SCUBA-2 project passes two huge milestones

Close up detail of dust emission from the inner part of our Galaxy.

This is just a short note to announce that the SCUBA-2 project past two huge milestones this day. First, the instrument was formally accepted by the observatory, and, SCUBA-2 was included in the JCMT Call for Proposals for semester 12A, which will run between February and July, 2012.

The details for the call for proposals can be found here.

SCUBA-2 to be released to the community

The high mass star forming region, DR21, as imaged by SCUBA-2 at 450µm

The following announcement was recently made by Prof. Gary Davis, Director of the Joint Astronomy Centre, to the JCMT community. It marks an incredibly important milestone in the project.

To the JCMT observing community,
It is with great pleasure that I write to announce the imminent
release of SCUBA-2 for science observing!

We are now in the final stages of commissioning the instrument on the
JCMT, and I anticipate formally accepting ownership from the UKATC by
the end of this month. Accordingly, the instrument will be available
for science starting on 1st October.

The JCMT Board have determined that the JCMT Legacy Survey (JLS) is
the highest priority for the scientific use of SCUBA-2 and for the
exploitation of its unprecedented capabilities. Consequently, the
usage of SCUBA-2 during the first four months will focus exclusively
on this programme. The coordinators of the JLS projects are already
well aware of this and arrangements for the Science Verification phase
(the precursor to JLS observing) are coming together nicely.

With our initial focus on getting the JLS programme up and running, PI
access to SCUBA-2 will commence in semester 12A. We have recently
issued two announcements to this list, alerting potential PIs to the
timetable. As a reminder, the Call for 12A Proposals will be issued
on 30th September and the proposal deadline will be just two weeks
later, on 14th October. I am grateful to the national TAGs and the
ITAC for agreeing to an accelerated timetable for the time allocation
process on this occasion.

This Call will contain explicit instructions for calculating the
observing time required to reach a given depth over a given map area,
and as such the Call will represent our first public statement of the
sensitivity of the instrument.
I am of course well aware that the community has been awaiting the
release of SCUBA-2 for several years. It has been a long and winding
road to reach this point, and I thank you for your patience. I have
every expectation that it will prove to be a success!

Best regards,

Gary Davis,

Director JCMT.

SCUBA-2 to be included in call for proposals for semester 12A

An announcement via email to the JCMT community two weeks ago, indicated the approach of a hugely important milestone in the SCUBA-2 project. This announcement informed that the JCMT call for proposals for the next semester (12A, to start in February 2012) has been delayed to the end of September. With SCUBA-2 commissioning continuing apace, this delay will allow us to obtain reliable estimates of the instrument sensitivity and performance and to accommodate its inclusion in a call for proposals – for the first time, SCUBA-2 will be offered to the community in a standard call for proposals.

We are looking forward to reading all the exciting science cases for SCUBA-2.

Moving closer towards release

The W51 massive star forming complex lies just half a degree below the Galactic Plane. This quick reduction from an 850µm square degree map of the region shows a chain of cold, dense cores reaching out from the massive core and running parallel to the Plane. The contours represent 12CO emission from the region.

Despite the hiatus in activity on this blog over the last few weeks, the SCUBA-2 commissioning team have been very busy. In particular, preparation for an Instrument Performance Review, which took place at NIST in Boulder, CO, took up most of our time at the end of July. This was an important meeting where a panel of submillimetre instrumentation experts came together to review the current performance of SCUBA-2 and came up with a list of recommendations going forward. Importantly, one of the outcomes of the review is that no invasive measures could be identified that would significantly improve the performance of the instrument. This is a positive outcome and indicates that we are very close to releasing the instrument to the JCMT community.

With that in mind, and taking the recommendations of the review on board, a plan is being drawn up which takes us as quickly as possible to a release of the instrument for shared-risks observing – which we hope will be in the next couple of months. It will be for the JCMT Board to decide what form that shared-risk observing will be. We hope to hear an official announcement to the community soon.

An update on SCUBA-2 commissioning

We’re well aware that it has been over a month since the last blog post, so it’s high time to post an update on SCUBA-2 commissioning. We had been investigating the mapping capabilities of the instrument in parallel with other instrument work, but now the emphasis and focus has shifted somewhat away from mapping and towards attaining an understanding of the sensitivity of the instrument. The arrays have been optimised for on-sky operations and we are shaking down the system to gauge the instrument’s point-source sensitivity.

Some of the activities that we have been working on since the last update include:

  • finalisation of array optimisation:
    • the best bias points for the heater and the superconducting arrays have been established
  • frame rate increase:
    • we investigated increasing the rate at which each data frame is read out, with a view to reducing the amount of noise aliased from higher frequencies; this gave us an improvement of about 20% in sensitivity at 850µm and 10% at 450µm (the latter, not as high as we had hoped or anticipated)
  • noise/NEP:
    • initial calculations seemed to imply that the dark NEPs were wildly varying and of course this caused a lot of concern. A lot of effort was invested in tracking this problem down and a couple of software bug fixes later, the calculated NEPs were seen to be actually stable over time (and always had been). This is clearly important as it allows us to establish by how much we are background limited
  • weather:
    • well, there’s not much we can do about the weather but it has hampered our on sky activities. The weather the last couple of months has been very poor, with even a snow storm in June which shut down the Mauna Kea summit for a weekend. We are now beginning to see changes in the forecast which we hope will bring better weather along, and more consistently so.
  • finding and fixing software bugs
    • and of course, we continue to exercise the software, finding and fixing bugs along the way.

We are now entering a crucial phase of the project, as we move towards determining the on-sky performance of SCUBA-2.

abell 1835, a lensing cluster

The subject of this post is Abell 1835, a galaxy cluster at a redshift of z=0.25 that is so massive that it acts as a gravitational lens to amplify the emission from objects at higher (i.e. more distant) redshifts along the line of sight. As well as amplifying the emission from faint and distant galaxies, another advantage of gravitational lenses is that they amplify light achromatically, that is, the amplification is equal at all wavelengths. Gravitational lensing allows us to study the properties of distant galaxies in far greater detail than would otherwise be possible; these rare lensing systems have thus allowed astronomers to push the boundaries of our exploration of the galaxy populations of the early Universe. This was used to good effect at the start of the century with SCUBA and led to the discovery a previously hidden population of submm galaxies by surveying for bright submillimetre radiation associated with known gravitational lenses.

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Revisiting SHADES

In mid-April, we obtained some data towards the Lockman Hole, a region of the sky located in the constellation Ursa Major whose line-of-sight is devoid of interstellar hydrogen. Consequently, this provides a clear window to the rest of the Universe beyond our Milky Way and the Lockman Hole has become a popular field to observe by cosmologists.

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