Spectroscopy Techniques and Projects at 1.2-m UK Schmidt Telescope Author: Primož Cigler Mentor: prof. dr. Tomaž Zwitter Seminar Leader: prof. dr. Peter Križan

What I will be talking today about? Two parts Basics about spectroscopy and some theoretical background The Australian Astronomical Observatory, UK Schmidt Telescope and research projects

Spectroscopy - Prism Light can be dispersed into the spectrum in different ways The best known method is using the prism Refractive index n in function of wavelength λ Problem: values of refractive index for glass ~1 To so komentarji

Spectroscopy - Gratings A more divergent beam can be achieved by using diffraction grating comparing to prism There are two different types of gratings – reflective and transmissive Gratings work based on the constructive interference Transmissive more commonly used, no problems with dirt

Application of Optical Fibers Optical fibers are very important nowadays for leading the light from the focal plane of the telescope to the spectrograph Multiple objects can be captured at the same time Fibers must be properly positioned in the focal plane, so the light from the certain object is focused in the end of the fiber

Australian Astronomical Observatory Australian Astronomical Observatory operates within the Siding Spring Observatory near town Coonabarabran, NSW, Australia Located about 1150 m above the sea level and 330 km NW of Sydney

Australian Astronomical Observatory Location provides extraordinary observational conditions regarding the darkness and clarity of the sky The first building of the telescopes took place in 1967, mainly because there are many very interesting objects visible exclusively from southern hemisphere Australian Astronomical Observatory operates two telescopes: Anglo-Australian Telescope UK Schmidt Telescope

1.2-m UK Schmidt Telescope The telescope was build in 1973 for purpose of southern sky surveys – to photograph the whole southern night sky Unique optical design – Schmidt camera – which provides stunning 6.6 × 6.6 degrees field of view, captured with 14 × 14 inch (356 × 356 mm) photographic plates

1.2-m UK Schmidt Telescope

Sample of photographic plate

6dF (6-degree Field) In 2001 the telescope was upgraded with 6dF 6dF is a multi-object spectroscopy system It uses an off-telescope robotic fiber positioner to configure up to 150 fibers

6dF (6-degree Field) 6dF was used for Galaxy Survey between 2001 and 2005, measuring the redshift for 120,000 galaxies Since 2005 the telescope has been exclusively used for RAVE (RAdial Velocity Experiment)

Spectrograph Spectrograph uses transmissive diffraction gratings Many gratings with different number of grooves/mm can be used

RAVE Project RAdial Velocity Experiment is about to be accomplished this year, running since 2003 on 1.2-m UKST Almost 600,000 stellar spectra will be obtained at the end of the project A lot of new data about the stars: radial velocity, stellar parameters, distances etc

What information do the spectra contain? Most of what we know today about the distant celestial objects is based on spectroscopy Radial velocity of stars or galaxies can be determined to accuracy of 1 m/s (HARPS) nowadays Star‘s characteristics can be calculated: Effective temperature Metallicity / chemical composition of the star Gravitational acceleration on the surface of the star ...

Why Multi-Object Spectroscopy? About 300 billion stars in our galaxy Milky Way About 500 billion galaxies in the Universe For creating the representative sample a large number of spectra must be obtained Classical method allows just one object being captured at the time, demanding up to an hour of exposition

Multi-Object Spectroscopy Projects Multi-object spectroscopy is very promising branch of astronomy with many ongoing projects: FLAIR (1980s) – 90 objects 2dF (1997) – 392 objects 6dF (2001) – 150 objects GMOS (2001) – several hundreds of objects LAMOST (2007) – 4000 objects

Thank you for your attention! Acknowledgements Special thanks goes to the following people: Tomaž Zwitter (for arranging the visit of UK Schmidt Telescope) Paul Cass (for presenting the UKST and 6dF) Thank you for your attention!