Archive for Cosmic Microwave Background

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New Results from the Atacama Cosmology Telescope

Posted in The Universe and Stuff with tags , , , , , , on April 12, 2023 by telescoper

I wish to draw your attention to a clutch of new papers out on the arXiv today (here, here and here) which describe latest results from the Atacama Cosmology Telescope (ACT for short). There was a webinar about this yesterday, which I failed to attend because I forgot about it.

The first of the papers listed above summarizes the key science results, which include a mass map obtained from gravitational lensing of the cosmic microwave background and its implications for cosmology.

As cosmic background photons propagate freely through space, i.e. without scattering, from the time of recombination to the observer, they are deflected by the gravitational effect of the large-scale distribution of matter in the Universe. This lensing effect leaves imprints in the temperature and polarization anisotropies, which can be used to reconstruct a map of the lensing potential, the gradient of which determines the lensing deflections. Structures in the CMB temperature pattern look bigger on the sky if we view them through an overdense clump of dark matter. By looking how the typical size of hot and cold spots in the CMB temperature map vary across the sky, it is possible to reconstruct the lensing deflections and hence the distribution of dark matter integrated along the line of sight. Since the structure through which the radiation passes is changing with time, this sort of map can provide constraints on models for the evolution of structure.

To cut a long story short, here is the map obtained using Data Release 6 of the ACT data over about 25% of the sky:

There’s a lot of information in the three papers but the key conclusion can be found in the last sentence of the abstract of the first paper:

Our results provide independent confirmation that the universe is spatially flat, conforms with general relativity, and is described remarkably well by the ΛCDM model, while paving a promising path for neutrino physics with gravitational lensing from upcoming ground-based CMB surveys.

Nothing revolutionary, then, but interesting nevertheless. There is an article on the BBC website about these results.

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Two New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , , , , on March 26, 2023 by telescoper

I just realized that I forgot to advertise on here a couple of recent publications at the Open Journal of Astrophysics – the papers are coming in at quite a rate now – so I’ll catch up with them both in one post.

The first paper of the two is the 10th paper in Volume 6 (2023) and the 75th in all; it was published on 16th March 2023. This one is  in the folder marked Instrumentation and Methods for Astrophysics. The title is “From BeyondPlanck to Cosmoglobe: Open Science, Reproducibility, and Data Longevity” and it is a discussion of the importance of reproducibility and Open Science in CMB science including measures toward facilitating easy code and data distribution, community-based code documentation, user-friendly compilation procedures, etc.  You can find out more about the BeyondPlanck collaboration here and about Cosmoglobe here.

The first author is S. Gerakakis and there are 42 authors in all. This is too many to list individually here but they come from Greece, Norway, Finland, Germany, Italy, and the USA.

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.

The second paper is the 11th paper in Volume 6 (2023) as well as the 76th in all; this one was published last Thursday (23rd March). This is another for the folder marked Cosmology and Nongalactic Astrophysics. The title is “GLASS: Generator for Large Scale Structure” and the paper is about a new code for the simulation of cosmological observables obtainable from galaxy surveys in a realistic yet computationally inexpensive manner. The code can be downloaded here. This is an interesting approach that contrasts with the “brute force” of full numerical simulations like those I discussed a few days ago.

The authors are Nicolas Tessore (University College London), Arthur Loureiro (UCL, Edinburgh and Imperial College), Benjamin Joachimi (UCL), Maximilian von Wiestersheim-Kramsta (UCL) and Niall Jeffrey (UCL).

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.

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Latest Results from the South Pole Telescope

Posted in The Universe and Stuff with tags , , , , on December 13, 2022 by telescoper

Just time for a quick post to point out the latest results from the South Pole Telescope (SPT) have now hit the arXiv. The measurements were made in 2018 but the outcome of a full analysis of temperature and polarization has only just appeared.

Here’s a grab of the abstract:

The key figures showing the constraints on the Hubble Constant H0 and the parameter S8 are shown here:

As you can see, the results from SPT-3G are consistent with the standard cosmological model and agree on H0 with Planck rather than the higher value obtained from local measurements. If you thought there was Hubble tension before this measurement, then you will still think so now!

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Save the Holmdel Antenna!

Posted in History, The Universe and Stuff with tags , , , , on December 11, 2022 by telescoper

I’ve used the above image hundreds of times in popular talks. It shows Robert W. Wilson (left) and Arno A. Penzias (right) standing in front of the famous horn antenna that (accidentally) discovered what we now know to be the cosmic microwave background radiation left over after the Big Bang. Penzias and Wilson made their historic measurements in 1964, published their results in 1965, and received the Nobel Prize for Physics in 1978.

At the time of their historic experiment, the scientists were working at Bell Telephone Laboratories at Holmdel, New Jersey, on Project Echo. The antenna was built to receive radio signals bounced off a passive satellite in a low Earth orbit to check the feasibility of satellite radio communication. They found excess noise in their receiver, which was eventually identified as a relic of a time when the Universe was extremely hot. Coincidentally, the theory of this yet undiscovered radiation was being worked on by Bob Dicke and his group in Princeton at about the same time (and also in New Jersey). Discussions ensued, and the discovery paper by Penzias & Wilson appeared in the Astrophysical Journal in 1965 beside a paper by Dicke et al. giving the theoretical interpretation.

Anyway, in case you were wondering whatever happened to the Holmdel Antenna, it is still there in Holmdel (at the top of Crawford Hill) and in 1988 was declared a National Historic Landmark:

Bell Labs (as it was usually known) was acquired by Nokia in 2016 and subsequently called Nokia Bell Labs. In 2019, however, Nokia put the entire Holmdel site up for sale and redevelopment of the entire site is currently being considered. This would not only bring to an end the connection between Holmdel and the telecommunications industry but also places a big question mark over the famous antenna. A petition has been raised to secure the future of this extremely important piece of scientific history. I encourage you to read more about the situation here and consider signing the petition.

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Simons Observatory News

Posted in Cardiff, Science Politics, The Universe and Stuff with tags , , , on October 18, 2022 by telescoper

It seems a lot longer than four years ago that I drew the attention of readers of this blog to the science case for the Simons Observatory, the next big thing in ground-based studies of the cosmic microwave background.

The Simons Observatory Site in Chile, as it appeared four years ago

Obviously a couple of years of pandemic have intervened, amongst other things, but I was delighted to read yesterday that the UK has invested £18M in the Simons Observatory, which will enable further development of the facility at Cerro Toco, high above the Atacama Desert in Chile.

Simons Observatory in May 2022

The project was already a large international collaboration led from the USA, but the new funds from UKRI mean that six UK institutions will now join. These are (in alphabetical order): Cambridge; Cardiff; Imperial College London; Manchester; Oxford; and Sussex. Although I’m not involved in this project myself I know many people at these institutions (two of which I have worked at) and elsewhere who will be absolutely thrilled to be able to participate in this exciting project. Congratulations to them!

It would have been great if Ireland had been able to get involved in the Simons Observatory, but sadly fundamental science of this type is not a priority for the powers that be in Irish science funding. This is unfortunate because I think membership of international consortia like this would enable a small country to punch above its weight in science. Still, at least the UK PI, Prof. Michael Brown (Manchester), is an Irishman…

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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 December 6, 2021 by telescoper

Time to announce yet another publication in the Open Journal of Astrophysics. This one is the 15th paper in Volume 4 (2021) and the 46th in all.

The latest publication is entitled  Interplanetary Dust as a Foreground for the LiteBIRD CMB Satellite Mission by Ken Ganga (Paris), Michele Maris (Trieste) and Mathieu Remazeilles (Santander) on behalf of the LiteBIRD collaboration. For information about the LiteBIRD mission see here.

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

You can find the paper on the Open Journal of Astrophysics site here and can also read it directly on the arXiv here.

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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 September 23, 2021 by telescoper

Time to announce another publication in the Open Journal of Astrophysics. This one is the tenth paper in Volume 4 (2021) and the 41st in all. We actually published this one a couple of days ago but I’ve been so busy with start-of-term shenanigans that I didn’t get time to announce it until this morning.

The latest publication is entitled Consequences of constant elevation scans for instrumental systematics in Cosmic Microwave Background Experiments. The authors are Daniel B. Thomas & Nialh McCallum of Queen Mary, University of London, and Michael Brown of the University of Manchester.

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 one is also in the folder marked Instrumentation and Methods for Astrophysics, though it is obviously of relevance to Cosmology and Non-Galactic Astrophysics too.

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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 August 19, 2021 by telescoper

Time to announce another publication in the Open Journal of Astrophysics. This one is the eighth paper in Volume 4 (2021) and the 39th in all.

The latest publication is entitled A Detailed Description of the CAMSPEC Likelihood Pipeline and a Reanalysis of the Planck High Frequency Maps. The authors are George Efstathiou and Steven Gratton of the Kavli Institute for Cosmology at the University of Cambridge.

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 one is also in the folder marked Cosmology and Nongalactic Astrophysics.

This is a long and detailed paper, running to 92 pages in PDF form. Our Editorial process relies on referees being willing to volunteer their time to read and comment on submissions and this one in particular required a great deal of effort. I am always grateful to referees but in this case I am even more grateful than usual the diligence displayed during and the many useful comments received. I know who our reviewers are and they know who they are, but shall remain anonymous!

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Searching for the Predicted Peaks in the CMB Power Spectrum

Posted in The Universe and Stuff with tags , , on July 11, 2021 by telescoper

I came across this on social media and thought I’d share it here. It’s a nice graphical demonstration of the interplay between theory and experiment in the field of cosmic microwave background physics. The video was created by Forrest Fankhauser and Lloyd Knox at the University of California, Davis with funding from the National Science Foundation.

As someone famous once said: “we’ve come a long way from pigeon shit…”

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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 7, 2021 by telescoper

Time to announce another publication in the Open Journal of Astrophysics. This one was actually published last Friday, but I didn’t get time to post about it until just now. It is the fifth paper in Volume 4 (2021) and the 36th paper in all.

The latest publication is entitled Gravitational Wave Direct Detection does not Constrain the Tensor Spectral Index at CMB Scales and the author is Will Kinney of the State University of New York at Buffalo (which is SUNY Buffalo, for short).

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 one is, fairly obviously, in the Cosmology and Nongalactic Astrophysics folder..

Over the last few months I have noticed that it has taken a bit longer to get referee reports on papers and also for authors to complete their revisions. I think that’s probably a consequence of the pandemic and people being generally overworked. We do have a number of papers at various stages of the pipeline, so although we’re a bit behind where we were last year in terms of papers published I think may well catch up in the next month or two.

I’ll end with a reminder to prospective authors that the OJA  now has the facility to include supplementary files (e.g. code or data sets) along with the papers we publish. If any existing authors (i.e. of papers we have already published) would like us to add supplementary files retrospectively then please contact us with a request!

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