Archive for the The Universe and Stuff Category

New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , on December 1, 2023 by telescoper

It’s Friday and I thought I’d take  the opportunity before the weekend to announce yet another new paper at the Open Journal of Astrophysics.

The latest paper is the 46th so far in Volume 6 (2023) – just four to go for a half-century – and it’s the 111th altogether. This one was actually published on Wednesday November 29th.

The title is “Optimization and Quality Assessment of Baryon Pasting for Intracluster Gas using the Borg Cube Simulation” and it presents an algorithm for adding baryons to gravity-only simulations via a “pasting” approach. It is in the folder marked Cosmology and Nongalactic Astrophysics.

There are 8 authors: F. Kéruzoré;  L. Bleem; M. Buehlmann;  J.D. Emberson; N. Frontiere; S. Habib; K. Heitmann; and P. Larsen;  all of them based at the Argonne National Laboratory, in Illinois (USA).

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

Hubble Tension Reviewed

Posted in The Universe and Stuff with tags , , on November 24, 2023 by telescoper

Just a quick post to pass on a reference to a paper on arXiv (to appear in Annual Reviews of Astronomy and Astrophysics) about the ongoing saga of the Hubble Tension. The authors are Licia Verde, Nils Schöneberg, and Héctor Gil-Marín, three members of the ICCUB which is hosting me during my sabbatical. I saw an earlier draft of this paper but didn’t want to blog about it before the final version appeared. The abstract (which I’ve slightly reformatted) reads:

The Hubble parameter H0, is not a univocally-defined quantity: it relates redshifts to distances in the near Universe, but is also a key parameter of the ΛCDM standard cosmological model. As such, H0 affects several physical processes at different cosmic epochs, and multiple observables. We have counted more than a dozen H0‘s which are expected to agree if a) there are no significant systematics in the data and their interpretation and b) the adopted cosmological model is correct. With few exceptions (proverbially confirming the rule) these determinations do not agree at high statistical significance; their values cluster around two camps: the low (68 km/s/Mpc) and high (73 km/s/Mpc) camp. It appears to be a matter of anchors: the shape of the Universe expansion history agrees with the model, it is the normalizations that disagree. Beyond systematics in the data/analysis, if the model is incorrect there are only two viable ways to “fix” it: by changing the early time (z≳1100) physics and thus the early time normalization, or by a global modification, possibly touching the model’s fundamental assumptions (e.g., homogeneity, isotropy, gravity). None of these three options has the consensus of the community. The research community has been actively looking for deviations from ΛCDM for two decades; the one we might have found makes us wish we could put the genie back in the bottle.

arXiv:2311.13305


You can read the full paper here to learn about the scientific arguments, but I’d like to draw attention to this excerpt which is of more general relevance and with which I agree wholeheartedly:

It is also fair to say that the developments of the last decade have changed the expectations and modus operandi of a big part of the community. The community now expects results to be reproducible, hence the data and key software to be publicly available in such a way that a practitioner not involved in the original analysis could still retrace and reproduce all important steps and findings. While research areas such as the CMB and large-scale structure made this transition to “open science” about two decades ago, this was not the case for other areas of extra-galactic astronomy, but this is now changing.

arXiv:2311.13305

Challenging the Standard Cosmological Model

Posted in The Universe and Stuff with tags on November 20, 2023 by telescoper

I have been asked to use the medium of this blog to transmit information about a forthcoming event at the Royal Society – that’s English for Real Sociedad – next April.

This is a scientific discussion meeting organised by Prof James Binney FRS, Dr Roya Mohayaee, Prof John Peacock FRS & Prof Subir Sarkar to be held from 15-16 April 2024, 09:00-17:00, The Royal Society, London SW1Y 5AG. Here’s a description:

Is the universe simple enough to be adequately described by the standard ΛCDM cosmological model which assumes the isotropic and homogeneous Friedmann-Lemaître-Robertson-Walker metric? Tensions have emerged between the values of cosmological parameters estimated in different ways. Do these tensions signal that our model is too simple? Could a more sophisticated model account for the data without invoking a Cosmological Constant?

The meeting is free to attend – both in-person and on-line attendance available. Advance registration is essential (an optional lunch is available to purchase during registration).

Meeting papers will be published in Philosophical Transactions of the Royal Society A.

For the full Chapter and Verse see the meeting website here.

Thoughts of Retirement

Posted in Barcelona, Biographical, Maynooth, Open Access, The Universe and Stuff with tags , , , on November 19, 2023 by telescoper

I’ve been reviewing my situation while here in Barcelona. One of the themes that keeps popping into my head is well expressed by part of a little speech by Colonel Nicholson in The Bridge on the River Kwai:

But there are times… when suddenly you realize you’re nearer the end than the beginning. And you wonder, you ask yourself, what the sum total of your life represents. What difference your being there at any time made to anything – or if it made any difference at all, really. Particularly in comparison with other men’s careers. I don’t know whether that kind of thinking’s very healthy, but I must admit I’ve had some thoughts on those lines from time to time.

Healthy or not I’ve also had thoughts along those lines, and sometimes feel I should step aside and create a job opportunity for someone younger. I know my employer wouldn’t mind if I did that either. They’d much prefer replacing me with someone cheaper and more compliant than me. I think if I asked for early retirement they would probably jump at the chance. I’d miss the teaching and the students, of course,

The fact of the matter is though that I can’t afford to retire yet. I have a mortgage to pay and I’ve only had five full years of pensionable service in the Irish system, so won’t get much of a pension. I have the frozen residue of my UK pension, of course, but that is subject to an actuarial reduction if I take the benefit before I’m 65, which is also the standard retirement age for academic staff in Ireland. I can’t be made to retire here until I’m 70, in fact, but I think I’ll be well beyond my best-before date by then and am not keen to overstay my welcome.

So it looks like I’ll have to stay until I’m 65 at the earliest. In fact I won’t be able to collect the State Pension (SPC) until I’m 66, so I’ll probably have to stay another year. That means that when I get back from sabbatical I will have four or five years left until I can retire. I don’t know what I’ll be teaching when I return but I hope I get a chance to teach a few new modules before the end. In particular some cosmology or astrophysics would be particularly nice. All this is predicated on: (a) me living long enough; and (b) Physics at Maynooth not being closed down; neither of these is certain.

When I moved to the Emerald Isle in 2017 I supposed that I would carry on living in Ireland after retiring. Now I’m having some doubts about that. I have been advised by medical experts that my arthritis would be more tolerable in a warmer climate. And there’s the cost of living in Ireland, which is much higher than Spain. I can imagine living here, actually, though I think Barcelona itself might be a bit expensive for a pensioner. Somewhere in the surrounding countryside, or along the coast, might be nice. I’ve got a few years to think about that.

Another thing in my mind is what will happen to the Open Journal of Astrophysics when I retire? I would like some larger organization or community to take it over in the long term. It’s not expensive to run, actually, but someone would have to take over as Managing Editor. Moreover, I don’t think it’s really fair to expect one small University in Ireland to bear the full cost of a global astrophysics journal indefinitely.

The Little Book of Irish Research

Posted in Euclid, Maynooth, The Universe and Stuff with tags , on November 18, 2023 by telescoper

Yesterday, the last day of Science Week, saw the launch by Simon Harris TD, Minister for Further and Higher Education, Research, Innovation and Science, of the Little Book of Irish Research. This book, which is aimed at school students, so is written at an elementary level, gives quick summaries of areas of research that the general public said that they were interested in, grouped into sixteen themes, and it will be distributed to schools all round Ireland.

I was very gratified to see myself get a mention (on page 41), though it’s not really about me but about Euclid which has generated considerable interest in the general public already and is set to continue doing that for many years. As you can see, there’s also a double-page spread of JWST, though unfortunately it does not name the scientists involved; Paddy Kavanagh is the main man at Maynooth for matters JWST.

I understand The Little Book of Irish Research will be the focus of a social media campaign over coming weeks, which will hopefully make more people more aware of the research going on in all disciplines in Ireland. I think we’ll find it useful for our own outreach events, open days, etc, in the Department of Theoretical Physics, and so will the many colleagues in other Departments whose work is also featured.

I haven’t seen hard copies of the book yet, as I’m in Barcelona, but if you want to read it here is a PDF file of the whole thing for you to download at your leisure.

New Publication at the Open Journal of Astrophysics

Posted in mathematics, OJAp Papers, Open Access, The Universe and Stuff with tags , , , on November 17, 2023 by telescoper

It’s Friday afternoon but before I collapse, exhausted, into the arms of the weekend I’ll take  the opportunity to announce yet another new paper at the Open Journal of Astrophysics.

The latest paper is the 45th so far in Volume 6 (2023) – just five to go for a half-century – and it’s the 110th altogether. This one was actually published on Tuesday November 14th.

The title is “Marginalised Normal Regression: Unbiased curve fitting in the presence of x-errors” and it’s by Deaglan J. Bartlett (Institut d’Astrophysique de Paris, France) and Harry Desmond (Portsmouth, UK). It sounds like a statistical methods paper, and indeed it is, but remember that there’s a very long historical connection between astronomy and the development of statistical methods for data analysis, and this paper tackles a very longstanding issue: how best to fit curves in the presence of noisy data. This paper presents a new method for doing this, together with applications to cosmological and astrophysical data, and accompanying software. It is in the folder marked Instrumentation and Methods for Astrophysics.

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

Ireland, CERN and Science

Posted in Science Politics, The Universe and Stuff with tags , , , , , on November 15, 2023 by telescoper

And lo! it came to pass that Minister for Further and Higher Education, Research, Innovation and Science Simon Harris TD has today secured Government approval to submit Ireland’s formal application to join the European Organization for Nuclear Research (CERN) as an Associate Member.

I have posted about this before, for example here. Currently Ireland is in the anomalous position of not having any form of association agreement with CERN; the list of Full and Associate Member states can be found here.

There is an important point about CERN membership, however, which I hope is not sidelined. The case for joining CERN made at political levels is largely about the return in terms of the potential in contracts to technology companies based in Ireland from instrumentation and other infrastructure investments. This was also the case for Ireland’s membership of the European Southern Observatory, which Ireland joined about five years ago. The same thing is true for involvement in the European Space Agency, which Ireland joined in 1975. These benefits are of course real and valuable and it is entirely right that arguments should involve them.

Looking at CERN membership from a scientific point of view, however, the return to Ireland will be negligible unless there is a funding to support scientific exploitation of the facility. That would include funding for academic staff time, and for postgraduate and postdoctoral researchers to build up an active community as well as, e.g., computing facilities. This need not be expensive even relative to the modest cost of associate membership (approximately  €1.9M). I would estimate a figure of around half that would be needed to support CERN-based science.

The problem is that research funding for fundamental science (such as particle physics) in Ireland is so limited as to be virtually non-existent by a matter of policy at Science Foundation Ireland, which basically only funds applied research. Even if it were decided to target funding for CERN exploitation, unless there is extra funding that would just lead to the jam being spread even more thinly elsewhere.

As I have mentioned before, Ireland’s membership of ESO provides a cautionary tale. The Irish astronomical community was very happy about the decision to join ESO, but that decision was not accompanied by significant funding to exploit the telescopes. Few astronomers have therefore been able to benefit from ESO membership. While there are other benefits of course, the return to science has been extremely limited. The phrase “to spoil a ship for a ha’porth of tar” springs to mind.

Although Ireland joined ESA almost fifty years ago, the same issue applies there. ESA member countries pay into a mandatory science programme which includes, for example, Euclid. However, did not put any resources on the table to allow full participation in the Euclid Consortium. There is Irish involvement in other ESA projects (such as JWST) but this is somewhat piecemeal. There is no funding programme in Ireland dedicated to the scientific exploitation of ESA projects.

Under current arrangements the best bet in Ireland for funding for ESA, ESO or CERN exploitation is via the European Research Council but to get a grant from that one has to compete with much better developed communities in those areas.

A significant shake-up of research funding in Ireland is in view, with Science Foundation Ireland and the Irish Research Council set to merge into a single entity called Research Ireland. If I had any say in the new structure I would set up a pot of money specifically for the purposes I’ve described above. Funding applications would have to be competitive, of course, and I would argue for a panel with significant international representation to make the decisions. But for this to work the overall level of public sector research funding will have to increase dramatically from its current level, well below the OECD average. Ireland is currently running a huge Government surplus which is projected to continue growing until at least 2026. Only a small fraction of that surplus would be needed to build viable research communities not only in fundamental science but also across a much wider range of disciplines. Failure to invest now would be a wasted opportunity.

Astrophysics & Cosmology Masterclass at Maynooth

Posted in Maynooth, The Universe and Stuff with tags , , , on November 13, 2023 by telescoper

Both my regular readers may remember that for the last couple of years at this time of year there has been an Astrophysics & Cosmology Masterclass at Maynooth; see here and here for the previous incarnations. Not being in Maynooth I almost forgot about this year’s Masterclass, which has a different line-up with Dr Paddy Kavanagh adding some observational content alongside Dr John Regan.

This event is online only from 10am to 12pm on Friday 17th November 2023 and you can find out more details and register here.

Three New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , , , , , on November 12, 2023 by telescoper

It’s been a busy week generally, and specifically at the  Open Journal of Astrophysics. In fact, this week we have published three papers, which I didn’t have time to post here at the time we published them but now present to you. These take the count in Volume 6 (2023) up to 44 and the total published by OJAp up to 109. With many more in the pipeline we’re still on for 50 by the end of the year.

In chronological order, the three 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. All three of these papers are in the folder Cosmology and Nongalactic Astrophysics.

First one up is “On the degeneracies between baryons, massive neutrinos and f(R) gravity in Stage IV cosmic shear analyses” by Alessio Spurio Mancini (Mullard Space Sciences Laboratory, University College London, UK) and Benjamin Bose (Royal Observatory Edinburgh, UK). This presents a fast nonlinear matter power spectrum emulator for f(R) gravity with massive neutrinos, coupled with a baryon feedback emulator forecasts for a cosmic shear experiment with typical Stage IV specifications. This paper was published on 6th November 2023.

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 “” by Marika Asgari (Hull, UK), Alexander Mead (Bochum, Germany) and Catherine Heymans (Edinburgh, UK).  This presents a thorough discussion of the popular halo model for cosmological structure with applications, accompanied by the release of a software suite called pyhalomodel (which you can download here). The paper was also published on 7th November 2023 and you can see the overlay here:

 

 

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

The last paper of this batch is  entitled “Dissecting the Thermal SZ Power Spectrum by Halo Mass and Redshift in SPT-SZ Data and Simulations” and the authors are: by Josemanuel Hernandez (Chicago), Lindsey Bleem (Chicago) , Thomas Crawford (Chicago), Nicholas Huang (Berkeley), Yuuki Omori (Chicago), Srinivasan Raghunathan (NCSA, Urbana) & Christian Reichardt (Melbourne). This paper, a study of the mass and redshift dependence of the thermal Sunyaev-Zeldovich effect in South Pole Telescope data and a comparison thereof with theoretical calculations, was published on 9th November 2023.

Here is the overlay:

 

 

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

Northern Lights over Maynooth

Posted in Maynooth, The Universe and Stuff with tags , , on November 9, 2023 by telescoper
It seems the Northern Lights have been seen over Maynooth! 

(picture by @_fidel_astro on Instagram)