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Dusty Stellar Nurseries from the Dark Side of a Galaxy

Posted by carsimulator on Thursday, April 26, 2012

Left-hand panel: The red colors in this image show the galaxy M66 as it appears at the sub-mm wavelength of 850 microns, while the white background shows the galaxy as it appears in visible light. Regions of cold dust that appear as dark streaks in the white image glow brightly in the red image. Right-hand panel: The SCUBA-2 image at 850 microns seen on its own. Credit: VLT/ESO, JAC, G. Bendo. Full size image (JPG, 1.5MB)

One of the world’s most powerful cameras, SCUBA-2 is producing its first detailed images of our neighbouring galaxies, revealing previously undetected vast pockets of star formation where the next generation of stars is being created. The light from these stars is usually obscured by dust, but at the sub-millimetre wavelengths that the camera is designed for, these dust lanes actually glow brightly. The images are revealed in the week of the 25th anniversary of the James Clerk Maxwell Telescope (27 April 2012) on which SCUBA-2 is mounted.

"This exquisite image from the galaxy M66 in the constellation Leo is exactly the promising start we were hoping for," said Dr. Stephen Serjeant, the team's co-leader from The Open University. "This is a wonderfully exciting taste of things to come."

When looking up at the Milky Way, an irregular pattern of dark regions obscures the light of the stars. The dark patches are caused by clouds of dust trailing through the spiral arms and blocking out the starlight that would otherwise reveal vast pockets of star formation, or stellar nurseries. These dark lanes are not exclusive to the Milky Way, but can be found in all spiral galaxies.

SCUBA-2, led by STFC’s UK Astronomy Technology Centre in Edinburgh is the most powerful camera ever developed for observing light at sub-milimetre wavelengths, 1000 times longer than we can see with our eyes. This makes it possible to detect stellar nurseries usually obscured by dust that are so remote the light they emit left them within the first billion years after the big bang.

University of Edinburgh astrophysicist Professor James Dunlop said: "These beautiful new images from SCUBA-2 show energy conservation in action, as the same dust which absorbs the blue optical light (obscuring the stars in the optical images) can be seen to re-emit at the much longer wavelengths accessible to SCUBA-2."

This image promises to be the first of many stunning results from the James Clerk Maxwell Telescope Nearby Galaxy Legacy Survey (NGLS). The main aim of the survey is to understand how the broader environment of a galaxy affects its gas and dust content. For example, galaxies in dense clusters can lose their gas and dust through interactions with other galaxies in the cluster or simply by the head wind they feel while moving through the hot gas trapped inside the cluster. The NGLS is an international collaboration led by astronomers from Canada, the Netherlands, and the United Kingdom which is using SCUBA-2 to observe 150 galaxies in the local universe.

The NGLS team has spent much of the last five years studying molecular hydrogen emission using another instrument on the James Clerk Maxwell Telescope. "It is very exciting to now see the first results from the SCUBA-2 side of our programme starting to come in," says Professor Christine Wilson, the Principal Investigator from McMaster University in Canada. "We have a unique sample of galaxies that we are studying and having SCUBA-2 data will let us measure their gas and dust content. Gas and dust usually go hand-in-hand in galaxies, but from time to time, you find a surprise."

The James Clerk Maxwell Telescope
is situated at 14,000 feet atop Mauna Kea in Hawaii

Credit: Nik Szymanek. Full size image (JPG, 1.5MB)


Sub-millimetre Light

Sub-millimetre wavelengths are much smaller wavelengths than emitted by a typical radio station, but longer wavelengths than light waves or infrared wavelengths.

They are typically measured in microns, also called micrometres. One micron is one millionth of a metre, one 10,000th of a centimetre, or one 25,000th of an inch.

Submillimetre astronomy is most sensitive to very cold gas and dust. For example, a source with a temperature of 10 K (-263°C) emits most of its energy in a broad spectral region centred around 300 microns. Such very cold material is associated with objects in formation, that is, the mysterious earliest evolutionary stages of galaxies, stars and planets. If one wants to understand the origins of these most fundamental of astronomical structures, the submillimetre is the waveband of choice.

SCUBA-2 Key Facts

  • Size: 3m (height), 2.4m (width), 2.6m (depth)
  • Weight: 4.5 tonnes (about three times the weight of a typical car)
  • Temperature of detectors: 0.1K = -272.9°C = -459.2°F
  • Submillimetre camera with 5120 pixels (4 sub arrays x 1280 pixels) at each wavelength band
  • Provides a unique wide-field submillimetre imaging capability at 450 and 850 microns
  • Hundreds of times faster at mapping large areas of sky than predecessor SCUBA to the same signal-to-noise
  • Uses superconducting transition edge sensors as the light-sensitive elements
  • Addresses a wide-range of scientific issues including how galaxies, stars and planets form
  • Acts as a wide-field "pathfinder" for the new generation of submillimetre interferometers (e.g. SMA and ALMA)
A 2001 survey by the US-based Space Telescope Science Institute revealed that scientific results from SCUBA-2's predecessor, SCUBA had been cited almost as often as those from the Hubble Space Telescope, and much more so than those from any other ground-based facility or satellite project.

The project was funded by the Science and Technology Facilities Council (STFC), the Joint Astronomy Centre (JAC), and the Canada Foundation for Innovation (CFI).

James Clerk Maxwell Telescope

  • The James Clerk Maxwell Telescope (JCMT) is the world's largest single-dish submillimetre-wave telescope.
  • It collects faint submillimetre-wavelength signals with its 15 metre diameter dish.
  • It is situated near the summit of Mauna Kea on the Big Island of Hawaii, at an altitude of approximately 4000 metres (14000 feet) above sea level.
  • It is operated by the Joint Astronomy Centre, on behalf of the UK Science and Technology Facilities Council, the Canadian National Research Council, and the Netherlands Organisation for Scientific Research.

The JCMT webpage can be found at http://www.jach.hawaii.edu/JCMT/

McMaster University

The McMaster Physics and Astronomy webpage can be found at www.physics.mcmaster.ca

The Open University

The Open University Physical Sciences webpage can be found at www8.open.ac.uk/science/physical-science

Leiden Observatory
The Leiden Observatory webpage can be found at www.strw.leidenuniv.nl


Images can be found and downloaded here


Lucy Stone
Press Officer
STFC Rutherford Appleton Laboratory
Tel: +44 (0)1235 445627/07920870125

Please note that it is best to contact these individuals by email.

Stephanie Hills
STFC Media Manager
Desk: +44 (0)1235 445398
Email: stephanie.hills@stfc.ac.uk

Dr Holly Thomas
Joint Astronomy Centre
Desk: +1 808-969-6531
Fax: +1 808-961-6516
Email: h.thomas@jach.hawaii.edu

Science Contacts

Please note that it is best to contact these individuals by email.

Prof. Christine Wilson (NGLS PI)
Department of Physics and Astronomy,
McMaster University,
Hamilton, Ontario, L8S 4M1
Tel: 1 905 525 9140 (ext)27483
email: wilson@physics.mcmaster.ca

Dr Stephen Serjeant
Head of Astronomy,
The Open University,
Milton Keynes, MK7 6AA, UK
Tel: +44 (0)1908 652724
Mob: +44 (0)7946 605913
email: s.serjeant@open.ac.uk

Dr Antonio Chrysostomou
Associate Director, JCMT
Joint Astronomy Centre
Desk: +1 808-969-6512
Email: a.chrysostomou@jach.hawaii.edu

Further Information

University of Edinburgh's Institute for Astronomy
The Open University
McMaster University
Leiden Observatory

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