예기치 않은 이중 퀘이사가 발견되었습니다. 충돌 과정에서 블랙홀을 점화하는 병합 은하 한 쌍

병합된 한 쌍의 은하가 충돌 과정에서 블랙홀을 점화

퀘이사는 우주에서 가장 밝은 천체 중 하나입니다. 하늘에 흩어져 1000억 개가 넘는 별의 풍요로움으로 빛나고 있습니다. 그리고 7월 4일의 밝은 대기 플레어처럼 우주 시간 척도에서 상대적으로 짧은 시간 동안 빛납니다. 그것은 고온으로 가열되는 많은 가스와 먼지를 삼키는 초대형 블랙홀에 의해 구동되기 때문입니다. 그러나 퀘이사 음식 뷔페는 너무 오래 지속됩니다.

퀘이사의 이 덧없는 속성은 천문학자들이 서로 충돌 경로에 있는 두 개의 퀘이사를 찾는 데 도움이 되었습니다. 그것은 100억년 전에 서로 충돌한 한 쌍의 은하에 내장되어 있습니다. 머나먼 우주에서 이렇게 다이나믹한 듀오는 보기 드물다. 이 발견은 오래 전에 은하들이 자주 충돌하고 블랙홀이 잔해와 제트에 삼켜졌을 때 우주가 얼마나 불안정했는지에 대한 단서를 제공합니다.

두 개의 퀘이사는 연료 양초의 유입이 감소함에 따라 서로 다른 속도로 깜박이기 때문에 우주에서 발생하는 비정상적인 활동으로 식별되었습니다. Hubble은 호스트 은하와 마찬가지로 이미지를 확대하고 명확하게 해결했습니다.

허블우주망원경이 촬영한 우주의 나이가 겨우 30억년에 불과했을 때 존재했던 한 쌍의 퀘이사. 충돌하는 한 쌍의 은하에 내장되어 있습니다. 퀘이사는 하나의 은하보다 작은 크기로 분리되어 있습니다. 퀘이사는 가스, 먼지 및 중력 범위 내에 있는 모든 것에 질식하면서 사나운 에너지 분수에서 분출하는 사나운 초대질량 블랙홀을 통과합니다. 블랙홀은 결국 병합됩니다. 출처: NASA, ESA, Yu-Ching Chen(UIUC), Hsiang-Chih Huang(IAS), Nadja Zakamska(JHU), Yu Chen(UIUC)

허블 우주망원경, 머나먼 우주에서 예기치 않게 이중 퀘이사 발견

초기 우주는 은하들이 서로 충돌하고 병합되기까지 하는 불안정한 장소였습니다. 사용[{” attribute=””>NASA’s Hubble Space Telescope and other space and ground-based observatories, astronomers investigating these developments have made an unexpected and rare discovery: a pair of gravitationally bound quasars, both blazing away inside two merging galaxies. They existed when the universe was just 3 billion years old.

Quasars are bright objects powered by voracious, supermassive black holes blasting out ferocious fountains of energy as they engorge themselves on gas, dust, and anything else within their gravitational grasp.

“We don’t see a lot of double quasars at this early time in the universe. And that’s why this discovery is so exciting,” said graduate student Yu-Ching Chen of the University of Illinois at Urbana-Champaign, lead author of this study.

Finding close binary quasars is a relatively new area of research that has just developed in the past 10 to 15 years. Today’s powerful new observatories have allowed astronomers to identify instances where two quasars are active at the same time and are close enough that they will eventually merge. 

There is increasing evidence that large galaxies are built up through mergers. Smaller systems come together to form bigger systems and ever larger structures. During that process there should be pairs of supermassive black holes formed within the merging galaxies. “Knowing about the progenitor population of black holes will eventually tell us about the emergence of supermassive black holes in the early universe, and how frequent those mergers could be,” said Chen.

This compass image shows a Hubble Space Telescope photograph of a pair of quasars that existed when the universe was just 3 billion years old. They are embedded inside a pair of colliding galaxies. The quasars are separated by less than the size of a single galaxy. Quasars are powered by voracious, supermassive black holes blasting out ferocious fountains of energy as they engorge themselves on gas, dust, and anything else within their gravitational grasp. The black holes will eventually merge. Credit: NASA, ESA, Yu-Ching Chen (UIUC), Hsiang-Chih Hwang (IAS), Nadia Zakamska (JHU), Yue Shen (UIUC)

We’re starting to unveil this tip of the iceberg of the early binary quasar population,” said Xin Liu of the University of Illinois at Urbana-Champaign. “This is the uniqueness of this study. It is actually telling us that this population exists, and now we have a method to identify double quasars that are separated by less than the size of a single galaxy.”

This was a needle-in-haystack search that required the combined power of NASA’s Hubble Space Telescope and the W.M. Keck Observatories in Hawaii. Multi-wavelength observations from the International Gemini Observatory in Hawaii, NSF’s Karl G. Jansky Very Large Array in New Mexico, and NASA’s Chandra X-ray Observatory also contributed to understanding the dynamic duo. And, ESA (European Space Agency)’s Gaia space observatory helped identify this double quasar in the first place. 

“Hubble’s sensitivity and resolution provided pictures that allow us to rule out other possibilities for what we are seeing,” said Chen. Hubble shows, unequivocally, that this is indeed a genuine pair of supermassive black holes, rather than two images of the same quasar created by a foreground gravitational lens. And, Hubble shows a tidal feature from the merging of two galaxies, where gravity distorts the shape of the galaxies forming two tails of stars.

However, Hubble’s sharp resolution alone isn’t good enough to go looking for these dual light beacons. The researchers enlisted Gaia, which launched in 2013, to pinpoint potential double-quasar candidates. Gaia measures the positions, distances, and motions of nearby celestial objects very precisely. But in a novel technique, it can be used to explore the distant universe. Gaia’s huge database can be used to search for quasars that mimic the apparent motion of nearby stars. The quasars appear as single objects in the Gaia data because they are so close together. However, Gaia can pick up a subtle, unexpected “jiggle” that mimics an apparent change in position of some of the quasars it observes. 

In reality, the quasars aren’t moving through space in any measurable way. Instead, their jiggle could be evidence of random fluctuations of light as each member of the quasar pair varies in brightness on timescales of days to months, depending on their black hole’s feeding schedule. This alternating brightness between the quasar pair is similar to seeing a railroad crossing signal from a distance. As the lights on both sides of the stationary signal alternately flash, the sign gives the illusion of “jiggling.”

Another challenge is that because gravity warps space like a funhouse mirror, a foreground galaxy could split the image of a distant quasar into two, creating the illusion it was really a binary pair. The Keck telescope was used to make sure there was no lensing galaxy in between us and the suspected double quasar.

Because Hubble peers into the distant past, this double quasar no longer exists. Over the intervening 10 billion years, their host galaxies have likely settled into a giant elliptical galaxy, like the ones seen in the local universe today. And, the quasars have merged to become a gargantuan, supermassive black hole at its center. The nearby giant elliptical galaxy, M87, has a monstrous black hole weighing 6.5 billion times the mass of our Sun. Perhaps this black hole was grown from one or more galaxy mergers over the past billions of years.

The upcoming NASA Nancy Grace Roman Space Telescope, having the same visual acuity as Hubble, is ideal for binary quasar hunting. Hubble has been used to painstakingly take data for individual targets. But Roman’s very wide-angle infrared view of the universe is 200 times larger than Hubble’s. “A lot of quasars out there could be binary systems. The Roman telescope can do huge improvements in this research area,” said Liu.

The results will be published in the April 5 journal Nature.

Reference: “A close quasar pair in a disk–disk galaxy merger at z = 2.17” by Yu-Ching Chen, Xin Liu, Adi Foord, Yue Shen, Masamune Oguri, Nianyi Chen, Tiziana Di Matteo, Miguel Holgado, Hsiang-Chih Hwang and Nadia Zakamska, 5 April 2023, Nature.
DOI: 10.1038/s41586-023-05766-6

The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.