Extracting the Mystery from the Red Rectangle Meghan Canning, Zoran Ninkov, and Robert Slawson...
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Transcript of Extracting the Mystery from the Red Rectangle Meghan Canning, Zoran Ninkov, and Robert Slawson...
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
Emission Nebula
– Optical Spectroscopy
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
Exposure time = 800 sec
Image 1 - 525 nm Image 2 - 638 nm
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
Photometry Parameters
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
Imaging
• Fit Gaussian Profile at 525 nm
– FWHM = 10 pixels– PSF radius = 37
pixels
Column (pixels)
Pix
el V
alu e
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
Column (pixels)
Pix
el V
alu
e
PSF Removal - Faint Star =525 nm
Column (pixels)
Pix
el V
alu
e
PSF Removal - Red Rectangle
• Reconstructed Image of Nebulosity at = 638 nm
Red Rectangle - 638 nm
Red Rectangle -Reconstructed
Column (pixels)
Pix
el V
alu e
Column (pixels)
Pix
el V
alu e
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