Today is going to be a very busy day on the cosmology front – with the Euclid Q1 Data Release coming out at 11am GMT – but I’ll start off by sharing news of final data release (DR6) by the Atacama Cosmology Telescope. This was announced yesterday and includes former colleagues at Cardiff University, so congratulations to them and all concerned. Here is a pretty picture showing one of the beautiful cosmic microwave background polarization and intensity maps:
There are three related preprints on the arXiv today:
- The Atacama Cosmology Telescope: DR6 Maps (from which the above picture was taken).
- The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and ΛCDM Parameters
- The Atacama Cosmology Telescope: DR6 Constraints on Extended Cosmological Models
There’s a lot to digest in these papers but a quick skim of the abstracts gives two pertinent points. First, from the second paper:
We find that the ACT angular power spectra estimated over 10,000 deg2, and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the ΛCDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe.
They also find that, when combined with CMB lensing from ACT and Planck, and baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI Y1), the ACT data give a “low” value for the Hubble constant: H0=68.22 ± 0.36 km s-1 Mpc-1.
The third paper also says
In general, models introduced to increase the Hubble constant or to decrease the amplitude of density fluctuations inferred from the primary CMB are not favored by our data.
The “Hubble tension” remains!
In the Dark 