Peering into the center of five of the youngest clusters of galaxies known in the universe, astronomers recently found several full-grown, cigar-chomping adults among the myriad of toddlers. The remote galaxies hail from a time when the 13.7-billion-year-old cosmos was less than 5 billion years old. Yet measurements reveal that the bodies are just as massive as galaxies like the modern-day Milky Way, which took at least 10 billions years to mature.
The findings appear to call into question the leading theory of galaxy formation, known as the dark matter model — at least as it applies to the dense regions where galaxies congregate into clusters, says Chris Collins, an astronomer at the Liverpool John Moores University in England. He and his colleagues used the infrared Subaru telescope atop Hawaii’s Mauna Kea to observe the galaxies, and the team describes the findings in the April 2 Nature.
“No doubt the theorists will want to say that tweaking [the model] in very dense regions will suffice, but I think the problem could be more general than that,” Collins says.
The highly successful model holds that the gravity of a proposed, invisible material known as cold dark matter draws together gas and stars to form galaxies. Due to the properties of dark matter, the model always builds tiny, lightweight galaxies first, merging these small-fry to make bigger bodies. Indeed, dark matter simulations suggest that at such a young age, the galaxies the team examined should have attained only 20 percent of the weight that the astronomers observed.
In the dense environment of a cluster galaxy formation is predicted to occur more quickly. Nonetheless, there doesn’t seem to have been enough time, some 4 billion to 5 billion years after the Big Bang, for the five massive galaxies to have formed by the merging of smaller galaxies, according to the model. The findings suggest that some massive galaxies formed wholesale, rather than building up stars and gas little by little as they cannibalized their neighbors.
The findings appear to call into question the leading theory of galaxy formation, known as the dark matter model — at least as it applies to the dense regions where galaxies congregate into clusters, says Chris Collins, an astronomer at the Liverpool John Moores University in England. He and his colleagues used the infrared Subaru telescope atop Hawaii’s Mauna Kea to observe the galaxies, and the team describes the findings in the April 2 Nature.
“No doubt the theorists will want to say that tweaking [the model] in very dense regions will suffice, but I think the problem could be more general than that,” Collins says.
The highly successful model holds that the gravity of a proposed, invisible material known as cold dark matter draws together gas and stars to form galaxies. Due to the properties of dark matter, the model always builds tiny, lightweight galaxies first, merging these small-fry to make bigger bodies. Indeed, dark matter simulations suggest that at such a young age, the galaxies the team examined should have attained only 20 percent of the weight that the astronomers observed.
In the dense environment of a cluster galaxy formation is predicted to occur more quickly. Nonetheless, there doesn’t seem to have been enough time, some 4 billion to 5 billion years after the Big Bang, for the five massive galaxies to have formed by the merging of smaller galaxies, according to the model. The findings suggest that some massive galaxies formed wholesale, rather than building up stars and gas little by little as they cannibalized their neighbors.
No comments:
Post a Comment