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Two New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , on September 7, 2024 by telescoper

It’s Saturday morning again so here’s another report on activity at the  Open Journal of Astrophysics.  Since the last update we have published two more papers, taking  the count in Volume 7 (2024) up to 73 and the total published by OJAp up to 188.  We’ve still got a few in the pipeline waiting for the final versions to appear on arXiv so I expect we’ll reach the 200 mark fairly soon.

The first paper of the most recent pair, published on September 4th 2024,  and in the folder marked Astrophysics of Galaxies, is “Massive Black Hole Seeds”  by John Regan of the Department of Theoretical Physics at Maynooth University and Marta Volonteri (Sorbonne Université, Paris, France). This article presents a discussion of the pathways to the formation of massive black holes, including both light and heavy initial seeds.

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. Those of you who are paying attention will see that there is a bit of a glitch on the left hand side where software has thrown a line break in between the two author names. I have no idea what caused this so I raised a ticket with Scholastica and no doubt it will soon be fixed.  (Update: it is now fixed, 12th September 2024). You can find the officially accepted version of this paper on the arXiv here.

The second paper has the title “The future of cosmological likelihood-based inference: accelerated high-dimensional parameter estimation and model comparison” and was published on 5th September 2024. The authors are Davide Piras (Université de Genève), Alicja Polanska (MSSL) , Alessio Spurio Mancini (Royal Holloway, London), Matthew A. Price(UCL) & Jason D. McEwen (UCL); the latter four are all based in the UK. This paper, which is in  the folder marked Cosmology and NonGalactic Astrophysics, describes an accelerated approach to Bayesian inference in higher-dimensional settings, as required for cosmology, based on recent developments in machine learning and its underlying technology.

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. More  next week!

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The Editorial Board of the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff with tags , , on September 6, 2024 by telescoper

A couple of months ago, I issued a call for new Editors of the Open Journal of Astrophysics. That was very successful and we added a number of new Editors. The complete list (of 20 members) follows:

Peter Coles* (Department of Theoretical Physics, Maynooth University, Ireland). Cosmology, astrophysics, statistics and methodology.

Thierry Appourchaux (CNRS, Institut d’Astrophysique Spatiale, Orsay, France). Space instrumentation, astroseismology, helioseismology, statistics and methodology.

Emory (Ted) Bunn (Department of Physics, University of Richmond, USA). Relativity, cosmology.

Walter Dehnen (Astronomisches Rechen-Institut, University of Heidelberg, Germany). Stellar dynamics, galaxy dynamics, galaxies, bars, Milky-Way dynamics, Gaia, numerical methods, N-body techniques, smooth particle hydrodynamics (SPH).

Philipp Edelmann (Los Alamos National Laboratory, New Mexico, USA). Stellar astrophysics, hydrodynamics, high-performance computing, supernovae, internal waves, stellar evolution, numerical methods.

Pedro Ferreira (Department of Physics, University of Oxford, UK). Large-scale structure, general relativity, cosmic microwave background, early universe, cosmology.

Andrew Jaffe (Department of Physics, Imperial College, London, UK). Astrophysics, statistics and methodology, cosmology.

Harley Katz (Department of Astronomy and Astrophysics, University of Chicago, USA). Galaxy formation and evolution, numerical simulations

Lucyna Kedziora-Chudczer (School of Physics, University of New South Wales, Sydney, Australia). Active galactic nuclei, polarimetry, atmospheres of planets, exoplanets, solar system planets.

Julien Larena (Laboratoire Univers et Particules de Montpellier, Université de Montpellier, France). Cosmology, gravitation, lensing, large-scale structure, general relativity.

Manuela Magliocchetti (National Institute of Astrophysics, Rome, Italy). Cosmology, galaxies, active galactic nuclei (AGN).

Sean McGee (Department of Physics & Astronomy, University of Birmingham, UK). Galaxy formation, galaxy clusters, galaxy surveys.

Manolis Plionis (Department of Physics, Aristotle University of Thessaloniki, Greece). Observational cosmology, extragalactic astrophysics, large-scale structure, active galactic nuclei.

Alkistis Pourtsidou (Higgs Centre & Institute for Astronomy, Edinburgh, UK). Cosmology, large-scale structure of the Universe, radio astronomy, galaxy surveys.

Justin Read (School of Mathematics and Physics, University of Surrey, UK). Dark matter, cosmology, galaxy formation and evolution, dwarf galaxies, milky way, galactic dynamics, galactic archaeology, computational modeling.

Hanno Rein (Department of Physics and Environmental Sciences, University of Toronto at Scarborough, Canada). Numerical methods, in particular N-body codes and integration methods for planetary systems, planet formation, stochastic processes, planet migration, celestial mechanics, and Saturn’s rings.

Aleks Scholz (School of Physics & Astronomy, University of St Andrews, UK). Exoplanets, brown dwarfs, protoplanetary disks, stellar evolution, star formation.

Elena Sellentin (Sterrewacht Leiden, Leiden University, The Netherlands). Applied Mathematics, Cosmology, Statistics, Statistical Inference.

Elena Terlevich (Instituto Nacional de Astrofísica, Óptica y Electrónica, Puebla, Mexico). Stellar populations in galaxies, observational cosmology, violent star formation, element abundances, dynamics of stellar systems.

Bingbing Wang (Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, USA.) Particle astrophysics, MHD turbulence, cosmic rays acceleration, cosmic ray propagation in the Galaxy and heliosphere.

Apologies to anyone who volunteered but has not yet received a reply from me. I’ve been a bit preoccupied these last weeks! The call is still open, though. Here are the areas of arXiv covered by the journal:

  1. astro-ph.GA – Astrophysics of Galaxies. Phenomena pertaining to galaxies or the Milky Way. Star clusters, HII regions and planetary nebulae, the interstellar medium, atomic and molecular clouds, dust. Stellar populations. Galactic structure, formation, dynamics. Galactic nuclei, bulges, disks, halo. Active Galactic Nuclei, supermassive black holes, quasars. Gravitational lens systems. The Milky Way and its contents
  2. astro-ph.CO – Cosmology and Nongalactic Astrophysics. Phenomenology of early universe, cosmic microwave background, cosmological parameters, primordial element abundances, extragalactic distance scale, large-scale structure of the universe. Groups, superclusters, voids, intergalactic medium. Particle astrophysics: dark energy, dark matter, baryogenesis, leptogenesis, inflationary models, reheating, monopoles, WIMPs, cosmic strings, primordial black holes, cosmological gravitational radiation
  3. astro-ph.EP – Earth and Planetary Astrophysics. Interplanetary medium, planetary physics, planetary astrobiology, extrasolar planets, comets, asteroids, meteorites. Structure and formation of the solar system
  4. astro-ph.HE – High Energy Astrophysical Phenomena. Cosmic ray production, acceleration, propagation, detection. Gamma ray astronomy and bursts, X-rays, charged particles, supernovae and other explosive phenomena, stellar remnants and accretion systems, jets, microquasars, neutron stars, pulsars, black holes
  5. astro-ph.IM – Instrumentation and Methods for Astrophysics. Detector and telescope design, experiment proposals. Laboratory Astrophysics. Methods for data analysis, statistical methods. Software, database design
  6. astro-ph.SR – Solar and Stellar Astrophysics. White dwarfs, brown dwarfs, cataclysmic variables. Star formation and protostellar systems, stellar astrobiology, binary and multiple systems of stars, stellar evolution and structure, coronas. Central stars of planetary nebulae. Helioseismology, solar neutrinos, production and detection of gravitational radiation from stellar systems.

We are looking for experienced scientists in any of these areas, and it would indeed be useful to have people who can cover a range of subjects (as some of our existing editors do), but there I think we’re still a bit short on High-Energy Astrophysics, Solar and Stellar Physics, and Galactic Astrophysics. I’d also like to see a better gender balance so applications from female scientists are particularly welcomed, as are astrophysicists from geographical areas not currently covered. The Open Journal of Astrophysics is intended to be a global enterprise!

Please follow the instructions here if you would like to volunteer!

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Prize Poster!

Posted in Maynooth, The Universe and Stuff with tags , , , , , on September 1, 2024 by telescoper

I had been looking forward to attending last week’s Irish National Astronomy Meeting in the fine city of Galway but unfortunately I couldn’t go because I had an appointment I couldn’t reschedule (which also kept me offline for a couple of days). This was a shame because it turns out that one of our undergraduate SPUR students at Maynooth, Jake Feeney, together with two colleagues, John Regan and Paddy Kavanagh, won the prize for the best poster at INAM.

Here is the winning poster:

Congratulations to Jake et al!

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Two New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , on August 31, 2024 by telescoper

I am back in circulation after my little break and, since it’s Saturday, I will resume blogging with another report on activity at the  Open Journal of Astrophysics.  Since the last update we have published two more papers, taking  the count in Volume 7 (2024) up to 71 and the total published by OJAp up to 186.  We’ve still got a few in the pipeline waiting for the final versions to appear on arXiv so I expect we’ll reach the 200 mark fairly soon.

The first paper of the most recent pair, published on August 26th 2024,  is “Impact of lensing of gravitational waves on the observed distribution of neutron star masses”  by Sofia Canevarolo, Loek van Vonderen and Nora Elisa Chisari, all of Utrecht University in the Netherlands. This article presents a discussion of the bias in neutron star mass determinations caused by gravitational lensing of the gravitational waves they produceThe 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 “FORGE’d in FIRE III: The IMF in Quasar Accretion Disks from STARFORGE” and was published (in the early hours of the morning) on 29th August 2024. The authors, all based in the USA, are Philip F. Hopkins (Caltech), Michael Y. Grudic (Carnegie Observatories), Kyle Kremer (Caltech), Stella S. R. Offner (UT Austin), David Guszejnov (UT Austin) and Anna L. Rosen (UCSD). This paper, which is in the folder marked Astrophysics of Galaxies, presents a numerical study of star formation and the initial mass function in quasar accretion disks. The previous two papers in this series have also been published in the OJAp: you can find them here and here; images and movies related to this project can be found here.

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. We still have quite a few papers in the pipeline after the summer lull so I expect I’ll have a larger update for you next week!

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Coming of Age in a Low-Density Universe

Posted in Biographical, Open Access, The Universe and Stuff with tags , , , , on August 25, 2024 by telescoper

I was reminded just now that 30 years ago today, on 25th August 1994, this review article by myself and George Ellis was published in Nature (volume 370, pp. 609–615).

Sorry for the somewhat scrappy scanned copy. The article is still behind a paywall. No open access for the open Universe!

Can this really have been 30 years ago?

Anyway, that was the day I officially became labelled a “crank”, by some, although others thought we were pushing at an open door. We were arguing against the then-standard cosmological model (based on the Einstein – de Sitter model), but the weight of evidence was already starting to shift. Although we didn’t predict the arrival of dark energy, the arguments we presented about the density of matter did turn out to be correct. A lot has changed since 1994, but we continue to live in a Universe with a density of matter much lower than the critical density and our best estimate of what that density is was spot on.

Looking back on this, I think valuable lessons would be learned if someone had the time and energy to go through precisely why so many papers at that time were consistent with a higher-density Universe that we have now settled on. Confirmation bias undoubtedly played a role, and who is to say that it isn’t relevant to this day?

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New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , on August 24, 2024 by telescoper

It’s Saturday morning so it’s time for the usual weekly update of publications at the Open Journal of Astrophysics. Once again this week’s report will be short because there is only one paper to report this week, being  the 69th paper in Volume 7 (2024)  and the 184th  altogether. It was published on Wednesday 21st August 2024.

This week has been a bit strange, actually. We have actually accepted four papers that I was expecting to publish this week but only one has been published because the authors of the others have not yet put the final versions on arXiv. I suppose this is due to ongoing holidays and they’ll appear in due course. The other thing that happened was that when I published the paper below I discovered that the Crossref system was down for a scheduled upgrade that took a whole day to complete. Although I published the paper on 21st August I couldn’t register the metadata, etc, until 22nd August. Just as well I didn’t have more to do really!

Anyway, the title of the latest paper is is The compact circumstellar material of SN 2024ggi: another supernova with a pre-explosion effervescent zone and jet-driven explosion and it  is in the folder marked High-Energy Astrophysical Phenomena. The author is Noam Soker of Technion, Haifa, in Israel; the paper presents a possible explanation of then properties of recently-observed supernova SN 2024ggi.

Here is the overlay of the paper containing the abstract:

 

 

You can click on the image of the overlay to make it larger should you wish to do so. You can also find the officially accepted version of the paper on the arXiv here.

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Newgrange and JWST

Posted in History, The Universe and Stuff with tags , , on August 18, 2024 by telescoper

Although I won’t myself be able to attend, I’m happy to be able to use the medium of this blog to advertise the above public event which is taking place in the first week of September on the back of a week-long conference to celebrate the career of Professor Tom Ray of the Dublin Institute for Advanced Studies. That in turn follows hard on the heels of the Irish National Astronomy Meeting (INAM) which takes place in Galway on 29th and 30th August.

Anyway, the public event on 3rd September is free to attend but you need to register here, where it is described thusly:

The Newgrange Passage Tomb, a prehistoric monument in County Meath, Ireland, is one of the most remarkable examples of Neolithic art and architecture, dating back to around 3200 BC. This ancient structure, with its intricate stone carvings and precise alignment with the winter solstice sunrise, reflects the sophisticated astronomical knowledge of its builders.

With starkly different technology, the James Webb Space Telescope (JWST), launched in 2021, represents the pinnacle of modern astronomical achievement. JWST is designed to peer into the farthest reaches of the universe, capturing images and data from the formation of the earliest galaxies to the atmospheres of planets outside of/beyond our solar system.

Despite being separated by millennia, both Newgrange and JWST underscore humanity’s enduring quest to understand our place in the cosmos through the study of the stars and the universe.

As part of the celebration of the career of Professor Tom Ray the Dublin Institute for Advanced Studies and the Institute of Physics are delighted to host a public event on Newgrange and JWST. This is in recognition of Tom’s long interest in archaeoastronomy and Newgrange in particular, and his involvement with the JWST through the Mid-Infrared instrument (MIRI).

The talk will be delivered by Dr. Frank Prendergast, archaeoastronomer and Emeritus Research Fellow at Technological University Dublin, and Professor Gillian Wright, European Principal Investigator of MIRI and Director of the UK Astronomy Technology Centre in Edinburgh.

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New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , on August 17, 2024 by telescoper

It’s Saturday morning and time for the usual weekly update of publications at the Open Journal of Astrophysics. This will be a short post because there is only one paper to report this week, being  the 68th paper in Volume 7 (2024)  and the 183rd  altogether. It was published on Thursday August 15th 2024.

The title of the latest paper is is “Spatial segregation of massive clusters in a simulation of colliding dwarf galaxies” and it  is in the folder marked Astrophysics of Galaxies. The authors are Bruce Elmegreen (IBM, NY, USA) and Natalia Lahen (MPA Garching, Germany);  the paper presents a numerical study of the properties and spatial distribution of star clusters resulting from a collision between dwarf galaxies.

Here is the overlay of the paper containing the abstract:

 

 

You can click on the image of the overlay to make it larger should you wish to do so. You can also find the officially accepted version of the paper on the arXiv here.

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Evolving Dark Energy or Supernovae Systematics?

Posted in The Universe and Stuff with tags , , , , , , , on August 15, 2024 by telescoper

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.

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Hubble Tension Reduced?

Posted in The Universe and Stuff with tags , , , , on August 14, 2024 by telescoper

Back in April I posted about a meeting at the Royal Society in London called Challenging the Standard Cosmological Model, some of which I attended virtually. In that post I mentioned that Wendy Freedman gave a talk related to the ongoing issue of the Hubble Tension, i.e. the discrepancy between different types of measurement of the Hubble Constant, usually characterized as local measurements (using stellar distance indicators) and larger-scale measurements (chiefly Planck). There are quite a few posts about this issue on this blog. Anyway, Wendy Freedman mention in her talk that her latest work on stellar distances suggested a value of 69.1 ± km s-1 Mpc-1, which reduces the tension with Planck significantly. At the time, however, there was no paper explaining how this number was derived.

Yesterday there appeared on arXiv a preprint by Freedman et al. which summarizes the recent results. The abstract is here:

We present the latest results from the Chicago Carnegie Hubble Program ( CCHP) to measure the Hubble constant using data from the James Webb Space Telescope (JWST). This program is based upon three independent methods: (1) Tip of the Red Giant Branch (TRGB) stars, (2) JAGB (J-Region Asymptotic Giant Branch) stars, and (3) Cepheids. Our program includes 10 nearby galaxies, each hosting Type Ia supernovae (SNe Ia), suitable for measuring the Hubble constant (H0). It also includes NGC  4258, which has a geometric distance, setting the zero point for all three methods. The JWST observations have significantly higher signal-to-noise and finer angular resolution than previous observations with the Hubble Space Telescope (HST). We find three independent values of H0 = 69.85 ± 1.75 (stat) ± 1.54 (sys) for the TRGB, H0 = 67.96 ± 1.85 (stat) ± 1.90 (sys)  km s-1 Mpc-1 for the JAGB, and H0 = 72.05 ± 1.86 (stat) ± 3.10 (sys) for Cepheids. Tying into SNe Ia, and combining these methods adopting a flat prior, yields our current estimate of H0 = 69.96 ± 1.05 (stat) ± 1.12 (sys)  km s-1 Mpc-1. The distances measured using the TRGB and the JAGB method agree at the 1% level, but differ from the Cepheid distances at the 2.5-4% level. The value of H0 based on these two methods with JWST data alone is H0 = 69.03 ± 1.75 (total error)  km s-1 Mpc-1. These numbers are consistent with the current standard ΛCDM model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.

You can read the full paper on arXiv here. A summary of the summary is that of the three methods they use, two give lower values of the Hubble constant and one (Cepheids) gives a higher value but with larger errors. The number quoted in the Royal Society talk was presumably preliminary as it doesn’t match any of the numbers in the abstract, but the point remains.

You can see the reduction in scatter in the new JWST measurements in this Figure (old on the left and new on the right).

On the face of it, these results suggest that the Hubble tension is greatly reduced. I am sure, however, that advocates of a higher value will have been preparing their ripostes and it’s just a matter of time before they arrive on the arXiv too!

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