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Photometry with technique of Template Subtraction: personal experience .

Photometry with technique of Template Subtraction: personal experience. Stefano Valenti Physics Department of Ferrara – INAF Astronomical Observatory of Capodimonte Padova-Asiago Supernova Group ( http://web.pd.astro.it/supern/ ). Aperture Photometry Isolated object

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Photometry with technique of Template Subtraction: personal experience .

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  1. Photometry with technique of Template Subtraction: personal experience. Stefano Valenti Physics Department of Ferrara – INAF Astronomical Observatory of Capodimonte Padova-Asiago Supernova Group (http://web.pd.astro.it/supern/)

  2. Aperture Photometry Isolated object Photometry with PSF Fitting Not isolated object measure the PSF Fit the object with the PSF Other techniques Mark A sn2004gt

  3. PSF ----------------------------------------------------------- on GRAPHIC display > a < to accept star, > d < to delete on IMAGE display > f < to fit PSF, > w < to write PSF fit, > q < to quit --------------------------------------------------------------- Computing PSF for image: temp_SN97ab_281299_R 9 stars read from temp_SN97ab_281299_R.mag Star 1 rejected by user Star 2 has been added to the PSF star list X: 380.00 Y: 166.00 Mag: -7.644 Dmin: 6078.78 Dmax: 36255.29 …... Star 9 has been added to the PSF star list X: 395.00 Y: 827.00 Mag: -4.913 Dmin: 6067.815 Dmax: 8494.79 8 PSF stars read from temp_SN97ab_281299_R.mag Fitting function gauss norm scatter: 0.02782232 Analytic PSF fit Function: gauss X: 375. Y: 537.5 Height: 135507.7 Psfmag: -7.644 Par1: 2.375538 Par2: 1.847269 Computed 1 lookup table(s) Writing PSF image temp_SN97ab_281299_R.psf.fits Writing output PSF star list temp_SN97ab_281299_R.pst Writing output PSF star group file temp_SN97ab_281299_R.psg PSF (noao.digiphot.daophot.psf) allstar (noao.digiphot.daophot.allstar) PSF, Magnitude of field stars, Aperture correction ecpsf (package of SNOOPY) Cappellaro & Patat – Ledan software

  4. PSF PHOTOMETRY OF SN allstar (noao.digiphot.daophot.allstar) PSF used for the fit Difference image Residual image >>> input file ? (sn04gt_030105_R): >>> reference FWHM ? (10.): >>> aperture correction (ap-fit) ? (0.023): ************ background fit ********************** >>> mark corners of bg-region with >b<, exit >q< Type b again to draw box. >>> Order of function in x for bg fit ? (7): >>> Order of function in y for bg fit ? (7): >>> background fit OK ? (yes): >>> recentering for targets ? (yes): >>> Iterate on background ? (no): >>> Not yet happy ? Wish to adjust manually stellar peak ? (no): >>> Errors estimate (through artificial star experiment ?) (no): ************************************************************ #id x_ori y_ori x y ap_ori ap_bgsub fit_mag err_art err_fit SN1 395.617 737.999 52.617 51.999 -9.708 -8.809 -8.849 0 0.009 ****************************************************** sn2004gt SN 2000cf Original image Residual image PSF used for the fit ecsn (package of SNOOPY) Cappellaro & Patat – Ledan software

  5. Template subtraction Not isolated object Faint object Scientific image, Scientific image without object, tool to make difference image, PSF, aperture correction When we use template subtraction ? SN1997ab HII region SN1997ab HII region ? SN1997ab 01-02-1998 12-12-1999 (filter R) 12-12-1999 (filter B)

  6. Result Host Galaxy SN1997ab 15-03-2004 Ekar SN1997ab 28-12-1999 Danish • Aperture photometry • Photometry with PSF fitting • Geometric Transformation • To be compare the PSF of the two images • To be compare the Flux scale of the two images difference image

  7. Subtraction with ISIS (or DIA) ISIS C. Alard http://www2.iap.fr/users/alard/package.html DIA P.R. Wozniak http://www.astro.princeton.edu/~wozniak/dia/ Ref = Reference Image (best seeing) Im = Program Image Ker = Kernel image (to be found) …the flux scaling factor is the sum of the local kernel …(C. Alard, 2000) …the result is on the scale of the program image. I divide it by the norm of the kernel and express the flux in the units of the reference image…(P. Wozniak, private communication) …the result is on the scale of the program image. I divide it by the norm of the kernel and express the flux in the units of the reference image…(P. Wozniak, private communication) …the result is on the scale of the program image. I divide it by the norm of the kernel and express the flux in the units of the reference image…(P. Wozniak, private communication) (C. Alard 2000; P.R. Wozniak 2001)

  8. Program image Reference image Subtraction between two images ISIS or DIA • Difference image (best seeing) • Geometric scale Scale the list of program images to the reference one • PSF • Flux Scale The difference images have the PSF of the program images • Flux Scale • Flux Scale

  9. Template (image without SN) Subtraction between two images for SNe with SVSUB • Difference image • Geometric scale (immatch) • PSF (daophot) • Make difference mrjphot (ISIS) • Photometry (daophot) • Artificial stars experiment I • Artificial stars experiment II • Target (image with SN) • Reference • (best seeing) Flux Scale PSF Photometry on difference image Error of subtraction • Target (image with SN) PSF Photometry on difference image Error of subtraction • Template • (image without SN) • Reference • (best seeing) ? FSF ?

  10. Template (image without SN) Working in progress [mrjphot aga(DIA)] • Difference image • Geometric scale (immatch) • PSF (daophot) • Make difference mrjphot (ISIS) • Photometry (daophot) • Artificial stars experiment I • Artificial stars experiment II Flux Scale • Target (image with SN) • Reference PSF Photometry on difference image Error of subtraction • Target (image with SN) PSF Photometry on difference image • Template (image without SN) • Reference Error of subtraction FSF It’s possible to select witch star use to make difference We know the FSF

  11. Scaling Factor for images of one telescope B FSF FSF

  12. Scaling Factor for difference telescope HG B FSF FSF FSF In the subtraction between two images we lose the information about the color term

  13. Little Example SN2001ge SN2001gf SN2001ge SN2001gf

  14. Geometric scale 14-02-2000 Danish 15-03-2004 Ekar 1.82m Geomap: Compute geometric transforms using coordinate lists (cl.images.immatch) Gregister: Register 1-D or 2-D images using the geomap transforms (cl.images.immatch) 15-03-2004 Ekar 1.82m after Geometric scale Target Template 14-02-2000 Danish 15-03-2004 Ekar 1.82m ISIS (C. Alard 2000) & DIA (P.R. Wozniak 2000) : use the same technique without find stars manually. • Time • PSF of the two images (noao.digiphot.daophot.psf) • Photometry of sequence stars (noao.digiphot.daophot.allstar)

  15. mrjphot (ISIS) PARAMETERS nstamps_x 9 /*** Number of stamps along X axis ***/ nstamps_y 9 /*** Number of stamps along Y axis***/ sub_x 1 /*** Number of sub_division of the image along X axis ***/ sub_y 1 /*** Number of sub_division of the image along Y axis ***/ half_mesh_size 10 /*** Half kernel size ***/ half_stamp_size 15 /*** Half stamp size ***/ deg_bg 2 /** degree to fit differential bakground variations **/ saturation 60000 /** degree to fit background varaitions **/ pix_min 5. /*** Minimum vaue of the pixels to fit ****/ min_stamp_center 130 /*** Minimum value for object to enter kernel fit *****/ ngauss 3 /*** Number of Gaussians ****/ deg_gauss1 6 /*** Degree associated with 1st Gaussian ****/ deg_gauss2 4 /*** Degree associated with 2nd Gaussian ****/ deg_gauss3 2 /*** Degree associated with 3rd Gaussian ****/ sigma_gauss1 0.7 /*** Sigma of 1st Gaussian ****/ sigma_gauss2 1.5 /*** Sigma of 2nd Gaussian ****/ sigma_gauss3 2.5 /*** Sigma of 3rd Gaussian ****/ deg_spatial 2 /*** Degree of the fit of the spatial variations of the Kernel ****/ sub_x stamp The difference image have the flux scale of the reference

  16. Artificial experiment I Target Target + artif. stars ---------------------------------------------------------- >>> Give position for artificial stars for calibration(> x < then > q <) artificial star magnitude for calibration (-5.): OUTPUT IMAGE: _targart.fits Added Star: 1 - X: 686.00 Y: 201.00 Mag: -5.000 Added Star: 2 - X: 706.00 Y: 255.00 Mag: -5.000 Added Star: 3 - X: 560.00 Y: 274.00 Mag: -5.000 Added Star: 4 - X: 546.00 Y: 277.00 Mag: -5.000 Added Star: 5 - X: 434.00 Y: 148.00 Mag: -5.000 ******************************************************** -4.880 -4.869 -4.888 -4.884 -4.890 -4.886 -4.892 >>> zero point mag difference = 0.12 >>> error = 0.00 ******************************************************** .... min-max rejection .... -4.892 -4.869 -4.8856 0.0038470768111717 5 >>> zero point mag difference = 0.11 >>> error = 0.00 ******************************************************** Difference image addstar (noao.digiphot.daophot.addstar)

  17. Artificial experiment II ---------------------------------------------------------- >>> radius of circle inside of which background is not calculated in unit of FWHM ? (3.): >>> half-lenght of square to cut in unit of FWHM ? (6): >>> Give position for artificial stars for error estimates(> x < then > q <) zero magnitude difference between target and template (0.1144): artificial star magnitude for error estimate (-1.3158180721099): OUTPUT IMAGE: _targart.fits Added Star: 1 - X: 682.00 Y: 493.00 Mag: -1.430 Added Star: 2 - X: 517.00 Y: 361.00 Mag: -1.430 …. ******************************************************** -1.3538180721099 -1.5208180721099 …. >>> average magnitude = -1.40 >>> error = 0.07 ******************************************************** .... min-max rejection .... -1.3876180721099 0.03703646851414 5 >>> average magnitude = -1.39 >>> error = 0.04 ******************************************************** !!! zero 0.11+/- 0.04, err = 0.04 # id ap_original ap_bgsub fit_mag err_art err_fit # SN_FIT SN1 -1.3734 -1.3984 -1.4302180721099 0.03703646851414 0.059 Target + artif. stars Difference image addstar (noao.digiphot.daophot.addstar)

  18. Subtraction with ISIS (or DIA) Ref = Reference Image (best seeing) Im = Program Image Ker = Kernel image (to be found) …the flux scaling factor is the sum of the local kernel …(C. Alard, 2000) …the result is on the scale of the program image. I divide it by the norm of the kernel and express the flux in the units of the reference image…(P. Wozniak, private communication) …the result is on the scale of the program image. I divide it by the norm of the kernel and express the flux in the units of the reference image…(P. Wozniak, private communication) …the result is on the scale of the program image. I divide it by the norm of the kernel and express the flux in the units of the reference image…(P. Wozniak, private communication) (C. Alard 2000; P.R. Wozniak 2001) ISIS http://www2.iap.fr/users/alard/package.html DIA http://www.astro.princeton.edu/~wozniak/dia/

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