1 of 18 Seminar Presentation, March 2012Primož Cigler Spectroscopy Techniques and Projects at 1.2-m...

1 of 18Seminar Presentation, March 2012Primož Cigler

Spectroscopy Techniques and Projects at 1.2-m UK Schmidt Telescope

Author: Primož CiglerMentor: prof. dr. Tomaž ZwitterSeminar Leader: prof. dr. Peter Križan


What I will be talking today about?

Basics about spectroscopy and some theoretical

background

The Australian Astronomical

Observatory, UK Schmidt Telescope and

research projects

Two parts


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


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 ProjectsMulti-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


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!

1 of 18 Seminar Presentation, March 2012Primož Cigler Spectroscopy Techniques and Projects at 1.2-m...

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