Eli KasaiNASSP Masters 2011

UCTSAAO

Thesis: SN Ia Rate in Intermediate-Redshift Galaxy Clusters

Supervisor: Dr Steve CrawfordCo-supervisor: Prof Bruce Bassett

OUTLINE

SN Ia rate measurement• Importance

Physical Processes• Single and Double degenerate

Image Subtraction Algorithm• IRAF

Automated Image Subtraction Algorithm• ISIS (Alard & Lupton, 1998)

Importance SN Ia rate measurements

Progenitor Models Delay Time Distribution

Iron Abundance in the ICM

Intra-cluster stellar component tracer

Cosmology• Improved cosmological parameters

Physical Processes

Image Subtraction Algorithm – IRAF

Measure FWHM of few stars

Convolve images to seeing of worst frame

tw05.R186.1001.fits > conv_tw05.R186.s23.fits

Image Subtraction Algorithm – IRAF cont...

tw05.R128.1004.fits > conv_tw05.R128.1004.s23.fits

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

Image Subtraction Algorithm – IRAF cont...

Subtract scaled convolved reference from each convolved image

Normalize difference image with Poisson fluctuations > S/N image

Automated Subtraction Algorithm – ISIS

Measure FWHM of few stars - IRAF

Crop out common area > 3600 x 3600 - Python script

Automated Subtraction Algorithm – ISIS cont...

Produce 900 x 900 cutouts (for MS0451) – Python script

Apply automated subtraction steps

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

Automated subtraction steps – ISIS cont...

Mosaic the sub-images to produce complete difference image – Python script

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”

Transients found by both Algorithm in the same images

Top row: Iraf Algorithm Bottom row: ISIS algorithm

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

THANK YOU

References

Alard C. & Lupton, R. H. 1998, ApJ, 503, 325

Alard, C. 2000, A&A, 144, 363

Barbary et al. 2011, arXiv:1010.5786v3

Dilday et al. 2010, ApJ, 715, 1021

Maoz & Avishay 2004, MNRAS, 347, 951

Sand et al. 2008, AJ, 135, 1917

Sharon et al. 2010, ApJ, 718, 876