Webb reveals black hole that formed before its galaxy
Webb reveals black hole that formed before its galaxy
The first direct mass measurement from the early Universe weighs in on the debate over the origins of supermassive black holes.
Using the unprecedented imaging and spectroscopic power of the NASA/ESA/CSA James Webb Space Telescope, researchers have mapped the motion and composition of gas orbiting a black hole in the centre of Abell2744-QSO1, a tiny galaxy more than 13 billion light-years away. The results suggest that the 50-million-solar-mass black hole predates its host galaxy, possibly forming within the first second of the Big Bang, and must have been immense from the start.
Which comes first, the galaxy or the black hole? Scientists have long thought it could be the galaxy: large stars within an existing galaxy consume their fuel and collapse to form black holes, which can gobble up surrounding material and merge over time to form more massive entities. But it’s hard to figure out how black holes millions to billions of times the mass of the Sun, thousands of which have now been detected in the early Universe, could have grown so quickly from such small seeds.
Now, researchers using Webb have detected clear evidence that some supermassive black holes were enormous from the beginning, forming without a stellar collapse phase, and without a significantly more massive host galaxy to feed them.
“This is a remarkable finding,” said Roberto Maiolino of Cambridge University in the United Kingdom, co-author of studies published today in Nature and the Monthly Notices of the Royal Astronomical Society. “It’s a paradigm shift, a total revisiting of the classical scenarios of how black holes form and grow.”
Little Red Dot QSO1
The team’s conclusion is based on detailed observations of Abell2744-QSO1 (QSO1), a prototypical Little Red Dot that existed just 700 million years after the Big Bang.
Although QSO1 is only 1,300 light-years across, and its light has been traveling for more than 13 billion years, it is easier to study than most other Little Red Dots because it is gravitationally lensed by galaxy cluster Abell 2744 (Pandora’s Cluster). QSO1 is both magnified and triply imaged, appearing in three different locations in the sky.
Initial studies of QSO1 revealed compelling evidence that it may be little more than a cloud of glowing hydrogen and helium gas circling a supermassive black hole estimated at 40 million times the mass of the Sun. But as with other early black holes discovered by Webb, there was uncertainty about whether it really was that massive.
“Before now, all of the mass measurements of black holes in the early Universe have been indirect, based on assumptions from what we know about them in the local Universe. We didn’t know if those assumptions really apply to the distant Universe,” said co-author Francesco D’Eugenio, also of Cambridge University.
Mapping gas composition, velocity
The team recognised that if QSO1’s black hole is as massive as it looks, they should be able to use the integral field unit (IFU) on Webb’s NIRSpec (Near Infrared Spectrograph) to trace the effects of its gravity on the gas swirling around it, while also mapping the distribution of various elements in the gas.
Cambridge graduate student Ignas Juodžbalis and Cosimo Marconcini of the University of Florence in Italy, lead authors on one of the studies, used the IFU observations to map motions of hydrogen gas surrounding the black hole. When they plotted the rotation velocity as a function of distance from the centre, they found that the gas has Keplerian motion: it orbits a central point in the same way that planets in our Solar System orbit the Sun.
“This is important because it tells us that most of the mass of QSO1 is concentrated in the black hole at the centre,” said Juodžbalis. “If the mass were more distributed, as it would be if there were a lot of stars, the gas would not have this perfect Keplerian rotation.
Since Keplerian motion is governed by simple laws of gravity, the team was able to use the gas velocity measurements to calculate the black hole mass directly, a feat that had not previously been possible. They found that not only is the black hole immense — roughly 50 million solar masses — it makes up an astonishing two-thirds of QSO1’s total mass. This proportion is thousands of times greater than in nearby galaxies, where supermassive black holes make up only a tiny fraction of the host galaxy’s total mass.
The IFU composition maps supported these results, showing that the gas throughout QSO1 is almost entirely hydrogen and helium, with very little of the heavier elements like oxygen that would be expected in a galaxy rich with stars and stellar debris. With a metallicity less than 0.5% of the Sun, QSO1 is one of the most pristine galactic environments ever measured.
“This is a phenomenal result,” said Maiolino. “It is the first direct measurement of a black hole mass within the first billion years after the Big Bang, and it is consistent with the previous measurements.” The team thinks this is a good sign that the assumptions used for indirect mass measurements are valid and the masses of other black holes in the early Universe have not been overestimated.
Supermassive black hole origins
The outsized mass of QSO1 relative to its host galaxy suggests that it can’t have formed gradually from much smaller, stellar-mass black holes merging and feeding. “It seems that we have found a black hole that does not have a substantial host galaxy and that has predated stellar processes,” said Juodžbalis. “This is very exciting because it is evidence for primordial black holes or direct collapse black holes, which have been theorised but not confirmed."
Whether QSO1’s black hole evolved from a “heavy seed” that formed within the first second of the Big Bang or somewhat later from the collapse of a giant cloud of gas, it was almost certainly born big, and may be in the early stages of building a galaxy around it.
The team thinks that Little Red Dots like QSO1 cannot have been rare in the early Universe, and is in the process of analysing similar objects to find out whether supermassive black holes actually do predate the galaxies where they currently reside.
Little Red Dot Abell2744-QSO1 (NIRCam Image)
This is an image from NIRCam (Near Infrared Camera) on Webb that shows Abell2744-QSO1, magnified and triply imaged by galaxy cluster Abell 2744.
Abell2744-QSO1 (QSO1) is a prototypical Little Red Dot, one of the first of hundreds of tiny glowing flecks of infrared light that Webb has found speckling the early Universe. QSO1 is roughly 1,300 light-years across and with a cosmological redshift (z) of 7, its light dates back to just 700 million years after the Big Bang, when the Universe was only 5% of its current age.
QSO1 is ideal for study because it is gravitationally lensed, both magnified and triply imaged by Abell 2744, the intervening mega-cluster of galaxies that warps its surrounding space-time.
Detailed study of the brightest of the three lensed images, QSO1A (upper right), shows that the object consists of a central supermassive black hole 50 million times the mass of the Sun, surrounded by a cloud of hydrogen and helium gas with very small amounts of heavier elements like oxygen. Unlike supermassive black holes in nearby galaxies, which make up only a tiny fraction of their host galaxy’s total mass, QSO1’s black hole contains twice as much mass as the galactic material surrounding it.
[Image description: Image showing hundreds of bright objects of different size, colour, and shape on the black background of space. Colours range from white to deep red. Shapes include elliptical, spiral, dot-like, dash-like, and arcuate.Three objects in the central part of the image are called out with small white boxes that contain images of the three objects. From top to bottom these are labeled QSO1A, QSO1B, and QSO1C. At the centre of each box is a tiny, circular red dot. QSO1A (top) is notably larger, brighter, and clearer than the other two. QSO1B, in the middle, is the smallest and fuzziest, and is somewhat washed out by the light of a larger white object next to it.]
Credit:NASA, ESA, CSA, L. Furtak (Ben-Gurion University), R. Maiolino (Cambridge), F. D'Eugenio (Cambridge), I. Juodžbalis (Cambridge), H. Übler (MPE), C. Marconcini (University of Florence). Image processing: A. Pagan
Little Red Dot Abell2744-QSO1a (NIRCam image with NIRSpec IFU velocity map)
Little Red Dot Abell2744-QSO1 (NIRCam Image, annotated)
This is an image from NIRCam (Near Infrared Camera) on Webb that shows Abell2744-QSO1, magnified and triply imaged by galaxy cluster Abell 2744.
Abell2744-QSO1 (QSO1) is a prototypical Little Red Dot, one of the first of hundreds of tiny glowing flecks of infrared light that Webb has found speckling the early Universe. QSO1 is roughly 1,300 light-years across and with a cosmological redshift (z) of 7, its light dates back to just 700 million years after the Big Bang, when the Universe was only 5% of its current age.
QSO1 is ideal for study because it is gravitationally lensed, both magnified and triply imaged by Abell 2744, the intervening mega-cluster of galaxies that warps its surrounding space-time.
Detailed study of the brightest of the three lensed images, QSO1A (upper right), shows that the object consists of a central supermassive black hole 50 million times the mass of the Sun, surrounded by a cloud of hydrogen and helium gas with very small amounts of heavier elements like oxygen. Unlike supermassive black holes in nearby galaxies, which make up only a tiny fraction of their host galaxy’s total mass, QSO1’s black hole contains twice as much mass as the galactic material surrounding it.
[Image description: Image with compass arrows, scale bar, and colour key. A deep field image showing objects of different size, colour, and shape. Three tiny, red circular objects are called out with small white boxes, and enlarged in pullouts labeled from top to bottom: QSO1A, QSO1B, and QSO1C. In the bottom left corner of the image are compass arrows indicating the orientation of the image on the sky. The east arrow points toward 10 o’clock. The north arrow points toward 1 o’clock. At the bottom right corner of the image is a scale bar labeled 15 arcseconds. The image width is about 5.5 times the length of the scale bar. Below the image is a colour key showing which NIRCam filters were used to create the image and which visible light colour is assigned to each filter. From left to right: F115W (blue), F150W (blue), F200W (green), F277W (green), F356W (red), F444W (red).]
Credit:NASA, ESA, CSA, L. Furtak (Ben-Gurion University), R. Maiolino (Cambridge), F. D'Eugenio (Cambridge), I. Juodžbalis (Cambridge), H. Übler (MPE), C. Marconcini (University of Florence). Image processing: A. Pagan
Fuente: ESA/Hubble/Webb Information Centre
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