Difference Image Analysis at OAC Groningen, 1st Dec 2004 AW-OAC team

Groningen, 1st Dec 2004 AW-OAC team The DIA is a software written by P.R.Wozniak based on the Alard & Lupton optimal PSF matching algorithm. The DIA is a software written by P.R.Wozniak based on the Alard & Lupton optimal PSF matching algorithm. DIA was originally created to search variable objects on the OGLE-II bugle microlensing data DIA was originally created to search variable objects on the OGLE-II bugle microlensing data The original version is not well documented (parameters optimization is not easy) and it is optimized for OGLE data The original version is not well documented (parameters optimization is not easy) and it is optimized for OGLE data We present a modified version that includes: We present a modified version that includes: –New tool to prepare the images using the astrometry –New functionalities in the core (masks, external domains) –Python interface to send processes on a BEOWULF cluster –New tool to study the candidates (ascii catalogues, light curves, frequency analysis, phase diagrams, stamps)

Groningen, 1st Dec 2004 AW-OAC team Overview: Original DIA Cross_regrid* Registration and correction of input images mstack Creation of the reference image with best seeing frames getpsf Global PSF on REF (used in getvar and phot steps) Aga ** Creates difference images Getvar ** Finds variable candidates Phot ** Light Curve with PSF and aperture photometry on the difference images * Not used in the new version ** New functionalities added

Groningen, 1st Dec 2004 AW-OAC team AGA step: Image Subtraction Once the reference frame ref.fits is created it is convoluted with a kernel (spatially variable in general) in order to match as close as possible each image. This convoluted image is then subtracted to the current frame, producing a serie of subtracted images. Once the reference frame ref.fits is created it is convoluted with a kernel (spatially variable in general) in order to match as close as possible each image. This convoluted image is then subtracted to the current frame, producing a serie of subtracted images. The Algorithm A list of objects is found on the REF (domains) A list of objects is found on the REF (domains) A list of objects is found on the single image (domains) A list of objects is found on the single image (domains) It matchs the domains and calculates the kernels (3 Gaussians of costant widths multipied by polynomials) It matchs the domains and calculates the kernels (3 Gaussians of costant widths multipied by polynomials) The best solution is taken to produce the difference image The best solution is taken to produce the difference image

Groningen, 1st Dec 2004 AW-OAC team Getvar step: variable objects detection Variable objects are detected using some preliminary variability measurements based on the entire serie of difference images for a given field. Final measurements are made only for these candidates. The program starts by rejecting some fraction of the frames with the worst seeing (in our case 10%) The pixel is declared as variable if one of these two conditions are met: 1. There are at least 3 consecutive points departing at least 3σ from the base line in the same direction (up or down), or 2. There are at least 10 points in total departing at least 4σ from the base line in the same direction, not necessarily consecutive. NB: The extension to other types of variables is straightforward!

Groningen, 1st Dec 2004 AW-OAC team Phot Step: Photometry For each variable object the program performs both profile and aperture photometry on difference images keeping the centroid fixed The format of the catalog is : 1. Flux – profile photometry 2. Flux error – profile photometry 3. Flux – aperture photometry 4. Flux error – aperture photometry 5. Background 6. FWHW of the PSF profile Where: Pi is PSF for pixel i fi flux for pixel i on differece images fi,0 flux for pixel on original images G is Gain and

Groningen, 1st Dec 2004 AW-OAC team New DIA Version: step 1 wcs2pix A C program that reads astrometric informations from the headers (CRVAL,CRPIX,CD) and through the WCS library finds the common part of the images. A C program that reads astrometric informations from the headers (CRVAL,CRPIX,CD) and through the WCS library finds the common part of the images. The WCS library is also used to extract the object coordinates in alfa e delta from the output files. The WCS library is also used to extract the object coordinates in alfa e delta from the output files.

Groningen, 1st Dec 2004 AW-OAC team New DIA Version: new functionalities Added in Aga: Mask for each input image Mask for each input image The kernel can be calculated using an external list of objects The kernel can be calculated using an external list of objects Added in Getvar: Ascii catalogs of variable objects Ascii catalogs of variable objects Psf image is created and saved (QC check) Psf image is created and saved (QC check) VAR and ABS images are saved (see ISIS) VAR and ABS images are saved (see ISIS) Added in Phot: Ascii light curves with phases Ascii light curves with phases

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Software Hardware The New DIA Version: how it works on the BEOWULF Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 1: cut all images using the astrometric solution Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 2: split the images in sub frames and copy them on nodes Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 3: mstack the subframes indipendently on the nodes Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 4: getpsf Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 5: aga Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 6: getvar Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 7: phot Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team BeoRunner wcs2pix prepare mstack getpsf aga getvar phot MASTER Node 2 Node 1 Node n lc storage Step 8: lc Network SWITCH

Groningen, 1st Dec 2004 AW-OAC team LC Step: Analysis of the results For each variable candidate the software produces a light curve in a file called LC_NAMEFIELD_Xpixel_Ypix_alfa_delta-subframe.data An automatic Fourier transform is done and an ascii file is created with frequency, power and s/n ratio (power/standard deviation). This file is called as the LC file plus Max=…_fre=…_sn=… in order to have the main informations directly in the filename. The frequency of the max peak is used to add a phase column.

Groningen, 1st Dec 2004 AW-OAC team The format of the LIGHT CURVE 1. Flux – profile photometry 2. Flux error – profile photometry 3. Flux – apeture photometry 4. Flux error – aperture photometry 5. Background 6. FWHM of the PSF Profile 7. MJD-OBS 8. PHASE Where: Pi is PSF for pixel i fi flux for pixel i on differece images fi,0 flux for pixel on original images G is Gain and

Groningen, 1st Dec 2004 AW-OAC team 692kx2k157kx7k468kx9k wcs2pix1m14m prepare1m3m21m mstack3s10s1m10s getpsf2s5s10s aga3m3m50s19m31s Getvar*10s14s1m37s Phot * 3s10s1m7s Lc*8s12s1m TOTAL4m26s8m42s59m35s TESTs 69 Images VLT-FORS – GC 2kx2k B Band 69 Images VLT-FORS – GC 2kx2k B Band 46 Images WFI – Carina 8kx9k B Band 46 Images WFI – Carina 8kx9k B Band 15 Images WFI – OACDF 7kx7k V Band 15 Images WFI – OACDF 7kx7k V Band Beo2 – 1 Master + 16 nodesBeo0/1 – 2 Master + 8 nodes692kx2k157kx7kwcs2pix1m15s prepare2m8m mstack10s37s getpsf7s12s aga4m20s5m23s Getvar*1m11s1m59 Phot*59s1m32 Lc*2m1m TOTAL6m47s19m58 * it depends from the threshold in Getvar

Groningen, 1st Dec 2004 AW-OAC team VLT-FORS Images

Groningen, 1st Dec 2004 AW-OAC team VLT-FORS Image VLT-FORS difference Image

Groningen, 1st Dec 2004 AW-OAC team Light curves: VLT-FORS

Groningen, 1st Dec 2004 AW-OAC team Light curves: VLT-FORS

Groningen, 1st Dec 2004 AW-OAC team Light curves: WFI-Carina

Groningen, 1st Dec 2004 AW-OAC team Light curves: WFI-Carina

Groningen, 1st Dec 2004 AW-OAC team Light curves: WFI-Carina

Groningen, 1st Dec 2004 AW-OAC team An object from the OACDF An object from the OACDF

Groningen, 1st Dec 2004 AW-OAC team Other Light curves from FORS data Other Light curves WFI-CARINA data

Groningen, 1st Dec 2004 AW-OAC team Open Points: Improve the throughput in the preparation steps Improve the throughput in the preparation steps Photometry (PSF, aperture on original images) and relative amplitudes. Photometry (PSF, aperture on original images) and relative amplitudes. User Manual User Manual AW integration AW integration