Although dark matter particles continue to allude to us, astronomers continue to find evidence of them. In a recent study, they have seen its effect from the edge of visible space, when the universe was only 1.5 billion years old.
Dark matter does not emit its own light, nor does it absorb it like a dark cloud. But it does affect light gravitationally. Thus, clumps of dark matter create a gravitational lens that deflects and focuses light. Astronomers have long used this effect to map the dark matter inside galaxy clusters. You can even see this lensing effect in Webb’s recent deep-field images. Light from more distant galaxies is warped by the mass of closer galaxies, which astronomers can map to calculate the distribution of dark matter in those closer galaxies.
But in this latest study, the galaxies are so far away that there are actually no more distant galaxies. Certainly none bright enough to see his lens flare. So instead, the team used light from the cosmic microwave background (CMB). To map dark matter, the team used data from the Subaru Hyper Suprime-Cam Survey (HSC) and identified about 1.5 million faint, distant galaxies. They then used data from the Plank satellite to see how the CMB light was deflected. From this, they created a map of dark matter in the early universe.
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The cosmic microwave background seen by different satellites. Credit: NASA/JPL-Caltech/ESA
It is the most distant measurement of dark matter ever made and opens a possible gap in our current model of the universe. In the standard cosmological model, known as the LCDM model, dark energy drives the expansion of the universe, pushing galaxies apart, while the gravitational attraction of matter and dark matter causes galaxies to get together According to LCDM, the scale at which we observe fluctuations in the cosmic background drives the scale at which galaxies cluster, which tells us how densely galaxies must have clustered in the early universe . In the latter work, the amount of galaxy clusters in the first period is slightly lower than predicted by the LCDM model.
The uncertainty of the equipment’s measurements makes its result inconclusive. They may simply not have measured the scale of agglomeration. But if correct, it suggests that the laws of the universe were a little different 12 billion years ago. Combined with observations showing a strain in the rate of cosmic expansion, they could be on to something.
There are many possibilities. But the biggest success of this work is that we now have real data. It’s a great first step, and as we get more data from telescopes like the James Webb Space Telescope and the Vera Rubin Observatory, we should be able to solve this mystery and ultimately find out if the cosmic laws really were different in the dark. and in the distance past
Reference: Miyatake, Hironao, et al. “First identification of a CMB lensing signal produced by 1.5 million az ~ 4 galaxies: Constraints on matter density fluctuations at high redshift”. Physical Review Letters 129.6 (2022): 061301.
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