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.

    天文學(xué)家可能用他們的關(guān)點(diǎn)已經(jīng)解決了宇宙“先有雞還是先有蛋”的問題，即銀河系和具有特大質(zhì)量的黑洞和星系哪個(gè)先存在？

    多年以來，研究人員獲悉，在黑洞附近驚人的輻射產(chǎn)生了其巨大的吸力，反過來也為形成恒星提供動(dòng)力的同時(shí)，浩瀚的星系也為黑洞提供物質(zhì),所以黑洞和星系必定有共同的進(jìn)化史。

    在設(shè)在新墨西哥州的美國國家射電天文臺工作的克里斯 卡里（Chris Carilli）說道：“看起來是先有黑洞。正在收集有關(guān)的證據(jù)”。卡里在美國天文學(xué)會(huì)第213次會(huì)議上向他的團(tuán)隊(duì)展示了他今天所取得的研究成果。

    先前對星系附近的研究表明在黑洞中心的質(zhì)量和星系中心的凸起物的質(zhì)量（緊緊包圍恒星的塊和氣體）存在一個(gè)有趣的關(guān)系。黑洞的質(zhì)量是周圍凸起物質(zhì)量的塊的大一千倍。

    無論黑洞的質(zhì)量是太陽質(zhì)量的幾百萬倍還是幾十億倍，星系的年齡和尺寸總是這個(gè)比例。

    加利福尼亞理工學(xué)院研究小組成員Dominik Riechers說道：“這個(gè)不變的比例表明黑洞和凸起物以某種相互關(guān)系影響著彼此的生長”。“在整個(gè)研究過程中都保持著他們的質(zhì)量比，哪一個(gè)行生長，或者是一起行長仍然是一個(gè)迷：。

    為了回答這個(gè)迷，Carilli, Riechers 和他們的小組成員在新墨西哥州用非常大的陣列無線電望遠(yuǎn)鏡和在法國用高原日布雷干涉計(jì)去探索宇宙的起源是在137億年以前，也是第一個(gè)星系形成的時(shí)間。

    來自馬克斯普朗克射電天文學(xué)研究所的研究小組成員Fabian Walter 說：“最后我們已經(jīng)能夠測量黑洞和在大爆炸后第一個(gè)十億年形成在幾個(gè)星系中凸起物的質(zhì)量，并且證據(jù)表明在早期的宇宙中這個(gè)不變的比例是近似或不能被保持”。“相對于凸起物來說，在這些早期的星系中的黑洞比在附近銀河系看到的要大得很多”。

    Walter對結(jié)果的看法是：“這意味著黑洞首先開始生長”。

    精確地演算黑洞和中心凸起物怎樣相互影響生長和凸起物怎樣最終比黑洞生長得快而變得比黑洞大，在接下來的研究仍是沒有得到解決。

    Riechers說：“我們不知道在哪種原理用于這里會(huì)有效？為什么有效？研究過程中一些觀念建立了質(zhì)量之間的‘標(biāo)準(zhǔn)’比例”。

    Carilli 說目前仍在生產(chǎn)的新型的望遠(yuǎn)鏡，包括擴(kuò)大非常大的陣列望遠(yuǎn)鏡和阿塔卡馬大型毫米/次毫米望遠(yuǎn)鏡是揭開這個(gè)秘密的關(guān)鍵工具。