A monster galaxy is spotted from the ancient Universe — it lived fast and died young — what killed XMM-2599?
A monster galaxy from the early Universe, XMM-2599, lived out its life just a billion years after the Big Bang, before dying a mysterious death when the Universe was just 13 percent of its current age.
Galaxies like the Milky Way produce roughly one new star each year, but XMM-2599 developed a flurry of stars when it first formed, reaching a mass of more than 300 billion Suns. Star production then quickly shut down, making XMM-2599 a “dead galaxy.” Why this fast-living galaxy shut down stellar formation so quickly is a new mystery for astronomers to solve.
“XMM-2599 formed most of its stars in a huge frenzy when the universe was less than 1 billion years old, and then became inactive by the time the universe was only 1.8 billion years old,” said Benjamin Forrest, of the University of California, Riverside (UCR) Department of Physics and Astronomy.
Live Large, Die Young
Such massive galaxies are predicted to have formed early in the evolution of the Universe, but finding them has been exceedingly challenging. In addition, theories predict that galaxies with masses as large as XMM-2599 should be actively producing stars, making the discovery of this galaxy even more unexpected.
“While galaxies with similarly extreme stellar masses are reproduced in some simulations at early times, such a lack of ongoing star formation is not seen there… challenging our current understanding of how ultra-massive galaxies form and evolve in the early universe,” researchers wrote in the Astrophysical Journal.
At the peak of its production, the team estimates that XMM-2599 formed roughly 1,000 solar masses worth of stars each year. The body may be an example of a newly-discovered class of dusty galaxies recently discovered by astronomers using radio telescopes.
Even in the present-day Universe, this ancient family of stars would still be considered sizable.
“XMM-2599 has a mass equal to about three times the mass of the present-day Milky Way. However, remember that we are observing XMM-2599 as it appeared about 12 billion years ago when the Universe was only 1.8 [billion years] old. XMM-2599’s mass at that epoch is huge considering that the Milky Way would have had very little mass at the same epoch,” Gillian Wilson, professor of physics and astronomy at UCR, tells The Cosmic Companion.
Every galaxy in the Universe is believed to be home to a supermassive black hole near its core. This enigmatic region at the center of XMM-2599 could be responsible for the short, energetic life of this body, researchers speculate.
“From X-ray observations, we know that XMM-2599 does already have a supermassive black hole. Indeed by turning on and generating huge amounts of energy the black hole could be what is responsible for turning star formation off by heating cool gas in the galaxy which would otherwise be available to continue to form new stars,” Wilson explains.
If the supermassive black hole in XMM-2599 is shown not to be responsible for the early death of this ancient galaxy, this finding could force astronomers and astrophysicists to rewrite much of what we know about mechanisms driving star formation in galaxies of the early Universe.
MOSFIRE When Ready!
The team utilized the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) instrument at the W.M. Keck Observatory in Hawaii to carry out their study.
When examining targets, MOSFIRE is able to study a field more than six degrees across — large enough to hold 150 full moons in its sights. A total of 46 slits are capable of imaging dozes of objects in its field of view at a single time. This robotic slit mask system can then realign itself for another observation in just a few minutes.
In addition to MOSFIRE, the pair of telescopes at the Keck Observatory utilize active optics to constantly correct tiny shifts in the position and alignment of their primary mirrors to correct for movements of the optics caused by gravity and moving the instruments.
Atmospheric disturbances are also largely eliminated by adaptive optics, which creates an artificial guide star several miles above the ground. Analysis of distortions of this light is used to constantly alter the shape of a small mirror, correcting for distortions in the atmosphere.
The Future Looks Bright. Maybe.
Due to the enormous distance to this ancient body, the light we see today from XMM-2599 shows us that galaxy as it appeared eons ago. How this ancient galaxy changed in the last 11.7 billion years remains a mystery. This family of stars may have joined together with other galaxies into a bright, massive cluster, or remained alone for billions of years — there is no way to tell for certain.
“We have caught XMM-2599 in its inactive phase. We do not know what it will turn into by the present day. We know it cannot lose mass. An interesting question is what happens around it. As time goes by, could it gravitationally attract nearby star-forming galaxies and become a bright city of galaxies?” Wilson explains.
In the far distant future, our own Milky Way galaxy will also stop producing stars, and our local family of stars will die.
“The Milky Way will eventually run out of fuel (cold gas) and stop forming new stars. However, this will not happen for a long time yet. What’s remarkable about XMM-2599 is that it formed so many stars so quickly and then died so rapidly,” Wilson describes.
James Maynard is the founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat.
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