Violent galaxy seen in 3-D
Astronomers at the Gemini telescope in Hawaii have obtained a complete, multi-dimensional picture, of the dynamic flow of gas and stars at the core of an active galaxy [NGC 1068] located 70 million light years away. The image was achieved in a single snapshot and is the first time such a picture has been obtained by one of the new generation of giant telescopes with an 8 – 10 metre light collecting mirror. The astronomers used a new instrument – the Integral Field Unit (IFU), designed and built at Durham University – fitted to the telescope`s multi-object spectrograph to image the violent galaxy. The resulting data has been transformed into an animation that dramatically reveals the internal dynamics of the galaxy – including the interactions of a pair of galactic-scale jets that spew material for thousands of light years away from a suspected black hole at the galaxy`s core.
“We are very excited by these results and the superb capabilities that the IFU has added to the Gemini Multi-Object Spectrograph (GMOS)”, commented Dr. Jeremy Allington-Smith, from Durham University, who was responsible for the overall design and construction of the GMOS Integral Field Unit. ” In effect we have added an extra dimension to the main instrument so that it can physically map the motion of gas and stars at any point in the image of the object under study. So far we have used it to map the motion of gas within the nucleus of a powerful active galaxy, NGC1068, and the orbits of stars within more normal galaxies, but it can also be used to study regions within our own galaxy where stars are being formed.”
The IFU instrument uses hundreds of tiny optical fibres, each thinner than a human hair, with tiny micro-lenses attached to the end to guide light from the telescope`s two dimensional image to a spectrograph. The spectrograph produces one individual spectrum for each fibre, a total of 1500 individual spectra, that can each reveal details of the physical conditions and velocity of the gas, dust and stars that it observes. This technology is new to the world of 8 -10 metre class telescopes and is particularly powerful when combined with an advanced telescope like Gemini which has 10 times the light collecting power of the Hubble Space Telescope and uses sophisticated optical technologies to focus starlight to razor sharpness.
Dr. Gerald Cecil, of the University of North Carolina, recently studied this particular galaxy using the Hubble Space Telescope and believes that the new Gemini spectra will clarify many patterns revealed by Hubble. “Large ground-based telescopes like Gemini are the perfect compliment to Hubble because they can collect so much more light. But it`s critical to use all this light cunningly, and not throw most of it away as standard slit spectrographs do. Using the Gemini Multi-Object Spectrograph`s integral field capability allows us to perform detailed studies of the light to provide critical physical constraints on the nature of faint cosmic objects.” Dr. Cecil`s Hubble findings are to be published in the April 1 issue of the Astrophysical Journal.
“By using this technique we add an extra dimension to the data and can essentially make a movie with one click of the shutter,” says Dr. Bryan Miller, a Gemini astronomer working on Integral Field techniques. “When we play back our movie of the galaxy NGC1068, we see a 3-dimensional view of the core of this galaxy. It is striking how much easier it is to interpret features with this kind of data. With 3-dimensional views of galaxies we can determine mass distributions, true shapes, and hopefully their origins much more accurately than before.”
“The Gemini data of NGC 1068 reveal one of the lesser known features of galaxy jets,” explains Gemini North Associate Director Dr. Jean-Rene Roy. “For the first time we are able to clearly see the jet`s expanding lobe as its hypersonic bow shock slams directly into the underlying gas disk of the galaxy. It`s like a huge wave smashing onto a cosmic shoreline.”
The IFU instrument was designed and built in the UK at Durham University. Prof. Ian Halliday, Chief Executive of the Particle Physics and Astronomy Research Council, the agency responsible for funding UK astronomy said, ` The IFU will provide astronomers with a powerful new tool to probe the mysterious cosmic caldrons of the Universe, like those at the core of galaxies and stellar nurseries. The UK has almost a 25% share in the twin Gemini telescopes and it`s significant that British scientists have played such a major role in this innovative instrument. The entire team at Durham is to be congratulated. It clearly endorses the UK`s contribution to such international projects.`
The Integral Field Spectroscopy capabilities of the Gemini Observatory are still developing. Within the next two years both Gemini North on Hawaii and its Southern Hemisphere twin in Chile will have optical and near-infrared Integral Field Units. Some of these systems will work with adaptive optics to provide the highest spatial resolution images deliverable by the telescopes, including images in the infrared that will be sharper than can be produced by the Hubble Space Telescope at those wavelengths.
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