Download PPT

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/)
Other techniques
Aperture Photometry

Isolated object
Mark A
Photometry with PSF Fitting

Not isolated object
 measure
the PSF
Fit the object with the PSF
sn2004gt
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
PSF (noao.digiphot.daophot.psf)
allstar (noao.digiphot.daophot.allstar)
PSF, Magnitude of field stars,
Aperture correction
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
ecpsf (package of SNOOPY)
Cappellaro & Patat – Ledan software
PSF PHOTOMETRY OF SN
allstar (noao.digiphot.daophot.allstar)
>>> 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
******************************************************
PSF usedimage
for the fit
Difference
Residual image
sn2004gt
SN 2000cf
Original image Residual image
PSF used for the fit
ecsn (package of SNOOPY)
Cappellaro & Patat – Ledan software
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
SN1997ab
HII region
SN1997ab
HII region
?
SN1997ab
01-02-1998
12-12-1999 (filter R)
12-12-1999 (filter B)
Result
SN1997ab
28-12-1999 Danish
Host Galaxy SN1997ab
15-03-2004 Ekar
•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
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/
Im x , y   Re f ( u ,v )  Ker u ,v ; x , y   Diff ( x , y )
Ker u ,v ; x , y    an ( x , y ) Kn u ,v 
n
Ref = Reference Image (best seeing)
Im = Program Image
Ker = Kernel image (to be found)
 u 2 v 2 / 2 k2 i j
K u ,v   e
uv
n
an x , y    bi , j x i y j
n  i , j , k 
i,j
(C. Alard 2000; P.R. Wozniak 2001)
…the flux scaling factor is the sum of
the local kernel …(C. Alard, 2000)
…the result
result is
is on
on the
the scale
scale of
of the
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
image…(P.
communication)
Subtraction between two images ISIS or DIA
Program image
Reference image
(best seeing)
Difference image
Geometric scale
Scale the list of program images
to the reference one
PSF
The difference images have the
PSF of the program images
 Flux
Scale
Flux Scale
Flux Scale
Subtraction between two images for SNe with SVSUB
Difference image
 Geometric  PSF
scale
(immatch)
 Target (image
 Make
 Photometry  Artificial
 Artificial
(daophot) difference (daophot)
stars
stars
mrjphot
experiment I experiment II
(ISIS)
Flux Scale
with SN)
Reference
PSF
Photometry
on difference
image
(best seeing)
 Template
(image without SN)
Error of
subtraction
 Target (image
with SN)
 Template
(image without SN)
?
PSF
Photometry
on difference
image
FSF
Reference
(best seeing)
?
Error of
subtraction
Working in progress [mrjphot
aga(DIA)]
Difference image
 Geometric  PSF
scale
(immatch)
 Make
 Photometry  Artificial
 Artificial
(daophot) difference (daophot)
stars
stars
mrjphot
experiment I experiment II
(ISIS)
Flux Scale
 Target
(image with SN)
Reference
 Template
(image without SN)
PSF
Photometry
on difference
image
Error of
subtraction
 Target
(image with SN)
 Template
(image without SN)
Reference
PSF
Photometry
on difference
image
It’s possible to select witch
star use to make difference
FSF
Error of
subtraction
We know the FSF
Scaling Factor for images of one telescope
B
FSF
FSF
Scaling Factor for difference telescope
HG
B
FSF
FSF
FSF
In the subtraction between two images we lose the information about the color term
Little Example
SN2001ge
SN2001gf
SN2001gf
SN2001ge
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)
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
Im x , y   Re f ( u ,v )  Ker u ,v ; x , y   Diff ( x , y )
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
********************************************************
Target
Target + artif. stars
Difference image
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)
2








Im
x
,
y

Re
f
(
u
,
v
)

Ker
u
,
v
;
x
,
y

i
i
i
i
i
Ker u ,v ; x , y    an ( x , y ) Kn u ,v 
n
Ref = Reference Image (best seeing)
Im = Program Image
Ker = Kernel image (to be found)
Kn u ,v   e 

 u 2 v 2 / 2 k2
u iv j
an x , y    bi , j x i y j n  i , j , k 
i,j
…the flux scaling factor is the sum of
the local kernel …(C. Alard, 2000)
…the result
result is
is on
on the
the scale
scale of
of the
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
image…(P.
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/