In the Dark

I wish to draw your attention to a clutch of new papers out on the arXiv today (here, here and here) which describe latest results from the Atacama Cosmology Telescope (ACT for short). There was a webinar about this yesterday, which I failed to attend because I forgot about it.

The first of the papers listed above summarizes the key science results, which include a mass map obtained from gravitational lensing of the cosmic microwave background and its implications for cosmology.

As cosmic background photons propagate freely through space, i.e. without scattering, from the time of recombination to the observer, they are deflected by the gravitational effect of the large-scale distribution of matter in the Universe. This lensing effect leaves imprints in the temperature and polarization anisotropies, which can be used to reconstruct a map of the lensing potential, the gradient of which determines the lensing deflections. Structures in the CMB temperature pattern look bigger on the sky if we view them through an overdense clump of dark matter. By looking how the typical size of hot and cold spots in the CMB temperature map vary across the sky, it is possible to reconstruct the lensing deflections and hence the distribution of dark matter integrated along the line of sight. Since the structure through which the radiation passes is changing with time, this sort of map can provide constraints on models for the evolution of structure.

To cut a long story short, here is the map obtained using Data Release 6 of the ACT data over about 25% of the sky:

There’s a lot of information in the three papers but the key conclusion can be found in the last sentence of the abstract of the first paper:

Our results provide independent confirmation that the universe is spatially flat, conforms with general relativity, and is described remarkably well by the ΛCDM model, while paving a promising path for neutrino physics with gravitational lensing from upcoming ground-based CMB surveys.

Nothing revolutionary, then, but interesting nevertheless. There is an article on the BBC website about these results.

This entry was posted on April 12, 2023 at 10:21 am and is filed under The Universe and Stuff with tags ACT, arXiv:2304.05196, arXiv:2304.05203, arXiv:2305.05202, Atacama Cosmology Telescope, Cosmic Microwave Background, Cosmology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.