This morning’s arXiv announcement contained a number of papers related to the Dark Energy Survey Y6 analysis. There is also a Zoom webinar later today at 10.30 Central Time (16.30 GMT; 13.30 in Greenland). Details can be found here.
You can find links to and abstracts of all the papers here, but I thought it would be useful to provide arXiv links to the latest batch here.
arXiv:2601.14559 Dark Energy Survey Year 6 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing – this is the key summary paper.
arXiv:2601.14484 Dark Energy Survey Year 6 Results: MagLim++ Lens Sample Selection and Measurements of Galaxy Clustering
arXiv:2601.14864 Dark Energy Survey: DESI-Independent Angular BAO Measurement
arXiv:2601.15175 Dark Energy Survey Year 6 Results: Galaxy-galaxy lensing
arXiv:2601.14833 Dark Energy Survey Year 6 Results: Magnification modeling and its impact on galaxy clustering and galaxy-galaxy lensing cosmology
arXiv:2601.14859 Dark Energy Survey Year 6 Results: Weak Lensing and Galaxy Clustering Cosmological Analysis Framework
I’ll just highlight a couple of points from the first paper listed above, which uses the now standard “3x2pt” analysis, which combines three complementary two-point correlation functions: cosmic shear; galaxy-galaxy lensing and galaxy clustering. The abstract of this paper is as follows:
A notable result is contained in the last sentence. The simplest interpretation of dark energy is that it is a cosmological constant (usually called Λ) which – as explained here – corresponds to a perfect fluid with an equation-of-state p=wρc2 with w=-1. In this case the effective mass density ρ of the dark energy remains constant as the universe expands. To parametrise departures from this constant behaviour, cosmologists have replaced this form with the form w(a)=w0+wa(1-a) where a(t) is the cosmic scale factor. A cosmological constant Λ would correspond to a point (w0=-1, wa=0) in the plane defined by these parameters, but the only requirement for dark energy to result in cosmic acceleration is that w<-1/3, not that w=-1. Results last year from DESI suggested values of w0 ≠-1 and wa≠0 , but the current DES results are consistent with w=-1; they do not constrain w0 and wa jointly.
For reference on the left you can find the (w0, wa) plane from DESI.
I thought I’d add one of the other cosmological contraint plots:
The results look qualitatively similar to previous plots but the contours have shifted a bit.
It’s Saturday once more so time for another update of activity at the Open Journal of Astrophysics. Since the last update we have published seven papers, bringing the number in Volume 9 (2026) to 11 and the total so far published by OJAp up to 459. This week has been quite busy; for only the second time in recorded history we published at least one paper each working day.
I will continue to include the announcements made on our Mastodon account (on Fediscience) to encourage you to visit it. Mastodon is a really excellent service, and a more than adequate replacement for X/Twitter which nobody should be using.
The first three papers this week were all published on Monday January 12th in the folder Astrophysics of Galaxies.
The first paper to report this week is “Rotational Kinematics in the Globular Cluster System of M31: Insights from Bayesian Inference” by Yuan (Cher) Li & Brendon J. Brewer (U. Auckland, New Zealand), Geraint F. Lewis (U. Sydney, Australia) and Dougal Mackey (independent researcher, Australia). This study uses Bayesian modelling to explore the kinematics of globular clusters in the Andromeda Galaxy, revealing distinct rotation patterns that suggest different subgroups were added at separate times.
The overlay is here:
You can find the officially accepted version on arXiv here and the announcement on Fediverse here:
New Publication at the Open Journal of Astrophysics: "Rotational Kinematics in the Globular Cluster System of M31: Insights from Bayesian Inference" by Yuan (Cher) Li & Brendon J. Brewer (U. Auckland, New Zealand), Geraint F. Lewis (U. Sydney, Australia) and Dougal Mackey
The second paper is “DESI Data Release 1: Stellar Catalogue” by Sergey Koposov (U. Edinburgh, UK) and an international cast of 67 other authors. This paper introduces and describes the stellar Value-Added Catalogue (VAC) based on DESI Data Release 1, providing measurements for over 4 million stars, including radial velocity, abundance, and stellar parameters.
The overlay for this one is here:
The official version of the paper can be found on arXiv here and the Fediverse announcement here:
New Publication at the Open Journal of Astrophysics: "DESI Data Release 1: Stellar Catalogue" by Sergey Koposov (U. Edinburgh, UK) and an international cast of 67 other authors.
New Publication at the Open Journal of Astrophysics: "On the origins of oxygen: ALMA and JWST characterise the multi-phase, metal-enriched, star-bursting medium within a ‘normal’ z>11 galaxy" by Joris Witstok (Cosmic Dawn Centre, Copenhagen, Denmark) and 37 others dotted around the world
The fourth paper this week is also in the folder Astrophysics of Galaxies. but was published on Tuesday 13th January. It is entitled “Accelerated calibration of semi-analytic galaxy formation models” by Andrew Robertson and Andrew Benson (Carnegie Observatories, USA). This paper presents a faster calibration framework for galaxy formation models, using fewer simulations for each evaluation. However, the model shows discrepancies suggesting the model needs to be made more flexible.
The overlay is here:
You can find the officially accepted version on arXiv here and the Mastodon announcement here:
New Publication at the Open Journal of Astrophysics: "Accelerated calibration of semi-analytic galaxy formation models" by Andrew Robertson and Andrew Benson (Carnegie Observatories, USA)
Next one up, published on Wednesday 14th January in the folder Cosmology and Nongalactic Astrophysics, is “Constraints from CMB lensing tomography with projected bispectra” by Lea Harscouet & David Alonso (U. Oxford), UK), Andrina Nicola (U. Manchester, UK) and Anže Slosar (Brookhaven National Laboratory, USA). This study presents angular power spectra and bispectra of DESI luminous red galaxies, finding that the galaxy bispectrum can constrain the amplitude of matter fluctuations and the non-relativistic matter fraction. The overlay is here:
You can find the officially accepted paper on arXiv here and the Mastodon announcement here:
New Publication at the Open Journal of Astrophysics: "Constraints from CMB lensing tomography with projected bispectra" by Lea Harscouet & David Alonso (U. Oxford, UK), Andrina Nicola (U. Manchester, UK) and Anže Slosar (Brookhaven National Laboratory, USA)
The sixth paper this week is “Universal numerical convergence criteria for subhalo tidal evolution” by Barry T. Chiang & Frank C. van den Bosch (Yale U., USA) and Hsi-Yu Schive (National Taiwan University, Taiwan). This was published on Thursday 15th January in the folder Cosmology and Nongalactic Astrophysics; it presents an analysis of a simulation suite that addresses the ‘overmerging’ problem in cosmological simulations of dark matter subhalos, showing that up to 50% of halos in state-of-the art simulations are unresolved. The overlay is here:
The final accepted version of this paper can be found on arXiv here. The Mastodon announcement follows:
New Publication at the Open Journal of Astrophysics: "Universal numerical convergence criteria for subhalo tidal evolution" by Barry T. Chiang & Frank C. van den Bosch (Yale U., USA) and Hsi-Yu Schive (National Taiwan University, Taiwan)
Finally for this week we have “Detectability of dark matter subhalo impacts in Milky Way stellar streams” by Junyang Lu , Tongyan Lin & Mukul Sholapurkar (UCSD, USA) and Ana Bonaca (Carnegie Observatories, USA). This was published on Friday 16th January (i.e. yesterday) in the folder Astrophysics of Galaxies. The study develops a method to estimate the minimum detectable dark matter subhalo mass in stellar streams, ranking them by sensitivity and identifying promising lines for further research.
The overlay is here:
The officially accepted version can be found on arXiv here and the Fediverse announcement here:
New Publication at the Open Journal of Astrophysics: "Detectability of dark matter subhalo impacts in Milky Way stellar streams" by Junyang Lu , Tongyan Lin & Mukul Sholapurkar (UCSD, USA) and Ana Bonaca (Carnegie Observatories, USA)
Welcome to the first proper update for 2026 from the Open Journal of Astrophysics. The New Year brings us to Volume 9. In many countries, especially in Europe, Christmas is celebrated on January 6th so this week was also affected by the holiday season. Nevertheless, since the last update we have published four papers, bringing the number in Volume 9 (2026) to 4 and the total so far published by OJAp up to 452.
The first paper this week (and of course the first of 2026) is “A targeted, parallax-based search for Planet Nine” by Hector Socas-Navarro and Ignacio Trujillo (both of the Instituto de Astrofísica de Canaria, Spain). This article describes a targeted search for the hypothesized Planet Nine in the outer solar system, using parallax position shifts. No credible candidates were found within the observed field. It was published on Tuesday January 6th in the folder Earth and Planetary Astrophysics. The overlay is here:
You can find the officially accepted version on arXiv here and the announcement on Fediverse here:
New Publication at the Open Journal of Astrophysics: "A targeted, parallax-based search for Planet Nine" by Hector Socas-Navarro and Ignacio Trujillo (Instituto de Astrofísica de Canaria, Spain)
The second paper is “Going beyond S8: fast inference of the matter power spectrum from weak-lensing surveys” by Cyrille Doux (Université Grenoble Alpes, France) and Tanvi Karwal (U. Chicago, USA). This was published on Wednesday January 7th in the folder Cosmology and Nongalactic Astrophysics and it presents a new framework to extract the scale-dependent matter power spectrum from cosmic shear and CMB lensing measurements, revealing a consistent suppression in the matter power spectrum in galaxy-lensing. The overlay is here:
The official version of the paper can be found on arXiv here and the Fediverse announcement here:
New Publication at the Open Journal of Astrophysics: "Going beyond $S_{8}$: fast inference of the matter power spectrum from weak-lensing surveys" by Cyrille Doux (Université Grenoble Alpes, France) and Tanvi Karwal (U. Chicago, USA)
Next we have “Constraining the Stellar-to-Halo Mass Relation with Galaxy Clustering and Weak Lensing from DES Year 3 Data” which is led by G. Zacharegkas et al. (Argonne National Laboratory, USA) and has 102 other authors too numerous to list by name from many institutions around the world again too numerous to list by name. It presents a framework to analyze the relationship between a galaxy’s stellar mass and its dark matter halo mass, using data from the Dark Energy Survey. The findings align with previous results. This paper was published on Thursday January 8th in the folder Astrophysics of Galaxies. The overlay is here:
The official version can be found on arXiv here and the Fediverse announcement is here:
New Publication at the Open Journal of Astrophysics: "Constraining the Stellar-to-Halo Mass Relation with Galaxy Clustering and Weak Lensing from DES Year 3 Data" by G. Zacharegkas et al. (Argonne National Laboratory, USA) and 102 others based in numerous countries.
New Publication at the Open Journal of Astrophysics: "Distance measurements from the internal dynamics of globular clusters: Application to the Sombrero galaxy (M 104)" by Katja Fahrion (University of Vienna, Austria) and 9 others based in Spain, Australia, UK, USA, Brazil, Germany and Switzerland.
The Ideas of March are come, so it’s time for another update of papers published at the Open Journal of Astrophysics. Since the last update we have published two papers, which brings the number in Volume 8 (2025) up to 27 and the total so far published by OJAp up to 262.
Here is the overlay, which you can click on to make larger if you wish:
You can read the officially accepted version of this paper on arXiv here.
The other paper published this week is “Exploring Symbolic Regression and Genetic Algorithms for Astronomical Object Classification” by Fabio Ricardo Llorella (Universidad Internacional de la Rioja, Spain) & José Antonio Cebrian (Universidad Laboral de Córdoba, Spain), which came out on Thursday 13th March. This one is in the folder marked Astrophysics of Galaxies and it discusses the classification of astronomical objects in the Sloan Digital Sky Survey SDSS-17 dataset using a combination of Symbolic Regressiion and Genetic Algorithms.
It’s Saturday morning again and time to post an update of activity at the Open Journal of Astrophysics. As last week there are six papers to announce, bringing the count in Volume 7 (2024) up to 93 and the total altogether up to 208.
In chronological order, the six papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.
The accepted version of this paper can be found on the arXiv here.
The third paper is “Image formation near hyperbolic umbilic in strong gravitational lensing” by Ashish Kumar Meena (Ben Gurion University, Israel) and Jasjeet Singh Bagla (IISER Mohali, India). It presents a detailed theoretical discussion of a particular form of strong gravitational lensing and its observational consequences; it is in the folder Astrophysics of Galaxies and was published on October 15th 2024.
The overlay is here:
The officially accepted version can be found on arXiv here.
You can find the official accepted version on the arXiv here.
Finally for this week we have “On the nature of the C IV-bearing circumgalactic medium at 𝒛∼𝟏” by Suyash Kumar, Hsiao-Wen Chen, Zhijie Qu & Mandy C. Chen (U. Chicago), Fakhri S. Zahedy (U. North Texas), Sean D. Johnson (Carnegie Observatories), Sowgat Muzahid (IUCAA, India) and Sebastiano Cantalupo (U. Milan Bicocca)
The overlay is here
You can find the officially-accepted version on arXiv here.
A few months ago I posted an item about the release new results from the Dark Energy Spectroscopic Instrument (DESI). That was then followed by a presentation explaining the details which you can find here to find out more about the techniques involved. At the time the new DESI results garnered a lot of media attention much of it about claims that the measurements provided evidence for “New Physics”, such as evolving dark energy. Note that the DESI results themselves did not imply this. Only when combined with supernova measurements did this suggestion arise.
Now there’s a new preprint out by George Efstathiou of Cambridge. The abstract is here:
Recent results from the Dark Energy Spectroscopic Instrument (DESI) collaboration have been interpreted as evidence for evolving dark energy. However, this interpretation is strongly dependent on which Type Ia supernova (SN) sample is combined with DESI measurements of baryon acoustic oscillations (BAO) and observations of the cosmic microwave background (CMB) radiation. The strength of the evidence for evolving dark energy ranges from ~3.9 sigma for the Dark Energy 5 year (DES5Y) SN sample to ~ 2.5 sigma for the Pantheon+ sample. Here I compare SN common to both the DES5Y and Pantheon+ compilations finding evidence for an offset of ~0.04 mag. between low and high redshifts. Correcting for this offset brings the DES5Y sample into very good agreement with the Planck LCDM cosmology. Given that most of the parameter range favoured by the uncorrected DES5Y sample is discrepant with many other cosmological datasets, I conclude that the evidence for evolving dark energy is most likely a result of systematics in the DES5Y sample.
Here are a couple of figures from the paper illustrating the difference in parameter constraints using the uncorrected (left) and corrected (right) Dark Energy (Survey) 5 year Supernova sample.
The y-axis shows a parameter wa, which is zero in the standard model with non-evolving dark energy; the non-zero value implied by the left hand panel using the uncorrected data.
Just as with the Hubble Tension I blogged about yesterday, the evidence for a fundamental revision of our standard model may be nothing of the sort but some kind of systematic error. I think we can expect a response from the Dark Energy Survey (DES) team. Grab your popcorn.
Some important cosmological results have just been announced by the Dark Energy Survey Collaboration. I haven’t had time to go through them in detail but I thought it was worth doing a quick post here to draw attention to them. The results concern a sample of Type Ia supernovae (SN Ia) discovered during the full five years of the Dark Energy Survey (DES) Supernova Program, which contains about 1500 new Type Ia Supernovae that can be used for cosmological analysis. The paper is available on the arXiv here; the abstract is:
The key numerical result of interest is the equation-of-state parameter for dark energy, designated by w, which occurs in the (assumed) relationship between pressure p and effective mass density ρ of the form p=wρc2. A cosmological constant – which for many cosmologists is the default assumption for the form of dark energy – has w=-1 as I explained here. This parameter is one of the things Euclid is going to try to measure, using different methods. Interestingly, the DES results are offset a bit from the value of -1, but with quite a large uncertainty.
While the results for the equation-of-state parameter are somewhat equivocal, one thing that is clear is that the new SNIa measurements do confirm the existence of dark energy, in that the data can only be described by models with accelerating expansion, as dramatically demonstrated in this Figure:
I think this figure – or versions of it – will very rapidly appear in public talks on cosmology, including my own!
These constraints, derived using DES Y1 measurements of galaxy clustering, galaxy-galaxy lensing, and weak lensing cosmic shear are compared with those obtained from the cosmic microwave background using Planck data, and also combined with them to produce a joint constraint. Following usual practice, the contours are 68% and 95% posterior probability regions.
The central values of DES and Planck values are different, but the discrepancy is only marginal. Compare this with a an equivalent diagram from a paper I discussed last year.
The KIDS analysis used to produce this plot uses only weak lensing tomography, so you can see that using additional measures reduces the viable region in this parameter space.
It’s great to see new data coming in, but at first sight it seems it is tending to confirm the predictions of the standard cosmological model, rather than providing evidence of departures from it.
Incidentally, this little video shows the extent to which the Dark Energy Survey is a global project, including some of my former colleagues at the University of Sussex!
I’m a bit late onto this story which has already been quite active in the media today, and has generated an associated flurry of activity on social media, but I thought it was still worth passing it on via the medium of this blog. The Dark Energy Survey has just released a number of papers onto the arXiv, the most interesting of which (to me) is entitled Wide-Field Lensing Mass Maps from DES Science Verification Data. The abstract reads as follows (the link was added by me):
Weak gravitational lensing allows one to reconstruct the spatial distribution of the projected mass density across the sky. These “mass maps” provide a powerful tool for studying cosmology as they probe both luminous and dark matter. In this paper, we present a weak lensing mass map reconstructed from shear measurements in a 139 deg^2 area from the Dark Energy Survey (DES) Science Verification (SV) data overlapping with the South Pole Telescope survey. We compare the distribution of mass with that of the foreground distribution of galaxies and clusters. The overdensities in the reconstructed map correlate well with the distribution of optically detected clusters. Cross-correlating the mass map with the foreground galaxies from the same DES SV data gives results consistent with mock catalogs that include the primary sources of statistical uncertainties in the galaxy, lensing, and photo-z catalogs. The statistical significance of the cross-correlation is at the 6.8 sigma level with 20 arcminute smoothing. A major goal of this study is to investigate systematic effects arising from a variety of sources, including PSF and photo-z uncertainties. We make maps derived from twenty variables that may characterize systematics and find the principal components. We find that the contribution of systematics to the lensing mass maps is generally within measurement uncertainties. We test and validate our results with mock catalogs from N-body simulations. In this work, we analyze less than 3% of the final area that will be mapped by the DES; the tools and analysis techniques developed in this paper can be applied to forthcoming larger datasets from the survey.
This is by no means a final result from the Dark Energy Survey, as it was basically put together in order to test the telescope, but it is interesting from the point of view that it represents a kind of proof of concept. Here is one of the key figures from the paper which shows a reconstruction of the mass distribution of the Universe (dominated by dark matter) obtained indirectly by the Dark Energy Survey using distortions of galaxy images produced by gravitational lensing by foreground objects, onto which the positions of large galaxy clusters seen in direct observations have been plotted. Although this is just a small part of the planned DES study (it covers only 0.4% of the sky) it does seem to indicate that the strong concentrations of dark matter (red) do corrrelate with the positions of concentrations of galaxy clusters.
It all seems to work, so hopefully we can look forward to lots of interesting science results in future!
P.S. When I first saw the map it looked like a map of the North of England Midlands and I was surprised to see that the survey showed such strong support for the Greens…
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In the Dark 