many galaxies out there like this one, but their 'invisibleness' has made it extremely difficult to observe them.
图片来自 NASA-Sloan Atlas, NASA官网
部分信息参考来自耶鲁大学和蒙大拿州立大学的V F Baldassare, C Dickey, M Geha 和 A E Reines
的 “POPULATING THE LOW-MASS END OF THE MBH − σ∗ RELATION" 论文
Pictures from official website of NASA-Sloan Atlas, NASA.
*Parts are from “POPULATING THE LOW-MASS END OF THE MBH − σ∗ RELATION" by V F Baldassare, C Dickey, M Geha and A E Reines from Yale University and Montana State University
