This is an unprecedented finding for a galaxy of its size, multiple times heavier than our Milky Way, causing the cosmological community to revisit their understanding of the universe's elusive matter.
In a groundbreaking revelation, Sebastièn Comerón and his research team at the IAC and the University of La Laguna (ULL) have challenged the existing cosmological models by discovering that the massive galaxy NGC 1277 does not contain any dark matter.
A Massive Galaxy With No Dark Matter?
This is an unprecedented finding for a galaxy of its size, multiple times heavier than our Milky Way, causing the cosmological community to revisit their understanding of the universe’s elusive matter.
Generally, substantial amounts of dark matter, a unique variant that interacts differently from ordinary matter, inhabit massive galaxies according to the current standard cosmological model. Its existence can only be verified through the substantial gravitational force it imparts on nearby stars and gases, which can be observed.
A Rare “Relic Galaxy”
NGC 1277, often classified as a “relic galaxy”, has remained untouched by its neighbors. These galaxies are scarce, and are considered leftovers from giant galaxies that formed during the universe’s infancy.
Relic galaxies play a pivotal role in comprehending the formation of the first galaxies, making NGC 1277 an excellent subject for study using an integral field spectrograph, states Comerón. They constructed kinematic maps from spectra which enabled them to determine the mass distribution within the galaxy up to a distance of approximately 20,000 light years.
A Surprising Distribution of Mass
They were startled to find that the mass distribution within NGC 1277 was solely that of stars, leading them to conclude that there could be no more than 5% of dark matter within the observed radius. This finding was compatible with a total lack of dark matter.
However, current cosmological models anticipated that a galaxy the size of NGC 1277 should contain dark matter contributing to at least 10% of its mass, and possibly up to 70%. This disparity between expectations and reality presents a challenge for the standard cosmological model, suggests Ignacio Trujillo, a fellow researcher at the IAC and the ULL.
Possible Explanations for Dark Matter’s Absence
The researchers propose two potential explanations for NGC 1277’s dark matter absence. One theory suggests gravitational interaction with surrounding elements within the galaxy cluster might have expelled the dark matter, says Anna Ferré-Mateu, another researcher at the IAC and the ULL. Alternatively, the formation of the relic galaxy might have ejected the dark matter during the merging of protogalactic fragments.
Neither of these theories provides a completely satisfactory explanation, leaving researchers grappling with the mystery of a massive galaxy’s formation without dark matter, states Comerón. The team is planning further observations with the WEAVE instrument on the William Herschel Telescope at the Roque de los Muchachos Observatory, located in the Canary Islands, to investigate further.
A Possible Challenge for Alternative Models
If it is confirmed that NGC 1277 is devoid of dark matter, this will seriously question alternative theories for dark matter, especially those suggesting that a slight change in the law of gravity on larger scales explains most of the gravitational attraction within galaxies. As Trujillo notes, while a specific galaxy may lose its dark matter, a modified law of gravity must be universal and not allow exceptions, making a galaxy without dark matter a challenge to these alternative theories.
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