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