Farewell to Spitzer

Just a quick post to advertise the fact that NASA’s Spitzer Space Telescope, which was launched in 2003, is due to be `retired’ at the end of January 2020. Spitzer is an infrared telescope that has done a great number of wonderful things over the past 16 years or so. Here’s a short video giving an overview of the mission.

There will be a live-streamed event next week, on January 22nd 2020, featuring mission members and NASA leadership, at 10am PST (6pm GMT/Irish Time) during which members of the public can ask questions. For more details of this event see here.

Although it’s sad to see the end of one `Great Observatory’, hopefully it would be long before the launch of the James Webb Space Telescope which should be even greater. It certainly has a much bigger budget anyway! JWST is due to be launched in March 2021.

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My Life in Physical Cosmology – Jim Peebles

This is very nice, a talk by Nobel Laureate Jim Peebles given at the Oska Klein Centre in Stockholm. Well worth watching if you want to learn about the evolution of the field of physical cosmology over the last 50 years or so.

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Luminosity Evolution in Type 1a Supernovae?

Figure 1 of Kang et al.

During this afternoon’s very exciting Meeting of the Faculty of Science and Engineering at Maynooth University I suddenly remembered a paper I became aware of over Christmas but then forgot about. There’s an article here describing the paper that makes some pretty strong claims, which was what alerted me to it. The actual paper, by Kang et al., which has apparently been refereed and accepted for publication by the Astrophysical Journal, can be found on the arXiv here. The abstract reads:

The most direct and strongest evidence for the presence of dark energy is provided by the measurement of galaxy distances using type Ia supernovae (SNe Ia). This result is based on the assumption that the corrected brightness of SN Ia through the empirical standardization would not evolve with look-back time. Recent studies have shown, however, that the standardized brightness of SN Ia is correlated with host morphology, host mass, and local star formation rate, suggesting a possible correlation with stellar population property. In order to understand the origin of these correlations, we have continued our spectroscopic observations to cover most of the reported nearby early-type host galaxies. From high-quality (signal-to-noise ratio ~175) spectra, we obtained the most direct and reliable estimates of population age and metallicity for these host galaxies. We find a significant correlation between SN luminosity (after the standardization) and stellar population age at a 99.5% confidence level. As such, this is the most direct and stringent test ever made for the luminosity evolution of SN Ia. Based on this result, we further show that the previously reported correlations with host morphology, host mass, and local star formation rate are most likely originated from the difference in population age. This indicates that the light-curve fitters used by the SNe Ia community are not quite capable of correcting for the population age effect, which would inevitably cause a serious systematic bias with look-back time. Notably, taken at face values, a significant fraction of the Hubble residual used in the discovery of the dark energy appears to be affected by the luminosity evolution. We argue, therefore, that this systematic bias must be considered in detail in SN cosmology before proceeding to the details of the dark energy.

Of course evidence for significant luminosity evolution of Type Ia supernovae would throw a big spanner in the works involved in using these objects to probe cosmology (specifically dark energy), but having skimmed the paper I’m a bit skeptical about the results, largely because they seem to use only a very small number of supernovae to reach their conclusions and I’m not convinced about selection effects. I have an open mind, though, so I’d be very interested to hear through the comments box the views of any experts in this field.

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Another Cosmologist for Maynooth!

A few people have contacted me to ask what happened with the research position in cosmology at Maynooth University advertised a few months ago. Well, I am now in a position to provide the answer.

I’m very happy to announce that as of January 2nd 2020, Dr John Regan has joined the staff of the Department of Theoretical Physics, bringing with him an SFI – Royal Society University Research Fellowship (URF) which will fund his research for five years.

Dr John Regan

John’s primary area of research is in trying to understand the formation of black holes in the early Universe and their subsequent growth and evolution. He is interested in trying to determine how the first massive black holes in the Universe formed and the conditions required to form them. The problem is well posed since at early times the Universe was a comparatively simple place compared to the Universe today. Recent observations have indicated that Supermassive Black Holes existed less than 1 billion years after the big bang (the Universe is approximately 14 billion years old). A current open problem in Cosmology is how did black holes form and grow quickly enough in order to become super-massive so early in the Universe?

In answering this question John uses high resolution numerical simulations to study the environments in which the first massive black hole seeds may have formed and then grown to become the super-massive ones we can still observe today.

I’m delighted that John has joined the Department and look forward to many years of fruitful collaborations and discussions. He will be joined by a PDRA and a research student in due course.

You can follow John on Twitter here:

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200 Years of the RAS Club

Here I am in Heathrow Terminal 2 waiting for flight back to Dublin. I managed to get to London from Birmingham in time for a special dinner to mark the 200th anniversary of the RAS Club. As I have mentioned in previous posts, according to the brief history published on the RAS website:

The ‘Astronomical Society of London’ was conceived on 12 January 1820 when 14 gentlemen sat down to dinner at the Freemason’s Tavern, in Lincoln’s Inn Fields, London. After an unusually short gestation the new Society was born on 10 March 1820 with the first meeting of the Council and the Society as a whole. An early setback, when Sir Joseph Banks induced the Duke of Somerset to withdraw his agreement to be the first President, was overcome when Sir William Herschel agreed to be the titular first President, though he never actually took the Chair at a meeting.

Since the RAS Club always dines on the second Friday of the month after Ordinary Meetings of the Royal Astronomical Society itself, January 10th was the closest date to that first dinner. As expected for such a special occasion, there was a very big turnout with more than double the usual number of diners (and many more guests than usual). It was very nice to see some people I haven’t seen for ages! The food and wine were excellent and we ended with champagne and a slice of a cake baked and decorated for the occasion. Unfortunately it was so crowded in the Gallery Room that I couldn’t get close enough to take a photo of it before it was whisked away to be cut into slices.

After dinner we had some speeches, including one really brilliant one by my former colleague from Cardiff days, Mike Edmunds who had researched the `14 gentlemen’ who attended that first dinner. I had known previously that Charles Babbage and John Herschel were there but here (thanks to Mike) is a complete list:

Charles Babbage, Esq. M.A. F.R.S. L. & E.	No. 5 Devonshire Street Portland Place
Arthur Baily, Esq,	Gray’s Inn
Francis Baily, Esq. F.R.S. & L.S.	Gray’s Inn
Major Thomas Colby, of the Royal Engineers, LL.D. F.R.S. L. & E.	Tower
Henry T. Colebrooke, Esq. F.R.S. & L.S.	Albany, Piccadilly
Olinthus G. Gregory, LL.D. Professor of Mathematics	Royal Military Academy, Woolwich
Stephen Groombridge, Esq. F.R.S. S.R.A.Nap.	Blackheath
J.F.W. Herschel, LL.D. F.R.S.	Slough
Patrick Kelly, LL.D.	Finsbury Square
Daniel Moore, Esq. F.R.S. S.A. & L.S.	Lincoln’s Inn
Rev. William Pearson, LL.D. F.R.S.	East Sheen, Surrey
James South, Esq. F.R.S. and L.S.	No. 11 Blackman Street Southwark
Charles Stokes, Esq. F.R.S. S.A. & L.S.	Gray’s Inn
Peter Slawinski D.P. Proff. University	Wilna

P.S. Because I was attending the LGBTQ+ STEMinar I couldn’t get to the ordinary meeting of the Royal Astronomical Society earlier in the day, which was a shame because it was there that the winners of this year’s awards were announced. You can find a full list here. Congratulations to all!

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LGBTQ+ STEMinar 2020

Well I made it to Birmingham (after getting up at 3.30am!) and to the Leonard Deacon Lecture Theatre in the School of Medicine at the University thereof for this year’s LGBT+ STEMinar (the 5th of a series that started in 2016).

This is the largest one of these do far, with around 250 participants, and an impressive array of sponsors:

One of the great things about the LGBTSTEMeminar (apart from the feeling of being amongst ‘family’) is the opportunity to hear talks about fields other than your own, which I am enjoying very much.

Ooh. I forgot to mention that next year’s event will also be in the Midlands, at Oxford University.

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New Publication at the Open Journal of Astrophysics!

It’s two in two days because we have published another new paper at The Open Journal of Astrophysics. The title is A Beginner’s Guide to working with Astronomical Data. Here is a grab of the overlay:

You can find the arXiv version of the paper here.

The author is Markus Pössel of the Haus der Astronomie at the Max Planck Institute for Astronomy in Heidelberg (Germany). This is a long paper – 71 pages with over a hundred figures – that gives a comprehensive introduction to the various kinds of astronomical data and techniques for working with such data. I think this paper will attract a lot of interest from many different kinds of people but it will be particularly interesting to students doing undergraduate projects involving astronomical data (and their supervisors).

Another point worth noting is that there’s a small addition to the overlay for this paper, which will apply to all future papers (and retrospectively once we have worked through the back catalogue) and that is in the bottom left of the image above. It shows that the article is published with the latest form of Creative Commons License (CC-BY-4.0). It has always been our policy to publish under a CC-BY licence but Scholastica have very helpfully set up a new facility to make this explicit on each page. This is part of our efforts to ensure that we are compliant with Plan S which makes CC-BY licenses mandatory.

UPDATE: the CC-BY-4.0 license has now been applied retrospectively to all our publications.

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