Cosmology with SCUBA-2

The UK National Astronomy Meeting (this year being held in conjunction with the German Astronomical Society) is underway this week in Manchester, UK.  The conference included a specialist session on SCUBA-2 results and it was especially pleasing to see SCUBA-2 data being presented in other sessions also,including one tied to a press release issued by the SCUBA-2 Cosmology Legacy Survey and the Royal Astronomical Society.

You can read the press release, as well as a report by the BBC – don’t forget to listen to the interview on that BBC page with Prof. James Dunlop from the University of Edinburgh, one of the leaders of the SCUBA-2 Cosmology Legacy Survey.


a new semester begins, with a ‘pointed’ result…

The pointing source HH-VLA1 (left-of-centre) at 850 µm.

This week, the new 12A semester started and this sees the first time that SCUBA-2 will be used by the general JCMT community for science outside of the JCMT Legacy Surveys. Another important milestone for us all.

The image above demonstrates the potential of a different approach to doing science with SCUBA-2. The bright source to the left-of-middle is frequently used by our telescope operators to correct for drifts in the accuracy of where the telescope is pointing in the sky. Such corrective observations are made at the beginning of the night and then several times throughout, in different parts of the sky. The image above represents just 36 separate pointing observations, obtained over several, disparate nights, and has no more than 60 seconds of integrated exposure time in the central region. Yet, some interesting structure around the bright source and beyond is clearly detected.

There will be many hundreds of pointing observations taken over the course of an observing semester, and they are all stored in the JCMT Science Archive and made freely available to the public. So the potential is there for someone to look at the archive of our pointing observations, and perhaps discover something new.

SCUBA-2 cold for Christmas

Given the excitement over the SCUBA-2 press release we didn’t mention that the instrument cooled back down according to schedule and was ready for observing on the night of the 9th of December.

Unfortunately, the weather has followed with its own cool down and Mauna Kea has been suffering to its first real winter storms of this season. Since SCUBA-2 was ready to observe we have had 4 groups at the telescope: 3 from the JCMT Legacy Survey teams and one from the University of Hawaii. At the time of writing, an observer from one of those JLS teams is valiantly trying to get some data for her team!

It remains to wish you all a Merry Christmas and a Happy New Year.

SCUBA-2 press release rolls out

This slideshow requires JavaScript.

This week saw the official SCUBA-2 press release go out. The official pages can be found here:

with further imagery at the SCUBA-2 Image Gallery (a selection of which are seen in the slideshow above).

There was also a lot of interest generated in local and national press in various places ranging from Hawaii, Canada, UK and India. And in today’s world, lost of interest generated on Twitter (including some diving sites!). Here is a selection of some sites that I came across – let us know if there are more.

SCUBA-2 warm after 8-months of continuous operation

It doesn’t seem that long ago when one of our major concerns with the SCUBA-2 project was the reliability of the fridge. In March, earlier this year, we installed a liquid Helium cold trap with the aim that it should filter out any contaminants that may have inadvertantly entered the He/He-3 gas mixture.

It’s astonishing how well this has worked. As the graph above shows, the fridge has kept its temperature all the way through the last 8 months, allowing us to control the temperature of the arrays at about 0.09 K. Furthermore, consider that the fridge was designed to only ever be cold for 6  months at a time.

So just this week, we initiated a controlled warm up of SCUBA-2 so that we can carry out some essential maintenance on the refrigeration system. We will be cooling the instrument back down in a few weeks and be ready for more observing with SCUBA-2 at the start of December.

Mauna Kea earthquake ‘felt’ by SCUBA-2

Last Wednesday on the 19th of October, just after 2pm, a 4.5 magnitude earthquake shook the Big Island. These earthquakes are not an uncommon occurrence here, with frequent tremors occurring of around a magnitude of 4 and below. However, this particular earthquake happened just to the west and about 19 km below Mauna Kea and was felt by other observatories on the summit, including UKIRT where the shear pins, which protect the telescope structure from violent shakes, had to be replaced.

JCMT escaped unscathed, but the tremor was detected in the SCUBA-2 temperature logs, as can be seen in the graph above. The units on the left-hand axis are in degrees Kelvin. The mechanical energy that entered the instrument due to the earthquake was registered as a small temperature rise in the mixing chamber of SCUBA-2’s dilution refrigerator. This change in temperature was just 20 mK, or 0.02 degrees.  There were a number of aftershocks that followed, and these were also detected by the temperature sensors in the fridge, but these are harder to spot on this graph.

First observers

The first observers from the community are finally at the telescope and observing with SCUBA-2 for the JCMT Legacy Surveys. Here in the JCMT control room you we have (left to right and front) Mark Swinbank (Durham), Isaac Roseboom (Edinburgh) and David Eden (Liverpool John Moores). At the back you can see Jeff Cox, the JCMT telescope systems specialist for the night, making sure that the telescope and instrument are operating smoothly.