Archive for BOOMERANG

SPT and the CMB

Posted in The Universe and Stuff with tags , , , , , , , , , on November 30, 2012 by telescoper

I’ve been remiss in not yet passing on news  from the South Pole Telescope, which has recently produced a number of breakthrough scientific results, including:  improved cosmological constraints from the SPT-SZ cluster survey (preprint here); a new catalogue of 224 SZ-selected cluster candidates from the first 720 square-degrees of the survey (preprint here); the first measurement of galaxy bias from the gravitational lensing of the CMB (preprint here); the first CMB-based constraint on the evolution of the ionized fraction during the epoch of reionization (preprint here); the most-significant detection of non-Gaussianity induced from the gravitational lensing of the CMB (preprint here); and the most precise measurement of the CMB damping tail and improved constraints on models of Inflation (preprint here).

Here’s the graph that drew my eye (from this paper). It shows the (angular) power spectrum of the cosmic microwave for very high (angular) frequency spherical harmonics; the resolution of SPT allows it to probe finer details of the spectrum that WMAP (also shown, at lower l).

Slide1

This is an amazing graph, especially for oldies like me who remember being so impressed by the emergence of the first “acoustic peak” at around l=200 way back in the days of Boomerang and Maxima and gobsmacked by WMAP’s revelation of the second and third. Now there are at least six acoustic peaks, although of progressively lower amplitude. The attenuation of the CMB fluctuations at high frequencies is the result of diffusion damping – similar to the way high-frequency sound waves are attenuated when they pass through a diffusive medium (e.g. a gas).  The phenomenon in this case is usually called Silk Damping, as it was first worked out back in the 1960s by Joe Damping Silk.

Anyway, there’ll be a lot more CMB news early (?) next year from Planck which will demonstrate yet again that cosmic microwave background physics has certainly come a long way from pigeon shit

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Terra Nova

Posted in Art, History, The Universe and Stuff with tags , , , , , , , on February 3, 2012 by telescoper

We’re currently enduring a spell of cold weather here in Cardiff, although I think it might be rather milder here then elsewhere in the UK. My garden thermometer showed a mere -5 C when I looked at it at 7.15 this morning. The other day we had a meeting of half-a-dozen people in one of our large teaching rooms and it was absolutely freezing. I don’t know what was wrong with the heating. Yesterday I actually did a lecture in the same room, but with 80-odd “warm bodies” (or “students” as they are sometimes known) in there, it was bearable.

The cold here of course is nothing compared with that endured by Captain Scott‘s ill-fated expedition to the South Pole, but I mention it here for a number of reasons. First, the centenary of the death of Scott and his companions is coming up next month; the tragedy unfolded in March 1912. There’s actually a very special concert coming up next week, featuring Vaughan Williams’ wonderful music written for the classic film Scott of the Antarctic (which, incidentally, you can actually watch in full on Youtube). I’m definitely going along, and will probably review the performance next week, but quite a number of my colleagues are also going, for reasons which will become obvious..

The concert is special because of the very strong connections between the Scott Expedition and the City of Cardiff. Much of the financial support needed to fund the trek to the South Pole was raised from Cardiff businessmen and Scott’s ship, the Terra Nova, actually set sail from Cardiff (in June 1910) on its journey, first to New Zealand and thence to Antarctica.

Incidentally, an article in this morning’s Western Mail relates to a historic painting of the departure of the Terra Nova which is about to be auctioned:

Cardiff Bay has certainly changed a great deal since 1910, but quite a lot is recognizable, especially the Pierhead Building, which can be seen to the right. The actual docks, the locations of which are revealed by the lines of masts of tall ships, are now mainly filled in. But there is at least one other reminder of this occasion to be found at Cardiff Bay, a large waterfront bar itself called Terra Nova

There’s also a deep connection with the South Pole, and the Antarctic generally, for many members of the Astronomy Instrumentation Group here in the School of Physics & Astronomy at Cardiff University, quite a few of whom have actually been to the South Pole in connection with various experiments, including Quad,  Boomerang and BLAST, because of the unique observing conditions there.

Post Mortem

Posted in Science Politics with tags , , , , on April 6, 2009 by telescoper

Finally the full details of the Physics panel’s deliberations during the 2008 Research Assessment Exercise have been published in the form of sub-profiles, showing the breakdown of the overall scores into various components, including the rating attached to “outputs” (i.e. papers), “environment” and “esteem”; for the jargon see the RAE guidelines for submissions.

 I’ve blogged about the RAE results before: here, there, elsewhere, et cetera and passim. Andy Lawrence (e-astronomer) has now written a blog post about the latest publications from HEFCE  (commenting on the Cardiff situation with a generosity that contrasts with the offensive attitude displayed by one of my former colleagues).  Andy has also produced a graph which makes for very interesting reading:

rae_21

I’ve used my meagre graphical skills to indicate the location of Cardiff on the figure between the thick solid lines. Note the enormous gap between the panel’s assessment of our outputs (2.22) compared to the score for esteem (2.74).

I’ve mentioned before that apparently not a single one of the papers submitted by Cardiff’s excellent Astronomy Instrumentation Group was graded as 4* (world leading). Among the papers submitted by this group were several highly cited ones relating to an important Cosmic Microwave Background experiment called BOOMERANG. The panel probably judged that Cardiff hadn’t played a sufficiently prominent role in this collaboration to merit a 4*, which seems to be a completely perverse conclusion. The experiment wouldn’t have been possible at all without the Cardiff group.

Notwithstanding my disgruntlement at the particularly and peculiarly harsh assessment of Cardiff’s physics submission, there is also an indication of a more general problem. Notice how at the top right, a large number of departments has an output score seriously lagging their other score (by about 0.4 or more).

The counterexample to this trend is Loughborough, which has a very small but clearly good research activity in physics, and which scored 2.66 on its outputs but only 1.1 on environment. They are easily identified on the graph as an extreme outlier below the general trend.

Although there is no reason to expect a perfect correlation between the different elements of the overall assessment, it looks to me like the Physics panel decided to let the output score for the strong departments saturate at a level of about 2.8 whereas other panels were much more generous.

Why did they do this?

Answers on a postcard (or, better, via the comments box), please.