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How Euclid will map the Universe

Posted in Euclid, The Universe and Stuff with tags , , on August 10, 2023 by telescoper

Time for another nice little video explainer about Euclid. This one is largely about the role of large computer simulations (particularly the Flagship simulation) in preparing for (and in future in analyzing) the Euclid survey.

The full blurb accompanying the video is appended here:

ESA’s Euclid mission will create a 3D-map of the Universe that scientists will use to measure the properties of dark energy and dark matter and uncover the nature of these mysterious components. The map will contain a vast amount of data, it will cover more than a third of the sky and its third dimension will represent time spanning 10 billion years of cosmic history.

But dealing with the huge and detailed set of novel data that Euclid observations will produce is not an easy task. To prepare for this, scientists in the Euclid Consortium have developed one of the most accurate and comprehensive computer simulations of the large-scale structure of the Universe ever produced. They named this the Euclid Flagship simulation.

Running on large banks of advanced processors, computer simulations provide a unique laboratory to model the formation and evolution of large-scale structures in the Universe, such as galaxies, galaxy clusters, and the filamentary cosmic web they form. These state-of-the-art computational techniques allow astrophysicists to trace the motion and behavior of an extremely large number of dark-matter particles over cosmological volumes under the influence of their own gravitational pull. They replicate how and where galaxies form and grow, and are used to predict their distribution across the celestial sphere.

Explore the Euclid Flagship simulation in this video and get a sneak preview of the structure of the dark Universe, as we currently model it. New insights will be brought to you by the Euclid mission in the coming years.

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ITP 2023 at Maynooth

Posted in Biographical, Education, Maynooth, The Universe and Stuff on August 9, 2023 by telescoper

I’m a bit preoccupied at the moment with marking repeat examinations but, now that I have three packs done and only one to go, I thought I’d do a quick advertisement for a little meeting that takes place in Maynooth about a month from now. This is the annual Irish Theoretical Physics (ITP) Meeting which takes place in a different location in Ireland each yea. Last year it was at DIAS in Dublin; this year it’s Maynooth’s turn.

In the pat these meetings have been given different names, including Irish Quantum Foundations (IQF) and Irish Quantum Field Theory (IQFT), as well as ITP. For this reason I usually refer to it as ITPQF+…

You can find out more about the meeting here, including instructions on how to register should you wish to do so! The detailed scientific programme will be announced in due course, though there is a rumour that I might be giving a public talk on the first evening.

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Euclid First Light Video

Posted in Euclid, The Universe and Stuff on August 1, 2023 by telescoper

Following on from yesterday’s post about the “first light” images from the European Space Agency’s Euclid mission, here is a little video highlighting the brilliant work done by the instrument teams over the last month .

P.S. You can find some Irish press coverage of the first light images here.

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“First Light” Images from Euclid

Posted in Euclid, The Universe and Stuff with tags , , , , , on July 31, 2023 by telescoper

As I promised a couple of days ago, the “first light” images from the European Space Agency’s Euclid mission have now been released. You can find all the details here, but a summary is that these are “engineering” images, rather than part of the full survey to be undertaken by Euclid, and the commissioning of the instruments is not quite finished, but the telescope is now in focus and both instruments (the visual instrument, VIS, and the Near-Infrared Spectrometer & Photometer, NISP) are working well enough to show some preliminary results.

Anyway, here are the pictures released today, first from VIS:

Euclid early commissioning test images, showing an image by the VIS instrument (visible light). The full focal plane of VIS consisting of 36 detectors is shown on the left, and one detector in higher resolution on the right. Credits: © ESA/Euclid/Euclid Consortium/NASA, CC BY-SA 3.0 IGO

The next one is from NISP:

Euclid early commissioning test images, showing an image by the NISP instrument (near-infrared light). The full focal plane of NISP consisting of 16 detectors is shown on the left, and part of one detector in higher resolution on the right. Credits: © ESA/Euclid/Euclid Consortium/NASA, CC BY-SA 3.0 IGO

This final one, also from NISP, shows it working in grism mode, which allows the light from sources to be dispersed into a spectrum, enabling us to get much more information about the sources galaxies than a straightforward image would. The resulting images look a bit strange to the untrained eye – as the light from a point is spread out into a streak – but the result is wonderfully rich in information:

Euclid early commissioning test images, showing an image by the NISP instrument (near-infrared light), in its grism slitless spectroscopy mode. The full focal plane of NISP consists of 16 detectors, here a part of one detector is shown in full resolution. Credits: © ESA/Euclid/Euclid Consortium/NASA, CC BY-SA 3.0 IGO

For more information – and some higher-resolution images – see the official Euclid press release here.

For myself, I’d just say these images are absolutely amazing given that they were taken during the commissioning phase and the instruments aren’t fully tweaked yet. Over the next few weeks, there will be a performance verification phase which will tell us how good Euclid will be at meeting its science goals. But so far it’s all looking very good indeed. I’ve only ever seen simulations of what would come out and it’s very exciting to see what the real thing looks like!

Hats off to the brilliant instrumentation experts who not only designed and built the kit but who have been working so hard on the commissioning. They’ve done so much in the month that has passed since the launch!

P.S. You can find here a nice explainer of some of the instrumental artefacts you might have spotted in the images above.

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Euclid has arrived…

Posted in Euclid, The Universe and Stuff with tags , , , on July 29, 2023 by telescoper

Here’s a little video update to accompany the news that, as of yesterday (28th July), the European Space Agency’s Euclid spacecraft has reached its orbit around L2, the second Lagrange Point of the Earth-Sun system:

More news is on the way. Commissioning of the instruments is now complete and the telescope is in focus. On Monday 31st July, ESA will release the first actual images from the Euclid telescope!

Stay tuned here.

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Four New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , on July 29, 2023 by telescoper

The rate of publication at the Open Journal of Astrophysics has now reached the point at which I think I’ll have to limit myself to weekly updates here rather than announcing every paper as it appears. We still announce individual papers on social media of course, meaning Mastodon, Facebook and the platform formerly known as Twitter…

This week we have published four papers which I now present to you here. These four take the count in Volume 6 (2023) up to 31 and the total published by OJAp up to 96. I speculated earlier this year that we might reach 100 before the end of 2023, now it looks certain we will reach the century mark as early as August! It is gratifying to see the range of papers published increasing, with all four of these in different categories.

In chronological order, the four 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.

First one up is “M-σ relations across cosmic time” by David Garofalo (1), Damian J. Christian (2), Chase Hames (1), Max North (3), Keegan Thottam (1) & Alisaie Eckelbarger (1). The author affiliations are: (1) Department of Physics, Kennesaw State University, USA; (2) Department of Physics and Astronomy, California State University, Northridge, USA; (3) Department of Information Systems, Kennesaw State University, USA. This is a discussion of the relationship between black hole mass and stellar velocity dispersion discovered in low redshift galaxies and its evolution with cosmic time. The paper was published on 25th July, is in the folder marked Astrophysics of Galaxies and can be found here.

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

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

The second paper to announce is “The fastest stars in the Galaxy” by Kareem El-Badry et al. (21 authors. This one is the fourth item in the folder marked Solar and Stellar Astrophysics and it reports the spectroscopic discovery of 6 new “runaway” stars, probably the surviving members of binary star systems in which one star exploded in a Type 1a supernova. The paper was published on 27th July 2023 and you can see the overlay here:

The accepted version of this paper can be found on the arXiv here.

The next paper is in the Earth and Planetary Astrophysics folder. It is in fact only the second paper we have published in that area. It is entitled “WHFast512: A symplectic N-body integrator for planetary systems optimized with AVX512 instructions” by Pejvak Javaheri & Hanno Rein (University of Toronto, Canada) and Daniel Tamayo (Harvey Mudd College, USA). This paper presents a fast direct N-body integrator for gravitational systems, and demonstrates it using a 40 Gyr integration of the Solar System.

Here is the overlay:

 

You can find the full text for this one on the arXiv here.

Last but by no means least, published yesterday (29th July), we have a paper that asks the question “Can Einstein (rings) surf Gravitational Waves?” by Leonardo Giani, Cullan Howlett and Tamara M. Davis of the University of Queensland, Australia. The primary classification for this one is Cosmology and Nongalactic Astrophysics and it discusses the possible effect(s) of gravitational waves on gravitational lensing observations.

 

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.

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Notes to Future Self

Posted in Biographical, The Universe and Stuff with tags , on July 28, 2023 by telescoper

Yesterday I was tidying up a bit and came across the old notebooks I used when I was a research student. As I suppose is the case with everyone else, there’s quite a lot in them that never went anywhere. If you can read the example above, about 3/4 of the way down the right-hand page I left a note saying “This is a pointless task”. I can’t remember if that referred to that particular integral or my research in general!

Some people who have seen this picture remarked on the size of my integral signs. That’s because I had to do quite a lot of integrals with complicated integrands, so I got into the habit of drawing big integral signs as a prelude to writing down what I assumed would be a horrible formula.

The way I worked in those days (1985-88) was to do a lot of rough scribblings on scrap paper. When I got to something I thought was promising I would write up a “neat” version in the notebook and throw away the workings. I know younger folks these days do most of their work on a screen but, as an old fogey, I still write a lot down on paper or on a blackboard. I didn’t have my own blackboard when I was a PhD student, but I did have plenty of notebooks – most of which I have kept. I think that I’ll always find an essential part of the mathematical thought process involves a pen or piece of chalk in my hand, moving around and guiding my brain.

Looking through these books I remember that I also wrote down ideas for follow-up projects. I managed to do very few of these, but some were done by other people elsewhere independently of me, so at least they were reasonable ideas!

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The First Room-Temperature Superconductor?

Posted in The Universe and Stuff with tags , , , on July 25, 2023 by telescoper

This is outside my usual areas, but there’s a new paper on arXiv which, if verified, could be extremely important. It’s called The First Room-Temperature Ambient-Pressure Superconductor and it is written by three scientists based in Korea. High temperature superconductivity has been, er, a hot topic for some years. One must be cautious because (as far as I am aware) the article has not yet been refereed, but is this a breakthrough?

Here is the abstract:

It seems to me that 400K is a bit hot for a room, but the point is that the material behaves as a superconductor (i.e. zero resistivity) for T < Tc so cooler rooms would do! The current definition of “high temperature” is Tc > 77K which is much lower than the Tc = 400 K stated here.

Here’s part of a figure from the paper showing (right) the material LK-99 and its structure (left):

I’m not an expert, but it looks like the material involved is neither particularly expensive nor particularly complicated so it should be relatively easy to determine whether these results are reproducible.

Comments from experts are welcome!

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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 July 22, 2023 by telescoper

Time to announce yet another new paper at the Open Journal of Astrophysics. This one was published yesterday, on 21st July 2023.

The latest paper is the 27th  so far in Volume 6 (2023) and the 92nd in all. The authors are Sohan Ghodla, Richard Easther, M.M. Briel and J.J. Eldridge, all of the University of Auckland in New Zealand.

The primary classification for this paper is Cosmology and Nongalactic Astrophysics and its title is “Observational implications of cosmologically coupled black holes”.  The paper elucidates some of the consequences of a suggestion that the interaction between black holes and the global properties of space-time underlying explanation for dark energy. The key result is that the existence of cosmologically-coupled black holes implies a much larger rate of black-hole merger events than is observed.

The papers to which this is a response are mentioned here. For reference ,these earlier works were published in The Astrophysical Journal and The Astrophysical Journal Letters. There is also a detailed twitter thread about this paper by Richard Easter, posted when it was submitted as a preprint to the arXiv last month:

 

Anyway, here is a screen grab of the overlay of the published version 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.

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Four New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , on July 19, 2023 by telescoper

Time for an update at the Open Journal of Astrophysics. Owing to a well-deserved holiday by a member of the OJAp team, we were unable to register DOIs and associated metadata for a couple of weeks so refrained from announcing new papers during this period while other functions of the journal continued. Anyway, this week we have caught up with the backlog of four papers, which I now present to you here, all published on 17th July 2023. These four take the count in Volume 6 (2023) up to 26 and the total published by OJAp up to 91.

In no particular order, the four 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.

“Large-scale power loss in ground-based CMB mapmaking” by Sigurd Naess (Oslo, Norway) and Thibaut Louis (Saclay, France). This one is a discussion of the possible biases introduced by using a data model to create sky maps of CMB temperature fluctuations and is in the folder marked Instrumentation and Methods for Astrophysics.

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

 

 

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

The primary classification for the next paper paper is Cosmology and Nongalactic Astrophysics and its title is “”The cumulant generating function as a novel observable to cumulate weak lensing information”. The authors are Aoife Boyle (Saclay, France), Alexandre Barthelemy (LMU, Germany), Sandrine Codis (Saclay, France), Cora Uhlemann (Newcastle, UK) & Oliver Friedrich (LMU, Germany). The paper explores the use of the cumulant generating function (CGF), from which the probability density function (PDF) can be obtained, in the context of weak gravitational lensing information.

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.

Also in the folder marked Cosmology and Nongalactic Astrophysics is the third paper “Cosmology with 6 parameters in the Stage-IV era: efficient marginalisation over nuisance parameters” by B. Hadzhiyska (Berkeley, USA), K. Wolz (Trieste, Italy), S. Azzoni (Oxford, UK; Tokyo, Japan), D. Alonso (Oxford, UK), C. García-García (Oxford, UK), J. Ruiz-Zapatero (Oxford, UK) and A. Slosar (Tokyo, Japan). This presents an efficient analytical method to speed up marginalization over nuisance parameters introduced to model systematic effects in large-scale structure data.

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

 

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

The final paper in this quartet, also in Cosmology and Nongalactic Astrophysics, is “Modeling the Galaxy Distribution in Clusters using Halo Cores” by D. Korytov, E. Rangel, L. Bleem, N. Frontiere, S. Habib, K. Heitmann, J. Hollowed, and A. Pope (all of the Argonne National Laboratory, USA). This presents a new method to speed up numerical simulations using a method of simplifying the handling of substructure in galaxy clusters using halo ‘core-tracking’.

The overlay of this one is here:

 

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

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