
Extracting the Mystery from the Red Rectangle Meghan Canning, Zoran Ninkov, and Robert Slawson Chester Carlson Center for Imaging Science Rochester Institute of Technology
Overview • Research Objectives • Background • Methodology • Progress To Date • Further Investigation • Conclusions
Objectives • Short Term • To Accurately Model and Remove Stellar Objects from Spectrophotometric Images of Emission Nebula by Way of Profile Fitting • Long Term • To Characterize the Extended Emission Present in the “Red Rectangle”
Emission Nebula • Red Rectangle • Star HD44179 • Biconical nebula • X-shaped pattern in red region of visible spectrum
Optical Spectroscopy Emission Nebula
Methodology • Acquire spectrophotometric images of Red Rectangle • Fit a point spread function to nebula’s central star at reference wavelength (525 nm) • Remove profile from images corresponding to spectral emission lines of interest
Image Acquisition • UTSO 60 cm telescope • Front-illuminated Kodak KAF-4200 CCD inside Photometrics CH-250 camera head
Image Acquisition • Cambridge Research & Instrumentation, Inc. Varispec Tunable Liquid Crystal Filter • Fixed spectral bandwidth of 10 nm • Central wavelength tunable between 400 and 700 nm • 31% transmittance at 700nm; 5% at 435nm
Spectral Characteristics Image 2 - 638 nm Image 1 - 525 nm Exposure time = 800 sec Exposure time = 400 sec
Methodology • Find coordinates of peak intensity of like objects in Image 1 & Image 2 • Calculate scaling with respect to intensity of Red Rectangle in Image 1 • Fit appropriately scaled PSF • Subtract profile from coordinates of peak intensity
Processing • Image Reduction Analysis Facility • DAOPHOT package (NOAO/Tuscon) • DAOFIND - locates coordinates of peak intensity • PHOT - calculates photometry parameters • PSF - Fits a point spread function • ALLSTAR - Removes psf from stellar objects
Object Red Rectangle 525nm Faint Star 525nm Red Rectangle 638nm Peak Intensity PSF Scale Factor 6279.226 1.0000 2602.09 1.2430 7837.154 0.4144 Photometry Parameters
Imaging • Fit Gaussian Profile at 525 nm • FWHM = 10 pixels • PSF radius = 37 pixels Pixel Value Column (pixels)
Profile Testing • Does the psf accurately model the central star at 525 nm? • Can the psf be accurately scaled to fit other stellar objects: • within the 525 nm frame? • in frames recorded at 638 nm?
PSF Removal - Central Star =525 nm Pixel Value Column (pixels)
PSF Removal - Faint Star =525 nm Pixel Value Column (pixels)
PSF Removal - Red Rectangle • Reconstructed Image of Nebulosity at = 638 nm
Red Rectangle - 638 nm Pixel Value Pixel Value Column (pixels) Red Rectangle -Reconstructed Column (pixels)
Analysis • Virtually Faultless Removal of psf from central star in Image 1 • Only Poisson noise from fit remaining • Removal of psf from faint stellar object in Image 1 results in a small peak intensity (~250) surrounded by a negative “dip”
Analysis • PSF is not good enough • Fit is too small at the peak intensity; too bright in the wings • May be some emission at 525 nm causing an inaccurate fit to the central star • Consequently -extended emission at 638 nm is inadequately reconstructed
Further Investigation • Fit psf to an average profile taken from several stars in Image 1 • Small FOV - OTF constant over frame • Apply profile testing methods • Verify registration/centering accuracy
Conclusions • Many variables involved in psf fitting • Encouraging Beginning • Further testing of psf accuracy and centering algorithms must be completed before success in generating a representation of the extended emission can be achieved