Outline of Work Undertaken With The AAT
The AAO has undertaken pioneering work on the use of optical fibres in astronomy for over 25 years. Instruments such as AAOmega and its predecessor 2dF, use optical fibres to feed the light of stars and galaxies from the focal plane of the telescope (i.e. where it forms an image of the night sky) into a spectrograph where it is smeared out into its component colours for detailed subsequent analysis. The broad field-of-view accessed by the 2dF and AAOmega instruments (4 times the width of the moon) and their 400 optical fibres, makes it feasible to spectroscopically survey large numbers of objects distributed across expansive areas of sky in a reasonable time frame.
A number of major studies undertaken with the AAT have exploited these capabilities. The 2dF Galaxy Redshift Survey (2dFGRS) used the 2dF instrument to obtain spectra and redshifts for ~250000 galaxies brighter than B~19.5 over ~7% of the southern sky in only ~270 nights. The 2dFGRS sample size was an order of magnitude greater than those of previous surveys, allowing a rigorous evaluation of cosmological parameters. For example, the survey has refined estimates of the mass density of the Universe, provided a determination of the fraction of baryonic (i.e. normal) matter in the Universe and set an upper limit on the total mass of neutrinos. In addition 2dFGRS yielded an independent estimate of the Hubble constant, which was in excellent agreement with value determined by the Hubble Space Telescope Key Project
The ongoing WiggleZ project is using the AAT and AAOmega to measure the redshifts of ~200000 distant luminous blue star forming galaxies distributed over an area of ~5000 times the area of the moon. The primary goal of this study is to use an intrinsic feature in the distribution of galaxies as a “standard ruler” to relate distance to redshift and improve our knowledge of the nature of dark energy. This mysterious component of the Universe appears to be responsible for accelerating its rate of expansion.
Another current AAOmega based survey on the AAT, Galaxy and Mass Assembly (GAMA), is in the process of obtaining optical spectroscopy for ~250000 galaxies in the Local Universe. The AAOmega data will be used in conjunction with observations from satellite observatories (e.g. Herschel Space Observatory) and other telescopes around the world (e.g. the European Southern Observatory's Visible and Infrared Survey Telescope, VISTA) to critically examine the predictions of the Cold Dark Matter standard cosmological model e.g. the relationship between the number density of dark matter halos and their masses and the relationship between the number density of galaxies and their masses as determined through studying their starlight.
The AAT also hosts an ongoing program to search for extrasolar planets, the Anglo-Australian Planet Search (AAPS). The AAPS exploits the high stability of the University College of London Echelle Spectrograph (UCLES) to obtain the few meters per second precision in measurements of the radial (line-of-sight) velocities of stars necessary to detect the reflex Doppler motion induced by the presence of a planet. To date the AAPS has found more than 20 extrasolar planets, with masses ranging from ~10% to > 10 times that of Jupiter.
Read more about this topic: Australian Astronomical Observatory
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