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De-Fringing Michelle Spectra Through Fourier

Filtering GEMINI NORTH TELESCOPE

HILO, HAWAII

INTERN: MEGAN ANSDELLADVISOR: SCOTT FISHER

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MICHELLE

• Facility imager and high-resolution spectrometer• Mid-Infrared (7-26 microns)

• Dust, comets, planet forming disks, black holes

• Cold Objects (300-500K)

• IR spectrum used to study mineralogy and composition

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INTERFERENCE WITHIN DETECTOR

BACKGROUND FRINGES ON SPECTRA

FOURIER FILTERING

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FOURIER FILTERING

• DOESN’T DISTORT SIGNAL

• MATHEMATICAL PROCESS THAT REMOVES FRINGES

• FREQUENCY DOMAIN

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SPATIAL DOMAIN

SHORT λ LONG λ

} SIZE OF OBJECT

A RAW SPECTRUM FROM MICHELLE

(what we see at the telescope)

OBJECT SIZE

.

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FREQUENCY DOMAIN

POWER SPECTRUM (same data, Fourier transformed)

Scott Fisher, Spatial Domain

Scott Fisher, Frequency Domain

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FOURIER TRANSFORM

MICHELLE SPECTRUM (Spatial Domain)

POWER SPECTRUM (Frequency Domain)

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CREATING THE MASK

POWER SPECTRUM(frequency domain)

THE MASK(symmetrical)

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REVERSE-FOURIER TRANSFORM

MASKED POWER SPECTRUM

DE-FRINGED SPECTRUM(Spatial Domain)

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SEEING THE DIFFERENCE

BEFORE AFTER

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THE PROJECT

• Available on Gemini North website

• Make Fourier Filtering of high-resolution MICHELLE spectra as easy as the click of a few buttons

• Use IDL (Interactive Data Language) to write program and GUI (Graphical User Interface)

• Distribute to researchers who acquire MICHELLE spectra

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Interactive Data Language

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EXPERIMENTAL PROGRAM

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FINAL PROGRAM

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• Distributed to anyone who acquires MICHELLE spectra from Gemini

• Available to download from Gemini North website

• Can be modified for use on any spectral data

THE FUTURE

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ACKNOWLEDGEMENTS

I would like to recognize Scott Fisher at Gemini North Observatory in Hilo for

donating his time and expertise to guide me through this project. Thanks

to Sarah Anderson, Malika Bell and everyone at CfAO in Santa Cruz for

making this internship possible. This work has been funded in part by the

National Science Foundation.