photometry with technique of template subtraction: personal experience. stefano valenti physics...
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Photometry with technique of Template Subtraction: personal experience.
Stefano ValentiPhysics Department of Ferrara – INAF Astronomical Observatory of Capodimonte
Padova-Asiago Supernova Group (http://web.pd.astro.it/supern/)
Other techniques
Aperture Photometry Isolated object
Photometry with PSF Fitting Not isolated object
measure the PSF Fit the object with the PSF
sn2004gt
Mark A
PSF
PSF (noao.digiphot.daophot.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_R9 stars read from temp_SN97ab_281299_R.mag
Star 1 rejected by userStar 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.fitsWriting output PSF star list temp_SN97ab_281299_R.pstWriting output PSF star group file temp_SN97ab_281299_R.psg
ecpsf (package of SNOOPY) Cappellaro & Patat – Ledan software
allstar (noao.digiphot.daophot.allstar)
PSF, Magnitude of field stars, Aperture correction
sn2004gt
PSF PHOTOMETRY OF SN
ecsn (package of SNOOPY) Cappellaro & Patat – Ledan software
allstar (noao.digiphot.daophot.allstar)
Original image Residual image
PSF used for the fitDifference image
PSF used for the fit
Residual image
SN 2000cf
>>> 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
******************************************************
When we use template subtraction ?
Template subtraction Not isolated object Faint object
Scientific image, Scientific image without object, tool to make difference image, PSF, aperture correction
01-02-1998 12-12-1999 (filter R) 12-12-1999 (filter B)
SN1997ab
SN1997ab
HII regionSN1997ab
HII region
?
Result
SN1997ab 28-12-1999 Danish
Host Galaxy SN1997ab15-03-2004 Ekar
difference image
•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
Subtraction with ISIS (or DIA)
n
nn v,uK)y,x(ay,x;v,uKer
ji/vun vuev,uK k
222 2
k,j,in
Ref = Reference Image (best seeing)Im = Program Image Ker = Kernel image (to be found)
j,i
jij,in yxby,xa
(C. Alard 2000; P.R. Wozniak 2001)
…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)
ISIS C. Alard http://www2.iap.fr/users/alard/package.html
DIA P.R. Wozniak http://www.astro.princeton.edu/~wozniak/dia/
)y,x(Diffy,x;v,uKer)v,u(fRey,xIm
Subtraction between two images ISIS or DIA
Program image Reference image
Geometric scaleScale the list of program images to the reference one
PSF
Flux Scale Flux Scale
Difference image
The difference images have the PSF of the program images
Flux Scale
(best seeing)
Subtraction between two images for SNe with SVSUB
Template
(image without SN)
Artificial stars experiment I
Difference imageGeometric scale
(immatch)
Target (image
with SN) Template
(image without SN)
Reference
(best seeing)
Target (image
with SN)
Reference
(best seeing)
FSF
PSF (daophot)
Make difference mrjphot (ISIS)Flux Scale
Artificial stars experiment II
Error of subtraction
Error of subtraction
Photometry (daophot)
PSF Photometry on difference image
PSF Photometry on difference image
?
?
Working in progress [mrjphot aga(DIA)]
Template
(image without SN)
Difference image
Target
(image with SN) Template
(image without SN)Reference
Target
(image with SN)Reference
We know the FSFIt’s possible to select witch star use to make difference
Artificial stars experiment I
Geometric scale
(immatch)
FSF
PSF (daophot)
Make difference mrjphot (ISIS)Flux Scale
Artificial stars experiment II
Error of subtraction
Error of subtraction
Photometry (daophot)
PSF Photometry on difference image
PSF Photometry on difference image
Scaling Factor for images of one telescope
FSF
FSF
B
Scaling Factor for difference telescope
FSFFSF
FSF
HG
In the subtraction between two images we lose the information about the color term
B
Little Example SN2001ge
SN2001gf
SN2001gf SN2001ge
Geometric scale14-02-2000 Danish
15-03-2004 Ekar 1.82m14-02-2000 Danish
15-03-2004 Ekar 1.82m
15-03-2004 Ekar 1.82m after Geometric scale
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)
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)
Target Template
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 ****/
stampsub_x
The difference image have the flux scale of the reference
)y,x(Diffy,x;v,uKer)v,u(fRey,xIm
Artificial experiment I
---------------------------------------------------------->>> 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
Target + artif. starsTarget
addstar (noao.digiphot.daophot.addstar)
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)
Subtraction with ISIS (or DIA)
iiiii y,x;v,uKer)v,u(fRey,xIm 2
n
nn v,uK)y,x(ay,x;v,uKer
ji/vun vuev,uK k
222 2
k,j,in
Ref = Reference Image (best seeing)Im = Program Image Ker = Kernel image (to be found)
j,i
jij,in yxby,xa
(C. Alard 2000; P.R. Wozniak 2001)
…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)
ISIS http://www2.iap.fr/users/alard/package.html
DIA http://www.astro.princeton.edu/~wozniak/dia/