Archive for the The Universe and Stuff Category

String theory lied to us and now science communication is hard…

Posted in mathematics, The Universe and Stuff with tags , , on April 30, 2023 by telescoper

Taking the opportunity of the Bank Holiday weekend to catch up on some other blogs, I found this video on Peter Woit’s Not Even Wrong. It’s by Angela Collier. It’s a bit long for what it says, and I find the silly game going on while the speaker talks very irritating, but the speaker makes some very good points and it’s well worth watching all the way through. The most important message it conveys, I think, is how the hype surrounding string theory contributed to increasing public distrust of science and the media.

If I were a string theorist I probably wouldn’t appreciate this video, but I’m not and I do!

No Tension at Redshift Ten

Posted in Maynooth, The Universe and Stuff with tags , , , , , on April 29, 2023 by telescoper

I know it’s the Bank Holiday weekend but I could resist a quick post about a new paper that hit the arXiv yesterday (where all new astrophysics papers worth reading can be found). It is led by Joe McCaffrey who is a PhD student in the Department of Theoretical Physics at Maynooth University. The paper has been submitted to the Open Journal of Astrophysics, but obviously I am conflicted so have assigned it to another editor.

UPDATE: the paper is now published here.

As many of you will be aware, there’s been a considerable to-do not to mention a hoo-hah about the detections by JWST of some galaxies at high redshift. Some of these have been shown not to be galaxies at high redshift after all, but some around z=10 seem to be genuine.

Anyway, the abstract of Joe’s paper is this:

Recent observations by JWST have uncovered galaxies in the very early universe via the JADES and CEERS surveys. These galaxies have been measured to have very high stellar masses with substantial star formation rates. There are concerns that these observations are in tension with the ΛCDM model of the universe, as the stellar masses of the galaxies are relatively high for their respective redshifts. Recent studies have compared the JWST observations with large-scale cosmological simulations. While they were successful in reproducing the galaxies seen in JADES and CEERS, the mass and spatial resolution of these simulations were insufficient to fully capture the early assembly history of the simulated galaxies. In this study, we use results from the Renaissance simulations, which are a suite of high resolution simulations designed to model galaxy formation in the early universe. We find that the most massive galaxies in Renaissance have stellar masses and star formation rates that are entirely consistent with the observations from the JADES and CEERS surveys. The exquisite resolution afforded by Renaissance allows us to model the build-up of early galaxies from stellar masses as low as 104 M⊙ up to a maximum stellar mass of a few times 107 M⊙. Within this galaxy formation paradigm, we find excellent agreement with JADES and CEERS. We find no tension between the ΛCDM model and current JWST measurements. As JWST continues to explore the high redshift universe, high resolution simulations, such as Renaissance, will continue to be crucial in understanding the formation history of early embryonic galaxies.

arXiv:2304.13755

The key figure is this one:

The solid curves show the number of galaxies of a given mass one would expect to see as a function of redshift in fields comparable to those observed with estimated values from observations (star-shaped symbols). As you can see the observed points are consistent with the predictions. There’s no tension, so you can all relax.

New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, The Universe and Stuff with tags , , , , on April 28, 2023 by telescoper

Time for the announcement of yet another new paper at the Open Journal of Astrophysics. The latest paper is the 14th paper so far in Volume 6 (2023) and the 79th in all. This one is in the folder marked Astrophysics of Galaxies and its title is “Massive Star Formation in Overdense Regions of the Early Universe”. The early Universe aspect does of course imply considerable overlap with cosmology.

The (sole) author is our very own John Regan of the Department of Theoretical Physics at Maynooth University.

Here is a screen grab of the overlay which includes the  abstract:

Here’s a bigger version of the image I chose for the overlay:

 

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.

A proto-cluster at z ~ 8!

Posted in The Universe and Stuff with tags , , , , on April 26, 2023 by telescoper
Blow-ups of the seven galaxies with spectroscopic redshifts, shown together with their positions near the line of sight to a foreground cluster.

I missed the paper containing this impressive picture when it first appeared on the arXiv, the primary source for astrophysics and cosmology research, but fortunately it has now been published on a secondary site, Astrophysical Journal Letters, with an accompanying press release so I can now do a quick post about it.

The article concerned, with lead author Takahiro Morishita of the California Institute of Technology (Caltech) et al. describes the detection using JWST of an apparent proto-cluster – seven galaxies in close proximity – at redshift z = 7.88. Here is the abstract:

Although only seven galaxies are identified, this does look like the very early stages of formation of an object that will grow into a giant galaxy cluster by the present epoch. The redshift of this progenitor corresponds to a stage of the Universe just 650 million years or so after the Big Bang, compared with the current age of about 14 billion years. As the abstract says, we would need to know more about other possible constituent galaxies and their motions to be sure, but it looks like a baby destined to grow into a monster…

Euclid Launch Window Update!

Posted in Euclid, The Universe and Stuff with tags on April 26, 2023 by telescoper

(The Euclid spacecraft will be launched via SpaceX on a Falcon 9 rocket from Cape Canaveral in July 2023, but no further details are publicly available right now.)

New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , , , on April 25, 2023 by telescoper

It’s time once more to announce a new paper at the Open Journal of Astrophysics. The latest paper is the 13th paper so far in Volume 6 (2023) and the 78th in all. This one is another for the folder marked Cosmology and NonGalactic Astrophysics and its title is “The catalog-to-cosmology framework for weak lensing and galaxy clustering for LSST”.

The lead author is Judit Prat of the University of Chicago (Illinois, USA) and there are 21 co-authors from elsewhere in the USA and in the UK. The paper is written on behalf of the LSST Dark Energy Science Collaboration (LSST DESC), which is the international science collaboration that will make high accuracy measurements of fundamental cosmological parameters using data from the Rubin Observatory Legacy Survey of Space and Time (LSST). The OJAp has published a number of papers involving LSST DESC, and I’m very happy that such an important consortium has chosen to publish with us.

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.

Astronomy Plot of the Week

Posted in The Universe and Stuff with tags , , on April 19, 2023 by telescoper

Pictures made by observational astronomers, like the one I featured a couple of days ago, often feature on various sites as “Astronomy Pic of the Week” or such. I’ve often thought that this disadvantages astrophysicists of the more theoretical sort and wondered why don’t we do same with graphical illustrations of other kinds. On that basis, I offer this (found here) as my inaugural Astrophysics Plot of the Week:

Its explanatory power is matched by its simplicity and elegance.

New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , on April 18, 2023 by telescoper

Back after a short hiatus due to the Easter holidays, it’s time to announce yet another new paper at the Open Journal of Astrophysics. This one was accepted for publication a few weeks ago but the final version only appeared on the arXiv yesterday. Since OJAp is an arXiv-overlay journal, we have to wait for authors to upload the accepted version before we can publish the overlay.

Anyway, the latest paper is the 12th paper so far in Volume 6 (2023) and the 77th in all. This one is in the currently under-populated folder marked Solar and Stellar Astrophysics and its title is “Predicting Stellar Mass Accretion: An Optimized Echo State Network Approach in Time Series Modeling”.

The authors are: Gianfranco Bino, Shantanu Basu & Ramit Dey (all at the University of Western Ontario, Canada), Sayantan Auddy (Jet Propulsion Laboratory, Pasadena, USA), Lyle Muller (University of Western Ontario, Canada) and Eduardo I. Vorobyov (University of Vienna, Austria & Southern Federal University, Russia).

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.

Maynooth Astronomy Picture of the Week!

Posted in Maynooth, The Universe and Stuff with tags , , , , on April 17, 2023 by telescoper
“A Stellar Sprinkler”

I think for the first time, Maynooth astronomers have been featured in the European Space Agency’s Picture of the Week. Here is the blurb from ESO:

–o–

This Picture of the Week shows the young stellar object 244-440 in the Orion Nebula observed with ESO’s Very Large Telescope (VLT) –– the sharpest image ever taken of this object. That wiggly magenta structure is a jet of matter launched close to the star, but why does it have that shape?

Very young stars are often surrounded by discs of material falling towards the star. Some of this material can be expelled into powerful jets perpendicularly to the disc. The S-shaped jet of 244-440 suggests that what lurks at the center of this object isn’t one but two stars orbiting each other. This orbital motion periodically changes the orientation of the jet, similar to a water sprinkler. Another possibility is that the strong radiation from the other stars in the Orion cloud could be altering the shape of the jet.

These observations, presented in a new paper led by Andrew Kirwan at Maynooth University in Ireland, were taken with the Multi Unit Spectroscopic Explorer (MUSE) instrument at ESO’s VLT in Chile. Red, green and blue colours show the distribution of iron, nitrogen and oxygen respectively. But this is just a small fraction of all the data gathered by MUSE, which actually takes thousands of images at different colours or wavelengths simultaneously. This allows astronomers to study not only the distribution of many different chemical elements but also how they move. 

Moreover, MUSE is installed at the VLT’s Unit Telescope 4, which is equipped with an advanced adaptive optics facility that corrects atmospheric turbulence, delivering images sharper than Hubble’s. These new observations will therefore allow astronomers to study with unprecedented detail how stars are born in massive clouds like Orion.

–o–

There’s also a little video showing how the picture was made using MUSE:

Congratulations to Andrew Hirwan and supervisor Emma Whelan from the Department of Experimental Physics for this coup!

The Cyclic Universe of the UK Astronomy Grant System

Posted in Biographical, Science Politics, The Universe and Stuff with tags , , , on April 17, 2023 by telescoper

I stumbled by accident yesterday on a bit of news relating to UK Astronomy Grant funding via the Science and Technology Facilities Council (STFC). I am of course completely out of that system, and have been for years, but I am nevertheless quite nosy so was interested to find out about the changes. Thanks to Alan Heavens and Paul Crowther for enlightening me.

Way back in 2010 I wrote in somewhat critical terms about the new-style Consolidated Grants that STFC was planning to introduce. This system replaced a dual approach of so-called “Standard Grants” – which were typically rather small, usually funding one postdoctoral researcher and bits and bobs – and “Rolling Grants” – which were usually larger, covering all the activities of a department or institution – with a single system of “Consolidated Grants”. The Standard Grants were “responsive”, in that investigators could put in an application whenever they wanted, whereas Rolling Grants were on a fixed timetable. After the change, the responsive mode went out the window and Departments were forced to apply collectively, once every three years.

Much of the reason for the change was the administrative cost of the system. There were huge numbers of standard grant applications. Back in the mists of time there were two application deadlines per year so it was a heavy burden on the panels and the Swindon office, especially since so little funding was available in the first place. Standard grants were also the first to get squeezed when there was a funding shortfall, whereas Rolling grants generally carried on rolling.

Well, the news is that the current Astronomy grant round, with applications in 2022 and grants starting in 2023, will see the last of these Consolidated Grants. From this year on, there will be a new system of – wait for it – “Small” and “Large” grants, thought these are officially called Type 1 and Type 2. The Small Awards scheme is described here and it looks very much like the old Standard Grant system. Details of the Large grants scheme are not yet available, but I believe they will start next year. You can find more details here (PDF).

So now it seems something very like the old system is returning, and there are no doubt the same worries that Large grants will eat up most of the money, leaving very little for the Small grants. Déjà vu.

Anyway, the way I came across this piece of news was via the announcement of a clutch of PDRA positions in cosmology and extragalactic astrophysics at the University of Sussex (where I worked from 2013-16). It seems the Astronomy Centre must have done pretty well in the (final) STFC Consolidated Grant round, which is very good to hear! It seems there might be a bit more money generally in the grant line this year too, which is also good news.