The Power of IR Adaptive Optics:
Astronomers from the University of Hertfordshire, in collaboration with Canadian colleagues from the Universite de Montreal, have obtained spectacular new images showing details not visible before in an active galaxy. They used the Adaptive Optics system on the 3.6-meter Canada-France-Hawaii Telescope atop Mauna Kea in Hawaii and a near-infrared camera to observe the central regions of galaxies. The new images obtained by Dr Johan H. Knapen and his group have a resolution several times better than is achievable without the use of adaptive optics, enabling them to separate the two components in the nucleus of the galaxy Markarian 273. They will show the images for the first time at the UK's National Astronomy Meeting at the University of Southampton.
The adaptive optics system used by Knapen and collaborators was developed to correct for distortions of astronomical images introduced by the Earth's atmosphere. In the night sky all stars twinkle, and it is this twinkling that astronomers do not like when they try to take long exposures and achieve sharp images. The adaptive optics system measures just how much the star, or galaxy, that is being observed twinkles, and corrects for the twinkling by adjusting a small mirror placed just before the infrared camera. The resulting images are as sharp as those taken with the Hubble Space Telescope.
Markarian 273 is an 'active' galaxy, producing radiation in its nucleus at such a rate that the output cannot be accounted for by stars alone. It may well harbour a black hole in its centre. The new near-infrared image clearly shows that the nucleus of the galaxy is actually double. 'We are probably witnessing the merger of two galaxies, whose nuclei we can still see' Knapen says. This process has set off the nuclear activity in one of the two nuclei. The new image is the first near-infrared image to show the two nuclei separately. Older images taken without an adaptive optics system can hardly resolve the two nuclei.
The resolution of the near-infrared image of Markarian 273 is around 0.2 seconds of arc. Markarian 273 is at a distance of around 150 megaparsec from us, or about 500 million light years. The two nuclei are separated by 1 second of arc, or around 700 parsec (2200 light years). The image was taken through a K-band filter centred at 2.2 microns.
The image can be copied from the following WWW site:
High-resolution near-infrared image of the nuclear region of the galaxy Markarian 273, obtained with the adaptive optics system on the Canada-France-Hawaii Telescope by a team of astronomers from the University of Hertfordshire and the Universit'e de Montr'eal (Canada). The galaxy has a double nucleus, whose two components are separated by 1 second of arc, or about 700 parsec (2200 light years). Photo credit: Dr J. H. Knapen, University of Hertfordshire.