Archive for the The Universe and Stuff Category

« Older Entries
Newer Entries »

Back to the Office

Posted in Barcelona, Biographical, Maynooth, The Universe and Stuff on June 30, 2025 by telescoper

After a week away in Cork, I’m back in the office at Maynooth University. I have quite a lot of things to do before my next trip away which will be next week.

On Friday (27th) Maynooth students got their examination results. For this year’s finalists that means they also received news of their final degree classification. I’ve seen quite a few celebratory messages flying around on social media so let me add my own congratulations here: Congratulations!

We’ve had an outstanding group of students in Theoretical Physics this year and that is reflected in some excellent degree results. Well done to them all, and best wishes for the further studies on which many of them are about to embark.

Tomorrow (Tuesday 1st July), we have a consultation day during which students can ask about their examinations and request advice on next steps, including repeat examinations in August, the papers for which have to be readied for printing in the next two weeks.

Campus is quiet at this time of year, as most of the undergraduate students have left for the summer (or permanently for the graduands). A few will remain to do summer projects. The postgraduates are still around, of course. I have a Masters student doing their project this summer, from which I hope a paper will emerge, and a PhD student doing post-viva corrections to her thesis. I’ve also got a couple of other papers to finish.

I’m hearing a lot about sweltering temperatures across Europe. Fortunately it is more temperate here in Ireland, with maximum of 23 degrees forecast in Maynooth. All of this reminds me that it was a year ago today that I returned from a spell in Barcelona on sabbatical. As it happens, I met my hosts Licia and Raul at EAS last week. It seems things are going well at ICCUB. I would have stayed longer there, but my laptop had died which left me unable to work effectively. I’m looking forward to visiting there again next year for the 2026 Euclid Consortium meeting (if I can find the time).

1 Comment »

Primordial Black Holes in Cosmological Simulations

Posted in Maynooth, The Universe and Stuff with tags , , on June 29, 2025 by telescoper

Being so busy for the last couple of weeks I omitted to engage in the gratuitous self-promotion that one would expect from a blogger, so I’m remedying that today by pointing out that I’m co-author of a new paper that is now on arXiv. This has already gained a bit of traction in the media, e.g. here.

Here is the abstract, which also shows the author list:

(I’ve just noticed that it says “The Netherland”, instead of “The Netherlands”. Oops!)

For those of you not in the field, there is currently a big mystery about how galaxies we have found at high redshift with JWST managed to acquire massive black holes so early in the Universe’s evolution. Black holes can grow quickly in a dense environment by accreting mass onto an initial seed, but what are the seeds? In this paper we investigate the possibility that they were primordial black holes. These form directly from fluctuations in the early Universe, as opposed to astrophysical black holes which form from stellar collapse. We don’t know exactly what mass primordial black holes would have nor how numerous they would be, but this paper uses high-resolution numerical experiments to investigate their effects if they do exist.

Here’s a pretty picture which is a zoom into 200 pc of the full simulation. I think 10pc counts as high resolution for a cosmological simulation! The blue circle shows the most massive PBH in the simulation, the green circle shows its nearest neighbour. The colour scale represents the number-density of dark matter particles.

For more details, read the paper!

P.S. This article has been submitted to the Open Journal of Astrophysics and is currently under review. As an author I am not involved in the editorial process.

2 Comments »

Weekly Update from the Open Journal of Astrophysics – 28/06/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , , , , , , , , on June 28, 2025 by telescoper

It’s Saturday morning again so time for an update of papers published at the Open Journal of Astrophysics. Since the last update we have published eight new papers, which brings the number in Volume 8 (2025) up to 82, and the total so far published by OJAp  up to 317. With about half the year gone, we’re on target to published around 160 papers this year.

The 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 first paper to report is “Spectroscopic and X-ray Modeling of the Strong Lensing Galaxy Cluster MACS J0138.0-2155” by Abigail Flowers (University of California at Santa Cruz; UCSZ), Jackson H. O’Donnell (UCSZ), Tesla E. Jeltema (UCSZ), Vernon Wetzell (U. Pennsylvania) & M. Grant Roberts (UCSZ). This artticle, which is in the folder marked Cosmology and NonGalactic Astrophysics, presents a study of the mass distribution and substructure of a galaxy cluster that acts as a gravitational lens for a source galaxy at z=1.95 that contains two supernovae. It was published on 23rd June 2025. The overlay is here:

The officially-accepted version can be found on arXiv here.

“Illuminating the Physics of Dark Energy with the Discovery Simulations” by Gillian D. Beltz-Mohrmann (Argonne National Laboratory, USA) and 12 others based in the USA and Spain. This describes new high-resolution cosmological simulations providing a testbed for alternative cosmological probes that may offer additional constraining power beyond Baryon Accoustic Oscillations. It is filed in the folder marked Cosmology and NonGalactic Astrophysics.

The overlay is here:

You can read the final accepted version on arXiv here.

Next one up is in the folder marked Astrophysics of Galaxies. The title is “On the minimum number of radiation field parameters to specify gas cooling and heating functions” and it is by David Robinson & Camille Avestruz (U. Michigan) and Nickolay Y. Gnedin (U.Chicago) and was published on 23rd June 2025. It presents an analysis using machine learning of atomic gas cooling and heating functions computed by the spectral synthesis code Cloudy.

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

The thirtd paper is “On the Use of WGANs for Super Resolution in Dark-Matter Simulations” by John Brennan (Maynooth), Sreedhar Balu (U. Melbourne), Yuxiang Qin (ANU), John Regan (Maynooth) and Chris Power (U. Western Australia). This one is also in the folder marked Astrophysics of Galaxies and was also published on Monday 23rd June. It is about using the Wasserstein Generative Adversarial Network (WGAN) model to increase the particle resolution of dark-matter-only simulations of galaxy formation. The overlay is here:

You can find the officially-accepted version of the paper on arXiv here.

Next we have “Cosmic Rays Masquerading as Hot CGM Gas: An Inverse-Compton Origin for Diffuse X-ray Emission in the Circumgalactic Medium” by Philip F. Hopkins (Caltech), Eliot Quataert (Princeton), Sam B. Ponnada (Caltech) and Emily Silich (Caltech), all based in the USA.  This one was published on 24th June 2025 in the folder High-Energy Astrophysical Phenomena

You can find the officially-accepted version on arXiv here.

The fifth paper this week is “Compact Binary Formation in Open Star Clusters III: Probability of Binary Black Holes Hidden Inside of Gaia Black Hole Binary” by Ataru Tanikawa (Fukui Prefectural University, Japan), Long Wang (Sun Yat-sen University, China), Michiko S. Fujii (University of Tokyo, Japan), Alessandro A. Trani (Niels Bohr Institute, Denmark), Toshinori Hayashi (Kyoto University, Japan) and Yasushi Suto (Kochi University of Technology, Japan).  This one is in the folder marked Astrophysics of Galaxies and was published on Tuesday 24th June. It presents an investigation into whether some Gaia black hole binary systems may in fact involve three black holes, including a pair too compact to be resolved astrometrically. Here is the overlay:

You can find the officially-accepted paper on arXiv here.

Next we have “Rapid identification of lensed type Ia supernovae with color-magnitude selection” by Prajakta Mane (IISER) and Anupreeta More & Surhud More (IUCAA), all based in India. This paper presents an  extension of the use of color-magnitude diagrams, used previously as a means to identify lensed supernovae, with applications to LSST-like photometric data. It is in the folder marked Astrophysics of Galaxies and was published on Thursday 26th June.

The officially-accepted version of the article can be found on arXiv here.

The penultimate article this week is: “Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization” by Huanqing Chen (U. Alberta, Canada), and Jiawen Fan & Camille Avestruz (U. Michigan, USA). This one is in the folder Cosmology and Nongalactic Astrophysics and was published on 26th June 2025.  This paper studies possible systematic effects in computer simulations of cosmic reionization especially when it results from quasar radiation.

The overlay is here:

You can find the officially-accepted version on arXiv here.

Eighth and last paper this week is “Exploring the Core-galaxy Connection” by Isabele Lais de Souza Vitório (U. Michigan) and Michael Buehlmann, Eve Kovacs, Patricia Larsen, Nicholas Frontiere & Katrin Heitmann (Argonne National Laboratory, USA).  This one is in the folder Cosmology and Nongalactic Astrophysics and was published on Friday 27th June 2025 (i.e. yesterday).

The overlay is here:

 

You can find the officially-accepted version on arXiv here.

And that’s all the papers for this week. I do, however, have some more news to pass on. We are delighted to welcome two new recruits to our Editorial Board,  Dr Foteini Oikonomou of the Norwegian University of Science and Technology, who specializes in the application of particle physics theories to  high-energy astrophysical phenomena, and Dr Heloise Stevance of Oxford University (UK), who specializes in the interface between Machine Learning and Astrophysics.

1 Comment »

Wednesday at #EAS2025

Posted in Biographical, Euclid, The Universe and Stuff with tags , , , , on June 25, 2025 by telescoper

I spent most of today at the EAS 2025 sessions about Euclid. These were mainly about the Q1 data release I blogged about here, although there were some talks about what to expect about the first full data release (DR1), which is due towards the end of next year (2026), before I retire.

There were three Euclid sessions, one in the morning and two in the afternoon; I’m writing this during the last of these.

I was reminded this morning that the word “plenary” is derived from the Latin plenus, meaning “full”. This explains why there are no free seats for the plenary session, so I had to watch the stream in one of the overflow theatres.

I also attended a lunchtime session about the Square Kilometre Array Observatory (SKAO). This was interesting, though the first full data release from SKAO will not happen until after I’ve retired.

And, to end the day, I’m at a reception and meeting of SKA Ireland, a group campaigning for Ireland to join the SKAO.. There’s win.

1 Comment »

Tuesday at #EAS2025

Posted in Open Access, The Universe and Stuff with tags , , , on June 24, 2025 by telescoper

Today was my first day at EAS 2025 on the nice campus of University College Cork. I managed to register before the first session and found my way around what is clearly a very well organised meeting. They have a very useful app to help attendees navigate both space and time.

I spent a large part of today at a session about the future of scientific publishing,  which was split in two, either side of the morning’s plenary. The first half started with a talk by Selina La Barbera, a representative of EDP Sciences, the publisher of the journal Astronomy and Astrophysics:

It also featured a talk by João Alves, Letters Editor of Astronomy and Astrophysics, and Uta Grothkopf, librarian of the European Southern Observatory. The last talk was full of insights and information. The Q&A was very lively. I was expecting that I might be the one to inject some controversy into the discussion, but I didn’t need to. Issues about the cost of APCs, etc, were raised by others before I got the chance.

Before the plenary, there was time for a group photograph of staff and students from Maynooth:

The Maynooth Contingent

The highlight of the plenary was seeing Licia Verde collect the Jocelyn Bell Burnell Medal on behalf of arXiv, together with Ralph Wijers. They both gave interesting presentations about arXiv too.

Licia, with the EAS Medal she received today.

Back in the special session about publishing, I participated in a panel discussion, which was very lively. On a Zoom  call last week in preparation for this, we were a bit worried that not many people would take part, but in the event the room was full and many people asked questions, including many about OJAp, and the discussion went on outside after the session was finished.  I think it was a very successful session.

Now that the session I was directly involved in is over, I can relax a bit and be free tomorrow to  attend more science sessions, including a couple about Euclid…

1 Comment »

Vera C. Rubin Observatory “First Look” Images

Posted in The Universe and Stuff with tags , , , on June 23, 2025 by telescoper

Just a quick note to say that the “first look” images from the Vera C. Rubin Observatory will be revealed at 11am (Eastern Daylight Time; 4pm local Irish Time). This is the live stream:

I understand there will be a watch party at the EAS meeting in Cork, but I will be on the train so I’ll miss it.

A few images have been released already as a sneak preview. Here is one, to whet your appetitite:

This image shows a small section of NSF-DOE Vera C. Rubin Observatory’s total view of the Virgo cluster.
Image by NSF-DOE Vera C. Rubin Observatory

Leave a comment »

Summer Solstice 2025

Posted in Irish Language, The Universe and Stuff with tags , , , , on June 21, 2025 by telescoper

In case you weren’t aware, the Summer Solstice in the Northern hemisphere took place this morning Saturday June 21, 2025 at 02:42 UTC (03:42am local Irish Time). Among other things, this means that today is the longest day of the year (as defined by the interval between sunrise and sunset).

According to this website, the interval between sunrise and sunset in Dublin today will be 17 hours and 12 seconds. which is a whole second longer than yesterday (!) and six seconds longer than tomorrow.

In the Northern hemisphere, days will get shorter from the Summer Solstice until the Winter Solstice in December.

The nights are drawing in. Although sunset does carry on getting a bit later for a few days, the days definitely start getting shorter from now on. I explained this in earlier posts here.

Incidentally, the word for “solstice” in the Irish language is grianstad which translates literally as “sun-stop”. The Summer Solstice is Grianstad an tSamhraidh“. The nominative singular word for “Summer”, a masculine noun in Irish, is Samhradh, but in the construction used here, “of summer”, it is in the genitive case so becomes Samhraidh. Moreover, when a masculine noun beginning with s- in the singular genitive is preceded by the definite article an) it experiences an initial mutation in the form of a t-prothesis; hence (an tSamraidh is “of the Summer”.

The Winter Solstice is Grianstad an Gheimhridh. The word for winter is Geimhreadh, which is masculine, and has a genitive form Geimhridh. In this case, however, because it doesn’t begin with “S” there is no t-prothesis but instead a lenition (séimhiú) that softens the initial “G” indicated by the “h”. Hence Grianstad an Gheimhridh, “Sun-stop of the Winter”.

I hope this clarifies the situation.

4 Comments »

Weekly Update from the Open Journal of Astrophysics – 20/06/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , on June 20, 2025 by telescoper

Yesterday (Thursday 19th June 2025) was a national holiday in the USA, which means that no new papers were announced on arXiv today (Friday 20th June). I have therefore decided to bring forwarded the usual weekly update of papers published at the Open Journal of Astrophysics by a day. Since the last update we have published three new papers, which brings the number in Volume 8 (2025) up to 74, and the total so far published by OJAp  is now up to 309.

The three papers published this week, with their overlays, are as follows. All three were published on Tuesday, June 17th 2025. You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is “Illuminating the Physics of Dark Energy with the Discovery Simulations” by Gillian D. Beltz-Mohrmann (Argonne National Laboratory, USA) and 12 others based in the USA and Spain. This describes new high-resolution cosmological simulations providing a testbed for alternative cosmological probes that may offer additional constraining power beyond Baryon Accoustic Oscillations. It is filed in the folder marked Cosmology and NonGalactic Astrophysics.

The overlay is here:

You can read the final accepted version on arXiv here.

The second paper is in the folder marked Astrophysics of Galaxies. It is “LIGHTS. The extended point spread functions of the LIGHTS survey at the LBT” by Nafise Sedighi (Instituto de Astrofísica de Canarias, Spain) and 15 others based in Spain, USA, Iran, Italy and the UK. It describes the procedure used to construct the extended Point Spread Functions (PSFs) of the LIGHTS survey in images taken with the Large Binocular Cameras (LBCs) of the Large Binocular Telescope (LBT).

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

Finally this week we have “Fast radio bursts as a probe of gravity on cosmological scales” by Dennis Neumann (Leiden University, Netherlands), Robert Reischke (Universität Bonn, Germany), Steffen Hagstotz (Ludwig-Maximilians Universität München, Germany) and Hendrik Hildebrandt (Ruhr University Bochum, Germany). This is about using dispersion measures derived from Fast Radio Bursts (FRBs) in combination with cosmic shear to investigate modified gravity theories, specifically Horndeski gravity. It is in the folder marked Cosmology and NonGalactic Astrophysics.

The overlay is here:

You can find the officially-accepted version on arXiv here.

That’s all the papers for this week. I’ll revert to the usual schedule for updates next week, and post the next one on Saturday 28th June.

 

1 Comment »

Weekly Update from the Open Journal of Astrophysics – 14/06/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , on June 14, 2025 by telescoper

It’s Saturday so once again it’s time for the weekly update of papers published at the Open Journal of Astrophysics. Since the last update we have published two new papers, which brings the number in Volume 8 (2025) up to 71, and the total so far published by OJAp  is now up to 306.

The two 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 first paper to report is “Analysis of optical spectroscopy and photometry of the type I X-ray bursting system UW CrB2” by Mark Kennedy (University College Cork, Ireland) and 21 others based in Ireland, UK, USA, Finland, Netherlands and Australia. This one was published on Tuesday June 10th in the folder High-Energy Astrophysical Phenomena.  This describes optical photometry and spectroscopy of the low-mass X-ray binary UW Coronae Borealis taken over 2 years

The overlay is here:

 

 

You can read the final accepted version on arXiv here.

The second paper is “The Impact of Feedback-driven Outflows on Bar Formation” by Martin D. Weinberg (University of Massachusetts, Amherst, USA). This paper uses a generalization of the Hamiltonian Mean-Field model to of the disruption of bar formation in galaxies by stellar feedback. It was published on Friday 13th June 2025 in the folder marked Astrophysics of Galaxies.

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

That’s all the papers for this week. I’ll post another update next weekend.

 

1 Comment »

The magnetic moment of the muon revisited

Posted in The Universe and Stuff with tags , , , , on June 10, 2025 by telescoper

A couple of years ago I posted an item about a measurement of the anomalous magnetic moment of the muon, a quantity usually known as (g-2). At the time this appeared to be in conflict with the predictions of the standard model (SM)of particle physics but the general opinion among experts was that the problem was likely to lie with the calculations rather than the experiment.

Well, catching up on things I missed during examination marking season, I refer you to a substantial paper (188 pages long) that appeared on arXiv on 27th May 2025, with the abstract:

If this is too small to read I direct yourself to the salient point, namely that “there is no tension between the SM and experiment at the current level of precision”.

It seems the Standard Model survives to fight another day…

Leave a comment »

« Older Entries
Newer Entries »