A massive galaxy with almost no dark matter

According to our primary cosmological models, about 85% of the mass in the universe is dark matter. Although repeated attempts to study this mysterious, invisible mass have not provided direct evidence, astrophysicists have been able to observe and measure its influence. Dark matter halos, the effect of general relativity on gravitational lenses and large-scale cosmic structures. With the help of next generation missions like ESA Euclid and NASA’s Nancy Grace Roman Space telescopes, dark matter won’t be a mystery for long!

Then comes something like this: A massive galaxy appears to have little or no dark matter! This is what a team of astronomers led by members of the Instituto Astrofisica de Canarias (IAC) observed when observing NGC 1277. Located 240 million light-years away in the Perseus galaxy, this lenticular galaxy is several times larger than the Milky Way. This is the first time that a massive galaxy has been discovered that shows no signs of dark matter, which poses a serious challenge to our current cosmological models.

The study was conducted under the leadership of Sebastien ComoronExtragalactic Astronomer, IAC and Chair at the University of Laguna (ULL). The Archeology of Thick Discs (ArcThick) collaboration. He was joined by researchers from the National Institute of Astrophysics, Optics and Electronics (INAOE), the National Science and Technology Council, the National Academy of Sciences of Ukraine, and the Institute of Particle and Cosmos Physics (IPARCOS). An article detailing their findings recently appeared in the journal Astronomy & Astrophysics.

Hubble Space Telescope image of a group of galaxies in the Perseus cluster of which NGC 1277 is a member. It is the bright star to the left of center in the image. Credit: ESA/Hubble

According to the standard model of cosmology – aka. The Lambda is cold dark matter (?CDM) model – dark matter played (and still does) an intrinsic role in the creation and evolution of the universe. In theory, this invisible mass existed shortly after the Big Bang and formed a halo that attracted neutral hydrogen gas into rotating disks. This gas was drawn into denser and denser clouds, triggering the formation of the first stars and galaxies. Today, the DM is a major component of all massive galaxies and is evident from their rotation curves, the lenses they form, and their interactions with surrounding stars and the intergalactic medium (IGM).

However, when the team measured the mass distribution of NGC 1277, they only observed the star’s distribution. From this, they inferred that DM could not account for more than 5% of the galactic mass at the observed radius – although their observations indicated no DM. Comoron explained recently IAC press release:

„This result is inconsistent with currently accepted cosmological models, which include dark matter. The importance of relict galaxies in helping us understand how the first galaxies formed is the reason we decided to observe NGC 1277 with an integrated field spectrum. From the spectra, we created kinematic maps that enabled us to construct the mass distribution within the galaxy for a radius of about 20,000 light years.

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In their paper, the team describes NGC 1277 as a prototypical „relic galaxy,” an extremely rare class that has not interacted with neighboring galaxies. These galaxies are believed to be remnants of giant galaxies that formed after the Big Bang. However, the ?CDM model predicts at least 10% of galaxies as massive as NGC 1277, with a maximum of 70% for this particular category. said Co-author Anna Ferré-Mateu, researcher at IAC and ULL, has two possible explanations for this discrepancy.:

„One is that the gravitational interaction with the surrounding medium within the galaxy cluster in which this galaxy resides has removed the dark matter. The other is that the dark matter was ejected from the system when the galaxy formed by the merger of protogalactic fragments, leading to relic galaxies.

This diagram shows how the diameter of the 17-billion-solar-mass black hole at the heart of the galaxy NGC 1277 compares with Neptune’s orbit around the Sun. Credit: D. Benningfield/K. Gebhardt/Stardate

However, both of these explanations are not entirely satisfactory as far as the team is concerned. In the future, the team plans to conduct observations and investigate the mystery further WHT Enhanced Area Velocity Explorer (WEAVE) on the tool William Herschel telescope (WHT), located at the Roque de los Muchachos Observatory on the island of La Palma. If WEAVE’s velocity measurements confirm that NGC 1277 does not contain DM, it could cast serious doubt on alternative theories such as modified Newtonian mechanics (MOND). said Trujillo:

„This discrepancy between observations and what we expect is a puzzle, and may be a challenge to the standard model. Although dark matter in a particular galaxy may be lost, the modified law of gravity must be universal and cannot have exceptions, so a galaxy without dark matter is a negation of this type of alternative to dark matter.

These observations point to a particularly massive supermassive black hole (SMBH) in the galaxy, which is approximately 17 billion solar masses, or 4,250 times more massive than Sagittarius A* (the SMBH at the center of the Milky Way)! According to some astronomers, black holes may be the source of DM, formed from the collapse of DM haloes during the early universe. There is also the mystery of dark matter galaxies, such as the odd case of Fast J0139+4328, which are almost entirely DM.

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Next generation tasks etc Euclid And this Nancy Grace Roman Space telescopes will provide new insights by probing the expansion of the universe since the Big Bang. These observations aim to measure the influence of dark matter (and dark energy) on the largest cosmic scales. The results of these and other studies could resolve the current debate by revealing the existence of a mysterious invisible mass, or that our understanding of gravity (as described by general relativity) should be revised.

read more: IAC, Astronomy & Astrophysics

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