1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 1.2-m UK Schmidt Telescope

10. Sample of photographic plate

11. 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

12. 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)

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

14. 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

15. 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
...

16. 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

17. 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

18. 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!