手机版
Astronomers may have solved a cosmic chicken-and-the-egg problem: Which came first — galaxies or the supermassive black holes in their cores?
For several years now, researchers have known that galaxies and black holes must have co-evolved, with budding galaxies feeding material to a growing black hole while the immense gravity of the black hole generated in its vicinity tremendous radiation that in turn powered star formation. But the scientists hadn't pegged the starting point.
"It looks like black holes came first. The evidence is piling up," said Chris Carilli of the National Radio Astronomy Observatory in New Mexico. Carilli presented his team's findings here today at the 213th meeting of the American Astronomical Society.
Previous studies of nearby galaxies revealed an intriguing link between the masses of the black holes at their centers and the mass of the central "bulge" (a mass of tightly packed stars and gas) in the galaxies: The black hole's mass is always about one one-thousandth the mass of the surrounding bulge.
The ratio is the same for galaxies of all ages and sizes, whether the central black hole is a few million or many billions of times the mass of our sun.
"This constant ratio indicates that the black hole and the bulge affect each others' growth in some sort of interactive relationship," said study team member Dominik Riechers of Caltech. "The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process."
To help answer this question, Carilli, Riechers and the rest of their team used the Very Large Array radio telescope in New Mexico and the Plateau de Bure Interferometer in France to peer back to near the beginning of the universe, thought to be 13.7 billion years ago, when the first galaxies were forming.
"We finally have been able to measure black-hole and bulge masses in several galaxies seen as they were in the first billion years after the Big Bang, and the evidence suggests that the constant ratio seen nearby may not hold in the early universe," said study team member Fabian Walter of the Max-Planck Institute for Radioastronomy in Germany. "The black holes in these young galaxies are much more massive compared to the bulges than those seen in the nearby universe."
The upshot: "The implication is that the black holes started growing first," Walter said.
The next piece to place in the puzzle will be to figure out exactly how black holes and central bulges affect each others' growth and how the bulges eventually race past the black holes to become more massive.
"We don't know what mechanism is at work here, and why, at some point in the process, the 'standard' ratio between the masses is established," Riechers said.
New telescopes currently in the works, including the Expanded Very Large Array and the Atacama Large Millimeter/Submillimeter Array, will be key tools in solving this mystery, Carilli said.
天文学家可能用他们的关点已经解决了宇宙“先有鸡还是先有蛋”的问题，即银河系和具有特大质量的黑洞和星系哪个先存在？
多年以来，研究人员获悉，在黑洞附近惊人的辐射产生了其巨大的吸力，反过来也为形成恒星提供动力的同时，浩瀚的星系也为黑洞提供物质,所以黑洞和星系必定有共同的进化史。
在设在新墨西哥州的美国国家射电天文台工作的克里斯 卡里（Chris Carilli）说道：“看起来是先有黑洞。正在收集有关的证据”。卡里在美国天文学会第213次会议上向他的团队展示了他今天所取得的研究成果。
先前对星系附近的研究表明在黑洞中心的质量和星系中心的凸起物的质量（紧紧包围恒星的块和气体）存在一个有趣的关系。黑洞的质量是周围凸起物质量的块的大一千倍。
无论黑洞的质量是太阳质量的几百万倍还是几十亿倍，星系的年龄和尺寸总是这个比例。
加利福尼亚理工学院研究小组成员Dominik Riechers说道：“这个不变的比例表明黑洞和凸起物以某种相互关系影响着彼此的生长”。“在整个研究过程中都保持着他们的质量比，哪一个行生长，或者是一起行长仍然是一个迷：。
为了回答这个迷，Carilli, Riechers 和他们的小组成员在新墨西哥州用非常大的阵列无线电望远镜和在法国用高原日布雷干涉计去探索宇宙的起源是在137亿年以前，也是第一个星系形成的时间。
来自马克斯普朗克射电天文学研究所的研究小组成员Fabian Walter 说：“最后我们已经能够测量黑洞和在大爆炸后第一个十亿年形成在几个星系中凸起物的质量，并且证据表明在早期的宇宙中这个不变的比例是近似或不能被保持”。“相对于凸起物来说，在这些早期的星系中的黑洞比在附近银河系看到的要大得很多”。
Walter对结果的看法是：“这意味着黑洞首先开始生长”。
精确地演算黑洞和中心凸起物怎样相互影响生长和凸起物怎样最终比黑洞生长得快而变得比黑洞大，在接下来的研究仍是没有得到解决。
Riechers说：“我们不知道在哪种原理用于这里会有效？为什么有效？研究过程中一些观念建立了质量之间的‘标准’比例”。
Carilli 说目前仍在生产的新型的望远镜，包括扩大非常大的阵列望远镜和阿塔卡马大型毫米/次毫米望远镜是揭开这个秘密的关键工具。
