Archive for Cosmology

Professorial Position in Observational Astrophysics or Cosmology at Maynooth!

Posted in Maynooth, The Universe and Stuff with tags , , , , on May 30, 2022 by telescoper

With about a month to go to the deadline, I thought I would take the opportunity to remind readers that Maynooth University has a Chair (i.e. Full Professor) position in Astrophysics or Cosmology under the Strategic Academic Leadership Initiative (SALI). I blogged about this scheme here and announced this Chair position originally here.

You can find the full announcement of the competition for all the SALI positions here; you can apply for the position at Maynooth here. The position is now also advertised on the AAS Jobs Register here.

The deadline for applications is in July 2022, and the provisional start date is January 2023 (although this is flexible). As well as a good salary (starting at €124,683 at current rates, rising by annual increments to €157,611) the position comes with membership of the Irish public service pension scheme, a defined benefit scheme (comparable to the older version of the UK’s USS which has now been scrapped).

The key rationale for these SALI positions is clear from the statement from Simon Harris, the Minister responsible for Third Level education in Ireland:

“Championing equality and diversity is one of the key goals of my department. The Senior Academic Leadership Initiative (SALI) is an important initiative aimed at advancing gender equality and the representation of women at the highest levels in our higher education institutions.

We have a particular problem with gender balance among the staff in Physics in Maynooth, especially in Theoretical Physics where all the permanent staff are male, and the lack of role models has a clear effect on our ability to encourage more female students to study with us.

The wider strategic case for this Chair revolves around broader developments in the area of astrophysics and cosmology at Maynooth. Currently there are two groups active in research in these areas, one in the Department of Experimental Physics (which is largely focussed on astronomical instrumentation) and the other, in the Department of Theoretical Physics, which is theoretical and computational. We want to promote closer collaboration between these research strands. The idea with the new position is that the holder will nucleate and lead a new research programme in the area between these existing groups as well as getting involved in outreach and public engagement.

It is intended that the position to appeal not only to people undertaking observational programmes using ground-based facilities (e.g. those provided by ESO, which Ireland recently joined), or those exploiting data from space-based experiments, as well as people working on multi-messenger astrophysics, gravitational waves, and so on.

Exciting as this position is in itself, it is part of wider developments and we are expecting to advertise further job opportunities in physics and astronomy very soon! I’d be happy to be contacted by any eligible person wishing to discuss this position (or indeed the general situation in Maynooth) on an informal basis.

Two New Publications at the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff with tags , , , , , , on May 29, 2022 by telescoper

Last week was rather busy. Amongst other things I managed to complete the publication process for two more papers in the Open Journal of Astrophysics (one on Tuesday and one on Thursday) although there was a small delay in registering the metadata so I didn’t fully announce them until yesterday. I’ve only just managed to find time today to advertise them here. These two are the sixth and seventh papers in Volume 5 (2022) and the 54th and 55th in all respectively. Both the new papers are in the folder marked Cosmology and Nongalactic Astrophysics.

The first of these two new publications is entitled “The Impact of Quadratic Biases on Cosmic Shear” and is written by Tom Kitching and Anurag Deshpande of the Mullard Space Science Laboratory in Surrey (UK).

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

You can click on the image to make it larger should you wish to do so. You can find the arXiv version of this paper directly here.

The second new publication is entitled “Cosmo-Paleontology: Statistics of Fossil Groups in a Gravity-Only Simulation” and is written by Aurora Coissairt, Michael Buehlmann, Eve Kovacs, Xin Liu, Salman Habib and Katrin Heitmann all from the Argonne National Laboratory which is just outside Chicago in the USA.

Here is the overlay of that paper which includes the abstract:

Once again You can click on the image to make it larger should you wish to do so. You can find the arXiv version of the paper here.

We have quite a few more papers in the pipeline so expect to be announcing more quite soon, probably early next month.

Euclid Launch Concern

Posted in Politics, Science Politics, The Universe and Stuff with tags , , on April 27, 2022 by telescoper

I saw the following picture on Twitter. It was taken during a talk at the annual Euclid Consortium Meeting (which I am not at) and it gives a not -very-optimistic update about the timescale for the launch of Euclid.

Picture Credit: Hervé Aussel

I thought a delay in the launch was inevitable as soon as news broke of the Russian invasion of Ukraine (see here) because the original plan was to launch on a Russian Soyuz vehicle. The subsequent decision by the Russians to remove all their personnel from the launch site at Kourou (see here) made these even more likely, although according to the slide not certain.

The basic problem is that Plan B involves launching Euclid on an Ariane 6 rocket (which comes in two varieties, Ariane62 and Ariane64, with two and four payloads boosters respectively). The problems are (a) that Ariane 6 is that it hasn’t yet had its first flight and (b) Euclid isn’t the only spacecraft having to find an alternative launcher. The competition from commercial and military satellites may mean a lengthy delay to the Euclid Launch unless lobbying succeeds at a political level, which is what the last lines of the slide are about.

Being one of life’s pessimists I think a long delay is the likeliest outcome, though this is not based on any specific knowledge at all about the discussions going on and I’d be delighted to be proved wrong. I am now however seriously wondering whether Euclid will be launched before I retire!

Distant Things!

Posted in The Universe and Stuff with tags , , , on April 1, 2022 by telescoper

I’m a bit late passing this on but there was a great deal of excitement this week at the news that the Hubble Space Telescope (HST) has made an astonishing discovery about the early Universe as illustrated by the above picture published in Nature. As well as an individual star (?) observed at redshift 6.2, so distant that its light set out when the Universe was just 8% of its current age, the image also reveals the presence in the early Universe of large geometric shapes (such as rectangles) as well as a remarkable giant arrow. The presence of these features at such high redshift is completely inconsistent with the standard theory of structure formation.

New Professorial Position in Astrophysics or Cosmology at Maynooth!

Posted in Maynooth, The Universe and Stuff with tags , , , , on March 31, 2022 by telescoper

You may recall that back in November 2021 we received word that Maynooth University had been awarded one of ten new senior professorial positions under the Strategic Academic Leadership Initiative (SALI). I blogged about this scheme here. The position we have been awarded is a Chair (Full Professorship) in Observational Astrophysics or Cosmology; you can find Maynooth University’s official response to the original announcement here.

The wheels have turned fairly slowly since the announcement but today at last the applications opened for the new Chairs, including the one in Maynooth. You can find the full announcement of the competition for all the positions here; you can apply for the position at Maynooth here. I think the advertisement will appear on a number of the standard job platforms (such as the Times Higher) too, although this is all being managed centrally. The deadline is in July 2022, and the provisional start date is January 2023 (although this is flexible).

Update: you can find an advertisement for the position on the Times Higher website here. A more complete advertisement can be found here.

The key rationale for these SALI positions is clear from the statement from Simon Harris, the Minister responsible for Third Level education in Ireland:

“Championing equality and diversity is one of the key goals of my department. The Senior Academic Leadership Initiative (SALI) is an important initiative aimed at advancing gender equality and the representation of women at the highest levels in our higher education institutions.

We have a particular problem with gender balance among the staff in Physics in Maynooth, especially in Theoretical Physics where all the permanent staff are male, and the lack of role models has a clear effect on our ability to encourage more female students to study with us.

The wider strategic case for this Chair revolves around broader developments in the area of astrophysics and cosmology at Maynooth. Currently there are two groups active in research in these areas, one in the Department of Experimental Physics (which is largely focussed on astronomical instrumentation) and the other, in the Department of Theoretical Physics, which is theoretical and computational. We want to promote closer collaboration between these research strands. The idea with the new position is that the holder will nucleate and lead a new research programme in the area between these existing groups as well as getting involved in outreach and public engagement.

It is intended that the position to appeal not only to people undertaking observational programmes using ground-based facilities (e.g. those provided by ESO, which Ireland recently joined), or those exploiting data from space-based experiments, as well as people working on multi-messenger astrophysics, gravitational waves, and so on.

Exciting as this position is in itself, it is part of wider developments and we are expecting to advertise further job opportunities in physics and astronomy very soon! I’d be happy to be contacted by any eligible person wishing to discuss this position (or indeed the general situation in Maynooth) on an informal basis.

P. S. For those of you reading this from outside Ireland the job includes a public service pension, a defined benefit scheme way better than the UK’s USS.

The art of building a smooth cosmic distance ladder in a perturbed universe

Posted in The Universe and Stuff with tags , , on February 22, 2022 by telescoper

Catching up on some literature on the inestimable arXiv I came across this paper by Obinna Umeh which I haven’t gone through in detail but which looks very interesting:

How does a smooth cosmic distance ladder emerge from observations made from a single location in a lumpy Universe? Distances to the Type Ia supernova (SN1A) in the Hubble flow are anchored on local distance measurements to sources that are very nearby. We described how this configuration could be built in a perturbed universe where lumpiness is described as small perturbations on top of a flat Friedmann-Lemaıtre Robertson-Walker (FLRW) spacetime. We show that there is a non-negligible modification (about 11%) to the background FLRW area distance due to the presence of inhomogeneities in the immediate neighbourhood of an observer. We find that the modification is sourced by the electric part of the Weyl tensor indicating a tidal deformation of the local spacetime of the observer. We show in detail how it could impact the calibration of the SN1A absolute magnitude in the Hubble flow. We show that it resolves the SN1A absolute magnitude and Hubble tensions simultaneously without the need for early or late dark energy.

The area distance here is what I usually call the angular-diameter distance; when one thinks of supernova measurements one usually thinks of the luminosity distance but these are related through the reciprocity relation discussed here which applies to each source regardless of whether the metric is of FLRW form or not. For a general discussion of cosmological distances see here.

New Publication at the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff with tags , , , on February 21, 2022 by telescoper

It’s time yet again to announce a new publication in the Open Journal of Astrophysics! This one is the 3rd paper in Volume 5 (2022) and the 51st in all. We actually published this on Friday, byt I’ve only just got around to announcing it here now.

The latest publication is entitled Differentiable Predictions for Large Scale Structure with SHAMNet and is written by Andrew Hearin, Nesar Ramachandra and Matthew R. Becker of the Argonne National Laboratory and Joseph DeRose of the Lawrence Berkeley Laboratory (both institutions being in the USA).

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

You can click on the image to make it larger should you wish to do so. You can find the arXiv version of the paper here. This paper is in our popular Cosmology and Non-galactic Astrophysics section.

P. S. Here’s a bit of feedback from the author of this paper about the referees:

They reviewed the paper in conscientious detail, and every comment was thoughtful. We feel that our paper has materially improved in clarity as a result of their critique.”

Sins of Omission

Posted in The Universe and Stuff with tags , , , , , on February 20, 2022 by telescoper

There’s a paper recently published in Nature Astronomy by Moreno et al, which you can find on the arXiv here. The title is Galaxies lacking dark matter produced by close encounters in a cosmological simulation and the abstract is here:

The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics (stellar masses, sizes, velocity dispersions and morphologies). Here we show that the standard paradigm naturally produces galaxies lacking dark matter with internal characteristics in agreement with observations. Using a state-of-the-art cosmological simulation and a meticulous galaxy-identification technique, we find that extreme close encounters with massive neighbours can be responsible for this. We predict that approximately 30 percent of massive central galaxies (with at least 1011 solar masses in stars) harbour at least one dark-matter-deficient satellite (with 108 – 109 solar masses in stars). This distinctive class of galaxies provides an additional layer in our understanding of the role of interactions in shaping galactic properties. Future observations surveying galaxies in the aforementioned regime will provide a crucial test of this scenario.

It’s quite an interesting result.

I’m reminded of this very well known paper from way back in 1998, available on arXiv here, by Priya Natarajan, Steinn Sigurdsson and Joe Silk, with the abstract:

We propose a scenario for the formation of a population of baryon-rich, dark matter-deficient dwarf galaxies at high redshift that form from the mass swept out in the Intergalactic Medium (IGM) by energetic outflows from luminous quasars. We predict the intrinsic properties of these galaxies, and examine the prospects for their observational detection in the optical, X-ray and radio wavebands. Detectable thermal Sunyaev-Zeldovich decrements (cold spots) on arc-minute scales in the cosmic microwave background radiation maps are expected during the shock-heated expanding phase from these hot bubbles. We conclude that the optimal detection strategy for these dwarfs is via narrow-band Lyman-α imaging of regions around high redshift quasars. An energetically scaled-down version of the same model is speculated upon as a possible mechanism for forming pre-galactic globular clusters.

It’s true that the detailed mechanism for forming dwarf galaxies with low dark matter densities is different in the two papers, but it does show that the issue being addressed by Moreno et al. had been addressed before. It seems to me therefore that the Natarajan et al. paper is clearly relevant background to the Moreno et al. one. I always tell junior colleagues to cite all relevant literature. I wonder why Moreno et al. decided not to do that with this paper?

Had Moreno et al. preprinted their paper before acceptance by Nature Astronomy I’m sure someone would have told them of this omission. This is yet another reason for submitting your papers to arXiv at the same time as you submit them to a journal rather than waiting for them to be published.

New Publication at the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff with tags , , , , on January 18, 2022 by telescoper

It’s a New Year and therefore a new Volume of the Open Journal of Astrophysics and it’s time to announce the first publication in it! This one is the 1st paper in Volume 5 (2022) and the 49th in all.

The latest publication is entitled Validating Synthetic Galaxy Catalogs for Dark Energy Science in the LSST Era and is written by Eve Kovacs of Argonne National Laboratory and 38 others on behalf of the LSST Dark Energy Science Collaboration.

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

You can click on the image to make it larger should you wish to do so. You can find the arXiv version of the paper here. This is another one for the Cosmology and Nongalactic Astrophysics folder, which remains the most popular category so far on the Open Journal of Astrophysics site.

There is a little bit of a backlog in OJAp Towers owing to the Christmas break as some authors have been on leave and not doing their revisions, so I’d anticipate a few more papers in the next few weeks.

Congratulations to the 2022 RAS Award Winners!

Posted in The Universe and Stuff with tags , , , , , on January 15, 2022 by telescoper

Given all the doom and gloom going around I thought I’d take the opportunity to share some good news and also offer my public congratulations to the all the winners of medals and awards announced yesterday by the Royal Astronomical Society. Let me draw particular attention to the following subset, purely on the grounds that I know them and their work personally (and because they’ve all either been mentioned on this blog recently and/or been known to read it from time to time and/or have recently published in the Open Journal of Astrophysics and/or are on the Editorial Board thereof).

First, the Gold Medal goes to Professor George Efstathiou of Cambridge University a true giant of cosmology (metaphorically speaking of course – I’m actually taller than him):

I’m looking forward to George receiving his medal so he can tell us what kind of chocolate is inside.

Second, Professor Alan Heavens of South Kensington Technical College Imperial College London who gets the Eddington Medal:

I should mention that among many other things Alan has worked extensively on the application of Bayesian methods to cosmological data.

Third, Professor Catherine Heymans of Edinburgh, Astronomer Royal for Scotland, wins the Herschel medal;

Catherine was actually a PhD student supervised by Alan Heavens back in the day. I wonder if this is the first time that a PhD student/supervisor combination has won RAS medals in the same year?

Correction: I’m now told that Catherine actually did her PhD in Oxford supervised by Lance Miller so I withdraw the question.

And last but by no means least we have Professor Pedro Gil Ferreira who will give this year’s Gerald Whitrow lecture:

Two interesting facts about Pedro: (i) a direct English translation of “Pedro Ferreira” would be “Peter Smith”; and (ii) he is a member of the Editorial Board of the Open Journal of Astrophysics.

Congratulations to them and indeed to all the winners of awards and medals, a complete list of whom may be found here.

P.S. It suddenly struck me when I saw the announcements yesterday evening that it’s now two years since I last attended the RAS Ordinary Meeting in person or the RAS Club Dinner. Let’s hope these can start again reasonably soon.