Post on 22-Dec-2015
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
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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
3 of 18Seminar Presentation, March 2012Primož Cigler
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
4 of 18Seminar Presentation, March 2012Primož Cigler
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 of 18Seminar Presentation, March 2012Primož Cigler
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 of 18Seminar Presentation, March 2012Primož Cigler
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
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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
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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
11 of 18Seminar Presentation, March 2012Primož Cigler
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 of 18Seminar Presentation, March 2012Primož Cigler
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)
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Spectrograph• Spectrograph uses transmissive diffraction gratings• Many gratings with different number of grooves/mm
can be used
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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 of 18Seminar Presentation, March 2012Primož Cigler
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 of 18Seminar Presentation, March 2012Primož Cigler
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
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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