Game-changer for astronomical instrumentation

The team of astronomers that built the Sydney-AAO Multi-object Integral Field Spectrograph (SAMI) has been awarded the inaugural Peter McGregor prize – for their development that enables a complete picture for thousands of galaxies. 

Central to SAMI is the hexabundle, an optical element that contains many individual optical fibres precisely aligned and fused so that light can be collected from many locations across the face of a galaxy at once. The light entering the optical fibres is then fed to a spectrograph that can used to measure a huge range of physical properties such as the motion and chemistry of the gas and stars within galaxies.

Project leader Professor Scott Croom said: “Targeting galaxies with normal single optical fibres is like studying a city by just looking at the CBD. With SAMI we see the whole city, including the suburbs.”

Inventor of the hexabundles and head of the Sydney Astrophotonic Instrumentation Laboratory (SAIL) labs, Professor Joss Bland-Hawthorn said SAMI provided spatially resolved data for many galaxies at once: “In the past, we have either targeted large numbers of galaxies at once – each with a single fibre – or observed many locations in a single galaxy at a time.”

Instrument lead, Dr Jon Lawrence said: “Combining the new hexabundles with existing infrastructure at the Anglo-Australian Telescope has allowed us to take a new and different look at galaxies.”

SAIL director Dr Sergio Leon-Saval said the hexabundle approach would be one of the main pillars of a CAASTRO-3D Centre of Excellence that he hoped would launch this year.

“The SAMI Galaxy Survey has been one of the main successes of the CAASTRO Centre of Excellence,” Dr Leon-Saval said. “We now have the capability to make even larger and different format hexabundles to enable new instrument concepts like Hector now under design.”

The Peter McGregor Prize is awarded every three years by the Astronomical Society of Australia in recognition of exceptional achievement or innovation in astronomical instrumentation. The prize is named in honour of the outstanding instrument builder Peter McGregor, who died in 2015.

The citation states the award was bestowed:

"to recognise the impressive development of the ‘hexabundle’ technology that has been the primary enabler for the SAMI instrument, representing a significant leap in capability for multi-object spectroscopy. This instrument has made possible a qualitatively new view of galaxy structure and formation, and the long-term impact is likely to continue to grow through ongoing observations, as well as future developments of new instruments based on further developments of the technology."

The SAMI instrument is based on astrophotonic developments from SAIL within the School of Physics at the University of Sydney, in collaboration with the Australian Astronomical Observatory (AAO).

The hexabundles were developed and tested in the Sydney Astrophotonic Instrumentation Lab before being installed into a prototype instrument developed by the University of Sydney and the AAO. 

Dr Julia Bryant, who led the development of the hexabundles, said “the fibres were packed and fused under carefully controlled temperature and pressure to maximize fibre throughput”.  The first SAMI observations were obtained in July 2011 and published in 2012.

SAMI has gone on to be used for a major five-year observational program using more than 250 nights of telescope time on the four-metre Anglo-Australian Telescope. It is already revealing new insights such as showing how galaxies are shaped by feedback from star formation and how galaxy structure is related to their rotation.

The instrument has inspired major overseas developments including the SDSS Manga Project and the ESO VLT Fireball Project.

Grants

The SAMI instrument has been supported by:

• ARC Federation Fellowship, FF0776384 (Bland-Hawthorn)
• ARC LIEF, LE130100198 (Bland-Hawthorn et al)
• ARC LIEF, LE150100144 (Bland-Hawthorn et  al)
• ARC Future Fellowship, FT100100457 (Croom)
• ARC Centre of Excellent for All Sky Astrophysics (CAASTRO), CE110001020 (Gaensler et al).