Dusty, compact object connecting galaxies and quasars at the cosmic dawn

(ORDO NEWS) — An international team of astrophysicists led by the Niels Bohr Institute, the University of Copenhagen and the Technical University of Denmark have identified a distant object whose properties are between those of a galaxy and a so-called quasar.

The object can be seen as the ancestor of a supermassive black hole, and was born relatively soon after the Big Bang. Modeling has shown that such objects must exist, but this is the first actual discovery.

“The detected object connects two rare populations of celestial objects, namely dusty stellar outbursts and glowing quasars, and thus opens up a new path to understanding the rapid growth of supermassive black holes in the early universe,” says Seiji Fujimoto, a postdoctoral fellow at the Niels Bohr Institute at the University of Copenhagen.

The discovery can be attributed to the Hubble Space Telescope, which is jointly operated by ESA and NASA. Due to its location in space, the telescope can look further into the depths of the universe than would be possible on earth.

And in astronomy, being able to look further means being able to observe phenomena that happened in earlier cosmic periods, since light and other forms of radiation travel a longer distance to reach us.

The newly found object, named by the GNz7q team, was born 750 million years after the Big Bang, which is considered to be the beginning of the Universe as we know it. Since the Big Bang happened about 13.8 billion years ago, GNz7q originated in an era known as “cosmic dawn”.

The mystery of supermassive black holes

The discovery is associated with a certain type of quasars. Quasars, also known as quasi-stellar objects, are extremely luminous objects. Images from Hubble and other modern telescopes have shown that quasars originate at the centers of galaxies.

The host galaxy GNz7q is an intensely star-forming galaxy, forming stars at a rate 1600 times faster than our own Milky Way galaxy.

The stars, in turn, create and heat cosmic dust, causing it to glow in the infrared to such an extent that the dust emission host GNz7q glows brighter than any other known object during this period of cosmic dawn.

In recent years, it has become clear that luminous quasars are powered by supermassive black holes with masses ranging from millions to tens of billions of solar masses, surrounded by huge amounts of gas. As the gas falls towards the black hole, it heats up due to friction, which provides a huge glowing effect.

“Understanding how supermassive black holes form and grow in the early universe has become a major mystery.

Theorists predicted that these black holes go through an early phase of rapid growth: a compact object emerges from a heavily dusty stellar galaxy, then transitions into a non-dusty luminous compact object by ejection ambient gas and dust,” explains Associate Professor Gabriel Brammer, Niels Bohr Institute.

“Although luminous quasars have already been detected even in the earliest epochs of the existence of the Universe, the transitional phase of rapid growth of both a black hole and its stellar flare carrier has not been detected in similar epochs.

Moreover, the observed properties are in agreement with theoretical modeling and allow suggest that GNz7q is the first example of a transitional phase of rapid black hole growth in the core of a dusty star, an ancestor of later supermassive black holes.”

Hide and seek in plain sight

Curiously, GNz7q was found in the center of a heavily studied field of sky known as the Hubble GOODS North Field.

“It shows how often great discoveries can be hidden right in front of you,” says Gabriel Brammer.

The discovery of GNz7q in public view was only made possible by the uniquely detailed, multi-wavelength data available to GOODS North. Without such a wealth of data, the object would be easy to miss, as it lacks the distinctive features of quasars in the early universe.

“It’s unlikely that the discovery of GNz7q in the relatively small GOODS-N study was just ‘stupid luck’; rather, the abundance of such sources could be significantly higher than previously thought,” Brammer adds.

The team now hopes to systematically search for such objects using dedicated high-resolution surveys and take advantage of the NASA/ESA/CSA James Webb Space Telescope.

A full characterization of these objects and a more detailed study of their evolution and physics will be made possible by the James Webb Telescope. Once regular work begins, Webb will be able to determine how common these rapidly growing black holes are,” says Seiji Fujimoto.

GNz7q discovery article “Dusty Compact Object Connecting Galaxies and Quasars at Cosmic Dawn” published in Nature April 13, 2022 .

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