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Issued by: Inge Heyer, Science Outreach Specialist Images, notes, and contact details appear below. 30 October 2008 James Clerk Maxwell Telescope Searches the Dark Hearts of Bright GalaxiesUsing the James Clerk Maxwell Telescope (JCMT), astronomers from the Netherlands, the United Kingdom and Germany have obtained important information on some of the most spectacular objects in the present-day universe. Ultraluminous Infrared Galaxies (ULIRGs) are characterized by an enormous energy output, which is totally hidden from view for optical telescopes by massive gas and dust clouds inside these galaxies. When the universe was much younger, such galaxies were much more common than now, and scientists believe that galaxies of this type have played a key role in shaping the present-day universe. Their enormous energy output is attributed to extremely rapid conversion of the available gas into young, luminous stars, and to energetic processes associated with supermassive black holes. Astronomers Kate Isaak (Cardiff University, United Kingdom), Paul van der Werf (Leiden University, The Netherlands) and Padeli Papadopoulos (Bonn University, Germany) have recently used the JCMT to probe the physical conditions in the active inner regions of a number of ULIRGs directly. Dr Papadopoulos says: "The submillimetre radiation observed by the JCMT can penetrate the dust shroud obscuring the nuclear regions of the ULIRGs, but the spectral lines emitted from these regions are still very faint. Therefore, we had to use the JCMT and its sensitive HARP receiver for up to 12 hours under very good atmospheric conditions, to detect just a single line in a single galaxy." "These spectra are among the deepest ever obtained with the JCMT", says Professor Gary Davis, the Director of the James Clerk Maxwell Telescope. "They demonstrate the extraordinary sensitivity of HARP, our new, state-of-the-art receiver. It is rewarding to see new science discoveries emerging which would previously have been impossible." Dr Isaak says: "Even future satellites will not be able to supply us with all the information we need to probe the conditions within these galaxies: the JCMT with its large collecting area provides essential pieces in the puzzle." Among the molecular fingerprints that the team has observed are spectral lines of warm and dense carbon monoxide (CO) and of the formyl ion (HCO+). However, the most prized spectral line observed by the team is hydrogen cyanide (HCN). This line originates from warm, dense (and highly toxic) hydrogen cyanide gas in the most active regions of the ULIRGs. These are the first spectra of this type from a substantial set of ULIRGs, and they have been proven to be surprisingly difficult to detect in many of these extreme objects. When interpreted together with the rest of the data, it becomes obvious that this spectral line probes the most extremely dense gas, the very immediate fuel of the massive star formation in these objects. As Dr van der Werf explains: "Unlike other spectral lines which probe more remote gaseous regions in these galaxies which may not be actively forming stars, the hydrogen cyanide intensity changes dramatically from galaxy to galaxy. This depends on, and reveals, the intense gravitational tides and their effects on the densest of the gas phases in the centres of the ULIRGs." Dr Antonio Chrysostomou, Associate Director of the James Clerk Maxwell Telescope, says: "To try and place these observations in context, keep in mind that these photons had to traverse not only across their host galaxies but also over 500 million light years of inter-galactic space before reaching our Galaxy. Then consider that when they arrive at the Earth, the energy they carry is no larger than six- to three-thousandths of a degree Centigrade, and for us to be able to detect this energy our instrumentation needs to be at least three times more sensitive still." The team is currently continuing its study of ULIRGs with the JCMT by observing gas that is dense and hot, and therefore even more directly associated with the formation of young stars. This requires not only the large collecting area of the JCMT and the most favorable observing conditions, but also the newly commissioned very high frequency receiver W/D operating at 690 GHz, one of the highest frequencies that can be observed from the ground. This is possible from only very few places on the planet. Mauna Kea, with its commanding heights and the extremely dry conditions that can occur there, is one of those places where such observations are possible. Images
Spectrum of HCO+(4-3) in the ULIRG Mrk231 (which is located at a distance of 570 million light years from the Milky Way), obtained with the JCMT and its HARP receiver. The background image shows Mrk231 as observed with the ACS on board the Hubble Space Telescope (credit: NASA, ESA, the Hubble Heritage STScI/AURA-ESA/Hubble Collaboration, and A. Evans, University of Virginia, Charlottesville/NRAO/Stony Brook University). The bright peak in the center of this galaxy reveals the presence of an active nucleus, possible powered by a supermassive black hole formed in the dense obscuring dust layer.
Spectrum of HCN(4-3) in the ULIRG UGC5101 (which is located at a distance of 530 million light years from the Milky Way), obtained with the JCMT and its HARP receiver. The background image shows UGC5101 as observed with the ACS on board the Hubble Space Telescope (credit: NASA, ESA, the Hubble Heritage STScI/AURA-ESA/Hubble Collaboration, and A. Evans, University of Virginia, Charlottesville/NRAO/Stony Brook University). In this image the dust clouds obscuring the most luminous parts of the galaxy can be seen as a red-brown band.
The James Clerk Maxwell Telescope on Mauna Kea, Hawaii.
ACSIS being tested in the lab in Canada.
HARP on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii.
Notes for EditorsLight YearOne light year is about 10 million million kilometres or 6 million million miles. Sub-millimetre LightSub-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 10000th of a centimetre, or one 25000th of an inch. GHzThe gigahertz (GHz) is a unit of alternating current or electromagnetic wave frequency equal to one billion hertz. The gigahertz is used for frequencies of ultra-high-frequency (UHF), microwave and submillimetre signals. A signal having a frequency of 1 GHz has a wavelength of 300 millimeters, or a little less than a foot. JCMTThe 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. More about the James Clerk Maxwell Telescope: http://outreach.jach.hawaii.edu/articles/aboutjcmt/ HARPHARP (Heterodyne Array Receiver Programme) is an array of 16 spectral receivers, arranged in a 4x4 grid and using superconducting junctions as the detector elements. ACSIS (AutoCorrelation Spectrometer and Imaging System) is a system of high-speed digital electronics and computers for analysing the signals produced by HARP and other instruments. It contains more than 1000 customised chips and 30 microprocessors for handling the high data rate and producing results in a form that astronomers can use. ACSIS produces data at a rate 1000 times faster than the old JCMT system. Together these instruments have turned the JCMT into a sub-millimetre-wave 3-D camera rather than just a single-point telescope. HARP is a collaboration between the Mullard Radio Astronomy Observatory (MRAO) in Cambridge, UK, the Herzberg Institute of Astrophysics at the Dominion Astrophysical Observatory in Canada (NRC-HIA), the Joint Astronomy Centre in Hilo, Hawaii (operators of the JCMT), and the United Kingdom Astronomy Technology Centre (part of the Science and Technology Facilities Council) in Edinburgh. ACSIS is a collaboration between the Herzberg Institute of Astrophysics at the Dominion Radio Astrophyical Observatory in Canada (NRC-HIA), the Joint Astronomy Centre and the United Kingdom Astronomy Technology Centre. SIS junctions designed by MRAO were fabricated under contract by The TU Delft Institute of Microelectronics and Silicon Technology (DIMES). The UK ATCThe UK Astronomy Technology Centre is located at the Royal Observatory, Edinburgh (ROE). It is a scientific site belonging to the Science and Technology Facilities Council. The mission of the UK ATC is to support the mission and strategic aims of the Science and Technology Facilities Council and to help keep the UK at the forefront of world astronomy by providing a UK focus for the design, production and promotion of state of the art astronomical technology. Science and Technology Facilities CouncilThe Science and Technology Facilities Council is an independent, non-departmental public body of the Office of Science and Innovation which itself is part of the Department of Innovation, Universities and Skills. It was formed as a new Research Council on 1 April 2007 through a merger of the Council for the Central Laboratory of the Research Councils (CCLRC) and the Particle Physics and Astronomy Research Council (PPARC) and the transfer of responsibility for nuclear physics from the Engineering and Physical Sciences Research Council (EPSRC). We are one of seven national research councils in the UK. The Science and Technology Facilities Council is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Organisation for Nuclear Research, CERN, the European Space Agency and the European Southern Observatory. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility. National Research Council CanadaThe National Research Council (NRC) is the Government of Canada's premier organization for research and development. It reports to Parliament through the Minister of Industry. It is governed by a council of 22 appointees drawn from its client community. NRC is responsible for, among other things, undertaking, assisting or promoting scientific and industrial research in different fields of importance to Canada, operating and administering any astronomical observatories established or maintained by the Government of Canada, administering NRC's research and development activities, including grants and contributions used to support a number of international activities, and providing vital scientific and technological services to the research and industrial communities. This mandate is discharged to a great extent through the operation of the NRC Industrial Research Assistance Program, the NRC Canada Institute for Scientific and Technical Information and the Canadian Technology Network. Netherlands Organisation for Scientific ResearchThe Netherlands Organisation for Scientific Research (NWO) funds thousands of top researchers at universities and institutes and steers the course of Dutch science by means of subsidies and research programmes. NWO is responsible for enhancing the quality and innovative nature of scientific research as equally initiating and stimulating new developments in scientific research, mainly fulfils its task by allocating resources, facilitates, for the benefit of society, the dissemination of knowledge from the results of research that it has initiated and stimulated, and mainly focuses on university research in performing its task. In fulfilling its responsibilities NWO pays due attention to the aspect of coordination and facilitates this where necessary. NWO wants to ensure that Dutch science continues to be amongst the best in the world and that the currently strong position is further strengthened. Media ContactsPlease note that it is best to contact these individuals by email.
Science ContactsPlease note that it is best to contact these individuals by email.
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