Last week, when I wrote about the new results from the Dark Energy Spectroscopic Instrument (DESI) I mentioned that there would be a seminar here at ICCUB about that very topic. Well, the seminar, by Licia Verde & Héctor Gil Marin, was recorded and here it is:
Archive for DESI
Cosmology Talks: Cosmological Constraints from BAO
Posted in The Universe and Stuff, YouTube with tags astronomy, Cosmology, Cosmology Talks, Dark Energy, Dark Energy Spectroscopic Instrument, DESI, Physics, Science, Shaun Hotchkiss, Universe on April 5, 2024 by telescoperHere’s another video in the Cosmology Talks series curated by Shaun Hotchkiss. This one very timely after yesterday’s announcement. Here is the description on the YouTube page:
The Dark Energy Spectroscopic Instrument (DESI) has produced cosmological constraints! And it is living up to its name. Two researchers from DESI, Seshadri Nadathur and Andreu Font-Ribera, tell us about DESI’s measurements of the Baryon Acoustic Oscillations (BAO) released today. These results use one full year of DESI data and are the first cosmological constraints from the telescope that have been released. Mostly, it is what you might expect: tighter constraints. However, in the realm of the equation of state of dark energy, they find, even with BAO alone, that there is a hint of evidence for evolving dark energy. When they combine their data with CMB and Supernovae, who both also find small hints of evolving dark energy on their own, the evidence for dark energy not being a cosmological constant jumps as high as 3.9σ with one combination of the datasets. It seems there still is “concordance cosmology”, it’s just not ΛCDM for these datasets. The fact that all three probes are tentatively favouring this is intriguing, as it makes it unlikely to be due to systematic errors in one measurement pipeline.
My own take is that the results are very interesting but I think we need to know a lot more about possible systematics before jumping to conclusions about time-varying dark energy. Am I getting conservative in my old age? These results from DESI do of course further underline the motivation for Euclid (another Stage IV survey), which may have an even better capability to identify departures from the standard model.
P.S. Here’s a nice graphic showing the cosmic web showing revealed by the DESI survey:
First Light at the Dark Energy Spectroscopic Instrument
Posted in The Universe and Stuff with tags Cosmology, Dark Energy, Dark Energy Cosmology, Dark Energy Spectroscopic Instrument, DESI, Galaxy redshift surveys, redshift surveys on November 4, 2019 by telescoperWhile I was away last week there was quite a lot of press coverage (e.g. here) about the new Dark Energy Spectroscopic Instrument, which has just seen first light. I didn’t have time to mention this until now, and in any case I have little to add to the coverage that has already appeared, but it does give me the excuse to post this nice video – which features quite a few people I actually know! – to describe the huge galaxy survey that DESI will perform. It’s hard to believe that when I started in the field in 1985 the largest such survey, which took several years to compile, had only a few thousand galaxies in it. The DESI instrument will be able to determine spectra of more sources than that in a single pointing of the telescope that lasts about 20 minutes. Overall it should determine redshifts of over 35 million galaxies! Vorsprung durch Technik.