Some weeks ago I posted an item about recent results that have emerged from the DESI (Dark Energy Spectroscopic Instrument) Collaboration. I have been a bit busy since then but I just saw that there is one of those Cosmology Talks about these results which I thought I would pass on. The contributors are Arnaud de Mattia, Hector Gil-Marín and Pauline Zarrouk and they are talking about the analsysis they have done using the “full shape” of the galaxy power spectrum. It’s quite a long video, but very illuminating.
Archive for Cosmology
Cosmology Talks: Recent DESI Power Spectrum Results
Posted in The Universe and Stuff with tags Cosmology, Cosmology Talks, Dark Energy, Dark Energy Spectroscopic Instrument, DESI, Physics on December 12, 2024 by telescoperNew Results from DESI
Posted in Barcelona, The Universe and Stuff with tags astronomy, Cosmology, Dark Energy, Dark Energy Spectroscopic Instrument, dark matter, DESI, ICCUB, Physics on November 20, 2024 by telescoper
I’ve just got time between meetings to mention that a clutch of brand new papers has emerged from the DESI (Dark Energy Spectroscopic Instrument) Collaboration. There is a press release discussing the results from the Lawrence Berkeley Laboratory here and one from the ICCUB in Barcelona here; several members of the group I visited there during sabbatical are working on DESI. Congratulations to them.
I haven’t had time to read them yet, but a quick skim suggests that the results are consistent with the standard cosmological model.
The latest batch contains three Key Publications:
- DESI Collaboration et al., DESI 2024 II: Sample Definitions, Characteristics, and Two-point Clustering Statistics
- DESI Collaboration et al., DESI 2024 V: Full-Shape Galaxy Clustering from Galaxies and Quasars
- DESI Collaboration et al., DESI 2024 VII: Cosmological Constraints from the Full-Shape Modeling of Clustering Measurements
together with the companion supporting papers:
- Ishak et al. (2024), Modified Gravity Constraints from the Full Shape Modeling of Clustering Measurements from DESI 2024
- Rosado-Marín et al. (2024), Mitigating Imaging Systematics for DESI 2024 Emission Line Galaxies and Beyond
- Bianchi et al. (2024), Characterization of DESI fiber assignment incompleteness effect on 2-point clustering and mitigation methods for Y1 analysis
- Forero-Sánchez et al. (2024), Analytical and EZmock covariance validation for the DESI 2024 results
- Findlay et al. (2024), Exploring HOD-dependent systematics for the DESI 2024 Full-Shape galaxy clustering analysis
The links lead to the arXiv version of these papers. These articles can also be found, along with previously released publications by the DESI Collaboration, here.
Anyone who has read the latest papers is welcome to comment through the box below!
Three New Publications at the Open Journal of Astrophysics
Posted in OJAp Papers, Open Access, The Universe and Stuff with tags arXiv:2403.07313v2, arXiv:2405.00147v2, arXiv:2407.14584v2, cosmic shear, Cosmology, Cosmology and NonGalactic Astrophysics, Diamond Open Access, High-Energy Astrophysical Phenomena, shear ratios, supernovae, The Open Journal of Astrophysics, weak gravitational lensing on November 2, 2024 by telescoperIt’s Saturday, so it’s time once again for another summary of business at the Open Journal of Astrophysics. This week I have three papers to announce, which brings the total we have published so far this year (Vol. 7) to 98 and the total published by OJAp to 213.
First one up, published on Tuesday 29th October 2024, is “Cosmology with shear ratios: a joint study of weak lensing and spectroscopic redshift datasets” by Ni Emas & Chris Blake (Swinburne U., Australia), Rossana Ruggeri (Queensland U, Australia) and Anna Porredon (Ruhr University, Bochum, Germany). This paper is in the folder marked Cosmology and NonGalactic Astrophysics. The paper investigates the use of shear ratios as a cosmological diagnostic, with applications to lensing surveys
Here is a screen grab of the overlay, which includes the abstract:
You can read the paper directly on arXiv here.
The second paper to present, also published on Tuesday 29th October 2024, is “Echo Location: Distances to Galactic Supernovae From ASAS-SN Light Echoes and 3D Dust Maps” by Kyle D. Neumann (Penn State), Michael A. Tucker & Christopher S. Kochanek (Ohio State), Benjamin J. Shappee (U. Hawaii), and K. Z. Stanek (Ohio State), all based in the USA. This paper is in the folder marked High-Energy Astrophysical Phenomena and it presents a new approach to estimating the distance to a source by combining light echoes with recent three-dimensional dust maps with application to supernova distances.
The overlay looks like this:
You can read this paper directly on the arXiv here.
Last, but by no means least, comes “A deconstruction of methods to derive one-point lensing statistics” by Viviane Alfradique (Universidade Federal do Rio De Janeiro, Brazil), Tiago Castro (INAF Trieste, Italy), Valerio Marra (Trieste), Miguel Quartin (Rio de Janeiro), Carlo Giocoli (INAF Bologna, Italy), and Pierluigi Monaco (Trieste). Published in the folder marked Cosmology and NonGalactic Astrophysics, it describes a comparative study of different methods of approximating the one-point probability density function (PDF) for use in the statistical analysis of gravitational lensing.
Here is a screengrab of the overlay:
To read the accepted version of this on the arXiv please go here.
That’s it for this week. I hope to post another update next weekend, by when we might well have reached a century for this year!
Space Week 2024: The Universe according to Euclid
Posted in Biographical, Books, Talks and Reviews, Euclid, The Universe and Stuff with tags Cosmology, Dark Energy, dark matter, Euclid, European Space Agency, Space Week on October 10, 2024 by telescoper
I had a very busy day yesterday culminating in the Space Week event I blogged about a few weeks ago. There was a good attendance – lots of young kids as well as adults – and the lecture room was very full. We could probably have filled a much bigger room, actually, but had been moved to a smaller venue and had to close registrations very early to avoid having too many people. I’d guess we had about 350. My talk was the last one, and didn’t finish until 8.30 by which time I was definitely ready for a pint.
You can find the slides I used for my presentation, The Universe according to Euclid, here.
There was an official photographer there who took quite a few pictures but I haven’t seen any of them yet. I’ll post a selection if and when I get them.
Dark Matter from Primordial Black Holes?
Posted in The Universe and Stuff with tags arXiv:2402.14069, arXiv:2402.17823, Cosmology, Cosmology Talks, dark matter, PBH, Physics, primordial black holes, Science, Universe on September 27, 2024 by telescoperWe live in a cyclic universe of a sort because every few years somebody tries to resurrect the idea that dark matter is somehow related to primordial black holes, i.e. black holes formed in the very early stages of the history of the Universe so that they have masses much smaller than black holes formed more recently by the collapse of stars or the merger of other black holes. If it forms very early the mass of a PBH could in principle be very small, much less than a star or a planet. The problem with very small black holes is that they evaporate very quickly via Hawking Radiation so would not survive the 14 billion years or so needed to still be in existence today and able to be dark matter.
An idea that was used in the past to circumvent this issue was that something might stop Hawking Radiation proceeding to reduce the mass of a PBH to zero, leaving a relic of finite mass usually taken to be the Planck mass. The suggestion has returned in different (but still speculative) guise recently, fueling a number of media articles of varying degrees of comprehensibility, e.g. here. The technical papers on which these articles are based can be found here and here.
Fortunately, there is now one of those excellent Cosmology Talks explaining the latest idea of how Hawking Radiation might break down and what the consequences are for Primordial Black Holes as a form of Dark Matter.
Evolving Dark Energy or Supernovae Systematics?
Posted in The Universe and Stuff with tags Cosmology, Dark Energy, Dark Energy Spectroscopic Instrument, Dark Energy Survey, DES, DESI, evolving dark energy, Pantheon on August 15, 2024 by telescoperA 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.
Three New Publications at the Open Journal of Astrophysics
Posted in OJAp Papers, Open Access, The Universe and Stuff with tags arXiv:2311.17862v2, arXiv:2402.00928v3, arXiv:2404.17078v2, Astrophysics of Galaxies, binary systems, Brightest Cluster Galaxies, Cold Dark Matter, compact objects, Cosmology, Gravitational Lensing, High-Energy Astrophysical Phenomena, LAMOST J1010+2358, pair-instability supernova, Solar and Stellar Astrophysics, Zwicky Transient Facility on August 10, 2024 by telescoperIt’s Saturday so it’s time once again for another roundup of business at the Open Journal of Astrophysics. After last week’s summer lull, this week I have three papers to announce, which brings the total we have published so far this year (Vol. 7) to 67 and the total published by OJAp to 182.
First one up, published on 7th August 2024, is “Brightest Cluster Galaxy Offsets in Cold Dark Matter” by Jonathan Katz of Washington University (St Louis, Missouri, USA), a simulation-based study of the distribution of the position of brightest cluster galaxies relative to the dark matter distribution and its possible use as a cosmological probe. The authors are Cian Roche (MIT), Michael McDonald (MIT), Josh Borrow (MIT), Mark Vogelsberger (MIT), Xuejian Shen (MIT), Volker Springel (MPA Garching), Lars Hernquist (Harvard), Ruediger Pakmor (Harvard), Sownak Bose (Durham, UK) and Rahul Kannan (York U., Canada). This paper is in the folder marked Astrophysics of Galaxies.
Here is a screen grab of the overlay, which includes the abstract:
You can read the paper directly on arXiv here.
The second paper to present is “LAMOST J1010+2358 is not a Pair-Instability Supernova Relic” by five authors based in the USA: Pierre Thibodeaux (Chicago), Alexander P. Ji (Chicago), William Cerny (Yale), Evan N. Kirby (Notre Dame) and Joshua D. Simon (Carnegie Observatories) . As the title makes clear, the paper presents arguments against previous claims that a particular star is not a pair-instability supernova relic. This paper is in the folder marked Solar and Stellar Astrophysics. It was published on Friday August 9th 2024.
The overlay looks like this:
You can read this paper directly on the arXiv here.
Last, but by no means least, comes “A Pilot Search for Gravitational Self-Lensing Binaries with the Zwicky Transient Facility“, results of a trial search for signals of gravitational lensing of one component in a binary system by a compact companion, with a discussion of future prospects for larger surveys. This one, which was also published on 9th August, is in the folder marked High-Energy Astrophysical Phenomena. The authors are Allison Crossland & Eric C Bellm (U. Washington), Courtney Klein (UC Irvine), James R. A. Davenport (U. Washington), Thomas Kupfer (Hamburg Observatory) and Steven L. Groom, Russ R. Laher & Reed Riddle (Caltech).
Here is a screengrab of the overlay:
To read the accepted version of this on the arXiv please go here.
That’s it for this week. I hope to post another update next weekend.
R.I.P. Peter Thomas (1961-2024)
Posted in R.I.P. with tags astronomy, Cosmology, Peter Thomas, Physics, Sussex University, University of Cambridge on July 25, 2024 by telescoperOnce again I have to use this blog to pass on some very sad news. Professor Peter Thomas of Sussex University passed away last weekend at the age of 62.
Peter Thomas (left) joined the University of Sussex as a lecturer in the Astronomy Centre in 1989 and remained there for his entire career. I know from my own time as Head of School that he was an excellent colleague. who made huge contributions to the University and indeed to his research discipline of cosmology.
Peter studied Mathematics at Cambridge University, graduating in 1983 and then did Part III (also known as the Certificate of Advanced Study) which he obtained in 1984. He stayed in Cambridge to do a PhD in the Institute of Astronomy under the supervision of Andy Fabian on Cooling Flows and Galaxy Formation, which he completed in 1987. He then spent a couple of years in Toronto as a Postdoctoral Fellow at the Canadian Institute for Theoretical Astrophysics (CITA) before taking up his lectureship at Sussex in 1989. His main research interests were in in the areas of galaxy formation, including numerical and semi-analytic models, and computer simulations of the formation of clusters of galaxies. He was a widely known and very highly respected researcher in the field of theoretical cosmology and extragalactic astrophysics.
I was a PDRA in the Astronomy Centre at Sussex when Peter joined in 1989; he was Professor in the Department of Physics & Astronomy when I returned there as Head of School of Mathematical and Physical Sciences in 2013, a position he himself subsequently held. He was a much-valued member of staff who made huge contributions to the Astronomy Centre, the Department of Physics & Astronomy, the School of Mathematical and Physical Sciences, and the University of Sussex as a whole. I also remember him as a colleague on various panels for PPARC and then STFC on which he served diligently.
Having known Peter for 35 years, and being of similar age, it was a shock to hear that he passed away. I understand that he had been suffering from cancer for over a year. I send my deepest condolences to his family, friends and colleagues. I understand that his funeral will be a private family affair, but there will be a more public occasion to celebrate his life at a later date.
Two New Publications at the Open Journal of Astrophysics
Posted in OJAp Papers, Open Access, The Universe and Stuff with tags arXiv:2401.16351v3, arXiv:2405.08066v2, Astrophysics of Galaxies, Cosmology, Cosmology and NonGalactic Astrophysics, galaxy clusters, galaxy formation, Sunyaev-Zel'dovich Effect, The Open Journal of Astrophysics on July 13, 2024 by telescoperAnother Saturday, another update of the Open Journal of Astrophysics. Since the last update we have published two more papers, taking the count in Volume 7 (2024) up to 56 and the total published by OJAp up to 171. Both these papers were published on Thursday 11th July 2024.
The first paper of the most recent pair, published on July 3rd 2024, is “Sunyaev-Zeldovich signatures from non-thermal, relativistic electrons using CMB maps” by Sandeep Kumar Acharya of The Open University of Israel, Ra’anana, Israel. This article presents a discussion the possible effects of non-thermal electron energy distributions on the form of Sunyaev-Zeldovich distortions and how they might be measured. The paper is in the folder marked Cosmology and NonGalactic Astrophysics.
Here is a screen grab of the overlay which includes the abstract:
You can click on the image of the overlay to make it larger should you wish to do so. You can find the officially accepted version of the paper on the arXiv here.
The second paper has the title “On the contribution of dwarf galaxies to reionization of the Universe” and is by Zewei Wu and Andrey Kravtsov of the University of Chicago in the USA. This paper, which is in the folder marked Astrophysics of Galaxies, presents a model of galaxy formation that suggests that radiation from very faint galaxies may contribute significantly to the reionization of the Universe.
Here is a screen grab of the overlay which includes the abstract:
You can click on the image of the overlay to make it larger should you wish to do so. You can find the officially accepted version of the paper on the arXiv here.
That concludes this week’s update. No doubt I’ll have more for you next week!
Why Do We Need Simulations for the Euclid Telescope?
Posted in Euclid, The Universe and Stuff with tags Cosmology, Euclid, simulations on June 23, 2024 by telescoperUntil I can get my laptop fixed and/or get a new one, my ability to write blog posts is a bit limited. At least there is a sizeable collection of things to share, including a steady supply of new videos from the Euclid Consortium like this one:
In the Dark 