Effectiveness of detection and simulation of supernovæ

To determine the effectiveness of our chain of detection and to test the various stages of the reduction, we developed in ToADS of the tools for simulation, which from the only images, are able to simulate supernovæ.

To be realistic, this simulation was conceived to add false supernovæ before even the rééchantillonage of the images.

The various stages are:

1. Selection of `` beautiful '' stars on one of the component images of the image of research.

2. Selection of the galaxies hosts on which false the supernovæ will be simulated in the range magnitude that one wants to study.

3. Definition of displacement necessary to bring star nearest on the galaxy considered. These displacements are in whole number of pixels to avoid having with rééchantillonner stars.

4. Standardization of the flux of star to bring it to a fraction of the flux of its galaxy host.

5. One stores flux (magnitude) and position of false the supernovæ in a list.

6. Detection is entirely turned over (rééchantillonage-coaddition-subtraction-detection). It is significant in this stage to have preserved the transformations and the core of convolution of detection without supernovæ, the presence of a too great number of simulated objects completely which can distort their determination.

7. One compares the objects detected with the objects simulated to build the operating characteristics.

Figure 7.21 shows a simulation carried out on the images of research (3h for the images of reference and 3h for the images of research out of I) of countryside CFHT of spring 2001. It is seen that the effectiveness of detection exceeds the 90% for a magnitude of 24.5. This operating characteristic is in concord with the estimated curves limiting magnitudes of figures 7.5 .

Figure 7.21: Operating characteristic of detection in filter I according to the magnitude (Vega). This operating characteristic was built on the same images as for the detection of the supernovæ of the research campaign of spring 2001. 1000 supernovæ were simulated on the CCD 10 of the D4 field observed with the CFH12K out of I This figure in agreement with simulations limiting magnitude presented higher shows than it is possible to detect with an effectiveness higher than 90% of the supernovæ magnitude out of I higher than 24.5, this magnitude corresponds to a supernova of the Ia type to its maximum of light to a redshift of 1.2