SN Ia Rate in Intermediate-Redshift Galaxy Clusters - Eli Kasai
1. Eli Kasai
NASSP Masters 2011
UCT
SAAO
Thesis: SN Ia Rate in Intermediate-Redshift
Galaxy Clusters
Supervisor: Dr Steve Crawford
Co-supervisor: Prof Bruce Bassett
2. OUTLINE
SN Ia rate measurement
• Importance
Physical Processes
• Single and Double degenerate
Image Subtraction Algorithm
• IRAF
Automated Image Subtraction Algorithm
• ISIS (Alard & Lupton, 1998)
3. Importance SN Ia rate measurements
Progenitor Models
Delay Time Distribution
Iron Abundance in the ICM
Intra-cluster stellar component tracer
Cosmology
• Improved cosmological parameters
7. Image Subtraction Algorithm – IRAF cont...
Scale flux of convolved reference frame to match the rest
of the convolved frames
Flux conv_tw05.R186.1001.s23.fits = Flux conv_tw05.R128.1004.s23.fits
8. Image Subtraction Algorithm – IRAF cont...
Subtract scaled convolved reference from each convolved image
Normalize difference image with Poisson fluctuations > S/N image
9. Automated Subtraction Algorithm – ISIS
Measure FWHM of few stars - IRAF
Crop out common area > 3600 x 3600 - Python script
11. Automated Subtraction Algorithm – ISIS cont...
interp.csh
image registration – match coordinates to reference frame
ref.csh
composite reference frame
subtract.csh
mrj_phot C code, convolution kernel modeling, difference images
detect.csh
normalize subtracted images with photon noise
find.csh
positions of candidate transients
phot.csh
light curve production
12. Automated subtraction steps – ISIS cont...
Mosaic the sub-images to produce complete difference
image – Python script
13. Automated Subtraction Algorithm – ISIS cont...
Left: difference sub-image
Centre: difference sub-image normalized by poisson fluctuations
Right: positions of variables located by “find.csh”
14. Transients found by both Algorithm in the same images
Top row: Iraf Algorithm
Bottom row: ISIS algorithm
15. Comparison of the algorithms,
Left – IRAF; Right – ISIS
Time span from image convolution to differencing
IRAF algorithm ~ 1 week
ISIS automated algorithm ~ 3 - 4 hours