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P. Astier Euclid-France(2013) 1 The brighter-fatter effect and pixel correlations Pierre Antilogus, Pierre Astier, Augustin Guyonnet, Nicolas Regnault LPNHE / IN2P3 / CNRS , Universités Paris 6&7.

The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

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Page 1: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

1

Th

e b

rig

hte

r-fa

tter

effe

ctan

d p

ixel

co

rrel

atio

ns

Pie

rre

An

tilo

gu

s, P

ierr

e A

stie

r,

Au

gust

in G

uyo

nn

et, N

icola

s R

egna

ult

LP

NH

E /

IN

2P

3/

CN

RS

, U

niv

ersi

tés

Pa

ris

6&

7.

Page 2: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

2

Th

e b

rig

hte

r-fa

tter

eff

ect

(1)

-M

easu

rem

ents

by

P. D

oher

ty(H

arvar

d)

In t

he

lab

ora

tory

.

-”L

ab s

pots

”C

CD

E2V

(L

SS

T)

-In

tensi

ty i

s var

ied

via

inte

gra

tion

tim

e.

Mea

sure

sec

ond m

om

ents

.

Page 3: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

3

Th

e b

rig

hte

r-fa

tter

eff

ect

(2)

Bri

ght

spo

ts a

re b

road

erth

anfa

int

ones

, b

y a

sm

all

amo

unt.

-M

easu

rem

ents

by

P. D

oher

ty (

Har

var

d)

Inth

e la

bora

tory

.

-”L

absp

ots

”C

CD

E2V

(L

SS

T)

-In

tensi

ty i

s var

ied

via

inte

gra

tion t

ime.

-ty

pic

ally

a 2

-3%

in

crea

se o

ver

the

full

dynam

ic r

ange.

Page 4: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

4

Th

e ef

fect

als

osh

ow

s up

on

Meg

aCam

(@

CF

HT

)...

An

d i

t is

pre

tty

mu

chac

hro

mat

ic(S

NL

S p

hoto

met

ryte

chnic

al p

aper

, A

&A

557, A

.55 2

013 )L

ess

than

0.5

%over

the

wh

ole

ra

ng

e.

Chip

s :

E2V

CC

D42

-90

(thin

ned

chip

s)

(CF

HT

LS

dat

a)

Page 5: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

id-F

rance

(201

3)

5

…an

d o

n D

EC

am (

@C

TIO

-4m

)

Mea

sure

men

ts f

rom

Sci

ence

Ver

ific

atio

nD

ata

(i.e

. on s

ky)

wit

ha

tiny

colo

r co

rrec

tion

1 t

o 2

%.

LB

L/D

AL

SA

chip

shig

h-r

ho

250 µ

m t

hic

k

r ban

d

Page 6: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

6

Hy

per

Su

pri

me

Cam

Fro

mR

. L

upto

n.

Page 7: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

7

Th

e b

righ

ter-

fatt

er e

ffec

t

●T

he

sou

rce

of

the

effe

cth

asto

be

no

n-l

inea

r.

–If

it w

her

e li

nea

r, s

hap

e w

ou

ldn

ot

chan

ge

wit

h

flu

x.

–It

hen

ce c

annot

be

due

to d

iffu

sion

.

●N

on

-lin

eari

tyof

ov

eral

l re

spo

nse

?

–O

bvio

usl

y p

oss

ible

–L

inea

r w

ith

flu

x?

Page 8: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

8

Oth

er s

tran

ge

effe

cts

on

CC

Ds

(1)

Var

ian

ce o

f fl

atfi

eld

s is

not

exac

tly

pro

port

ion

al t

o t

hei

r av

erag

e

??

No

n-l

inea

rity

of

PT

Cte

nds

to g

od

ow

n

wh

en r

e-b

innin

g

the

imag

e.

Pho

ton T

ransf

er C

urv

e (P

TC

) :

var

iance

=f(

aver

age)

Sim

éon D

enis

Po

isso

n

CC

D E

2V

250

Page 9: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

9

Oth

er s

tran

ge

effe

cts

on

CC

Ds

(2)

Fla

t-fi

eld

pix

els

are

no

tst

atis

tica

lly

in

dep

end

ent.

Thei

rco

rrel

atio

ns

incr

ease

(li

nea

rly

) w

ith

illu

min

atio

n.

-L

inea

rin

crea

se w

ith

flat

-fie

ldav

erag

e-

Dep

ends

on

som

e el

ectr

ost

atic

boun

dar

yco

ndit

ion.

- E

2V

CC

D

-Mea

sure

men

tsby P

.Doher

ty(H

arvar

d)

-An

aly

sis

by

A. G

uyonnet

(Par

is)

Nea

rest

ver

tica

lnei

ghbors

Cov

/Var

Aver

age

Page 10: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

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3)

10

Th

ese

corr

elat

ion

s in

fla

t fi

elds

seem

to

be

achro

mat

ic

So, th

e ef

fect

does

no

t dep

end o

nh

ow

dee

p p

hoto

ns

conver

t.

Page 11: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

11

Th

ese

flat

fiel

d c

orr

elat

ions

dec

ay w

ith

dis

tance

- co

rrel

atio

ns

dec

reas

ero

ughly

exponen

tial

lyw

ith s

epar

atio

n.

- T

hey

are

larg

er a

long

Y t

han

alo

ng X

.

Page 12: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

12

No

n-l

inea

r P

TC

an

d c

orr

elat

ion

s

Unsu

rpri

singly

, w

hen

acc

ounti

ng f

or

pix

el c

orr

elat

ions,

the

PT

C b

ecom

esm

ore

lin

ear

PT

C f

or

ccd e

2v 2

50

Page 13: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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ucl

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13

So,

We

det

ect

3 e

ffec

ts :

●bri

ghte

r-fa

tter

for

star

s/sp

ots

●V

aria

nce

of

flat

fiel

ds

is s

mal

ler

than

Pois

son

●F

latf

ield

s ex

hib

it c

orr

elat

ions

Lin

earl

y i

ncr

easi

ng w

ith i

llum

inat

ion.

-T

he

two l

ast

effe

cts

are

triv

iall

y r

elat

ed.

-S

mo

oth

ing o

f fl

atfi

elds

and

star

s m

ight

shar

e th

e sa

me

ori

gin

.

All

3 e

ffec

tsre

qu

ire

som

e n

on

-lin

ear

mec

han

ism

Page 14: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

14

Co

ulo

mb

forc

es i

n a

CC

D Em

pty

CC

D

Page 15: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

15

Co

ulo

mb

forc

es i

n a

CC

D

50

ke

Page 16: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

id-F

rance

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3)

16

50

ke

Dep

endin

g o

n t

he

store

dch

arge,

ele

ctro

ns

dri

ftin

g

her

eg

ole

ft o

r ri

ght

Page 17: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

17

Em

pty

CC

DT

op v

iew

Page 18: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

18

Add a

bri

ght

star

Top v

iew

Page 19: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

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3)

19

Sh

ifte

d p

ixel

boundar

ies

(shif

ts x

5)

Top v

iew

Page 20: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

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3)

20

So,

Du

e to

Co

ulo

mb f

orc

es,

ov

erfi

lled

pix

els

get

smal

ler

w.r

.tth

eav

erag

ep

ixel

si

ze.

Th

is e

ffec

t:

Char

les-

August

inde

Coulo

mb

●R

edu

ces

spat

ial

var

iance

of

flat

-fie

lds

w.r

.t P

ois

son

●C

ause

spo

siti

ve

corr

elat

ion

s in

fla

t fi

eld

s (s

ou

rced

by

Po

isso

nfl

uct

uat

ions)

●B

road

ens

bri

gh

t sp

ots

w.r

.t f

ainte

r on

es

Page 21: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

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3)

21

Can

Co

ulo

mb

fo

rces

cau

se t

he

obse

rved

size

of

effe

cts

?

A s

ket

chy s

imula

tion

roughly

rep

roduce

s th

esi

ze o

f th

e obse

rved

co

rrel

atio

ns

and

of

the

bri

ghte

r-fa

tter

sl

ope.

E2V

CC

D

Page 22: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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3)

22An e

mp

iric

al m

od

el

●W

edo

no

t k

no

w t

he

det

ails

of

ho

w C

CD

s ar

em

ade

●M

ost

ven

do

rs w

ould

no

t an

swer

ou

r q

ues

tio

ns.

●T

he

effe

ctis

smal

l an

dh

ence

Tay

lor

exp

ansi

ons

shou

ld h

old

●R

ath

erth

anm

akin

gqu

anti

tati

ve

pre

dic

tio

ns

fro

mel

ectr

ost

atic

s, w

e m

ake

a g

ener

al f

irst

ord

er

mod

el a

nd

(tr

y t

o)

der

ive

its

un

kn

ow

ns

from

dat

a.

Page 23: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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ucl

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23A s

imp

list

ic m

odel

-C

har

ges

sto

red

in

a C

CD

sou

rce

an e

lect

ric

fiel

d-

Dri

ft t

raje

cto

ries

are

per

turb

ed b

y t

his

add

itio

nal

ele

ctri

c fi

eld

-P

ixel

sb

oun

dar

ies

are

affe

cted

by

thes

e per

turb

atio

ns.

→ E

ffec

tive

pix

elb

oun

dar

ies

are

(mar

gin

ally

)d

yn

amic

al

(0,0

)

(0,1

)

Qij

(1,0

)

(0,1

)

(0,-

1)

(-1

,0)

Page 24: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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24

(0,0

)

(0,1

)

Qij

(1,0

)

(0,1

)

(0,-

1)

(-1,0

)

Boundar

y s

hif

t, t

o f

irst

ord

er i

nso

urc

e ch

arges

:

Char

ge

“tra

nsf

er”

(induce

d b

y a

ll Q

ij):

Sum

over

the

4 s

ides

Page 25: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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25

Th

is i

s a

no

n-l

inea

ref

fect

Sourc

e ch

arge

Tes

t ch

arge.

Ass

um

es t

he

imag

eis

wel

l sa

mple

d.

To b

e det

erm

ined

:●

Inte

gra

tes

all

nu

mer

ical

fact

ors

fro

m t

he

pre

vio

us

slid

e●

Char

acte

rist

ic o

f a

dev

ice

(+ o

per

atin

g c

ondit

ion

s)

Char

ge

shu

ffli

ng

: no

char

ge

get

s lo

st

Page 26: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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26Co

rrel

atio

ns

in f

lats

For

a fl

at-f

ield

(av

erag

eµ,

var

ian

ce V

)on

eget

s :

Sum

over

4 s

ides

So :

- co

rrel

atio

ns

(Cov/V

) in

crea

seli

nea

rly w

ith i

llum

inat

ion

- var

iance

of

flat

-fie

lds

: P

ois

son t

erm

min

us

a quad

rati

c co

rrec

tion

Page 27: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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27

Do

th

e b

rig

hte

r-fa

tter

eff

ect

and

fla

t-fi

eld

corr

elat

ion

s sh

are

the

sam

e o

rig

in ?

TE

ST

:

Der

ive

coef

fici

ents

from

fla

t-fi

eld

corr

elat

ions

Scr

amb

lefa

int

spots

(or

star

s) a

nd c

om

par

eto

bri

ght

ones

Page 28: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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28

Fro

m c

orr

elat

ion

s to

co

effi

cien

ts.

(0,0

)

(0,1

)

Qij

(1,0

)

(0,1

)

(0,-

1)

(-1

,0)

At

“lar

ge”

dis

tance

, co

rrel

atio

ns

var

y m

ost

lyas

the

der

ivat

ive

of

the

boundar

y d

ispla

cem

ent

wit

h p

osi

tio

n.

Page 29: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

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29

Get

tin

g t

he

“a”

coef

fici

ents

fro

m f

lat-

fiel

ds

(1)

●If

one

wan

ts t

o m

easu

re t

he

“a”

coef

fici

ents

up t

o s

epar

atio

n o

f n p

ixel

s,th

ere

are

~4 n

2

such

coef

fici

ents

.

●W

ith s

ym

met

ries

,it

dro

ps

to ~

2n

2

●T

her

e ar

e only

~n

2 c

orr

elat

ions

to b

e m

easu

red

●W

ehen

ce h

ave

to c

ook-u

p ~

n2 c

onst

rain

ts.

Page 30: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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30

Get

tin

g t

he

“a”

coef

fici

ents

fro

m f

lat-

fiel

ds

(2)

●Im

po

se r

atio

s o

f co

effi

cien

ts a

t si

mil

ar d

ista

nce

su

sin

g t

he

ov

eral

l sh

ape

of

the

dec

ay.

●R

esu

lts

are

reas

onab

ly i

ndep

end

ent

of

the

use

dan

aly

tica

l sh

ape.

●A

ny

bet

ter

sug

ges

tio

n ?

Page 31: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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3)

31

- P

redic

ted b

righte

r-fa

tter

slo

pes

are

~20%

larg

er t

han

m

easu

rem

ents

.-

consi

sten

tly f

or

both

x a

nd y

and

55

0an

d 9

00 n

m

Ap

ply

ing

the

“a”

coef

fici

ents

(L

SS

T/E

2V

)

MC

pro

pag

atio

no

fco

rrel

atio

n m

easu

rem

ent

unce

rtai

nti

es

900 n

m

550 n

m

Sca

le u

pfa

int

spots

and s

cram

ble

them

.

Page 32: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

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3)

32

DE

Cam

Pre

dic

tion

Fro

m c

orr

elat

ion

s

Ap

ply

ing

the

“a”

coef

fici

ents

“Sim

ula

tions”

her

e pro

ceed

from

the

(flu

x-i

ndep

enden

t)

PS

F.

Only

CC

D1

7.

The

com

par

ison

is l

imit

ed b

y s

tati

stic

sof

flat

fiel

ds

and s

tars

.

Page 33: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

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rance

(201

3)

33

DE

Cam

:al

l ch

ips

Ap

ply

ing

th

e “a

” co

effi

cien

ts

Pre

dic

ted

fro

mco

rrel

atio

ns

Pre

dic

ted

fro

m c

orr

elat

ion

s

●T

he

mea

sure

d b

righte

r-fa

tter

slo

pes

see

mm

argin

ally

com

pat

ible

bet

wee

n c

hip

s●

The

corr

elat

ions

seem

com

pat

ible

, but

the

stat

isti

cs i

s lo

w t

hough.

Agre

emen

tat

the

15-2

0%

level

Page 34: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

id-F

rance

(201

3)

34

DE

Cam

: n

on

-lin

eari

ty o

fre

spo

nse

●D

EC

amis

susp

ecte

d t

o e

xhib

it n

on-l

inea

riti

es o

f re

sponse

(se

e G

ary's

tal

k)

●T

his

contr

ibu

tes

to t

he

bri

ghte

r-fa

tter

eff

ect.

●W

ith t

he

non-l

inea

r co

rrec

tions,

the

obse

rved

bri

ghte

r-fa

tter

eff

ect

incr

ease

sb

y~

60 %

.P

red

icte

dfr

om

corr

elat

ion

sP

red

icte

d

fro

m c

orr

elat

ion

s

Shif

t due

tono

n-l

inea

rity

co

rrec

tion

Xy

DE

Cam

non-l

inea

rity

: h

ttps:

//cd

cvs.

fnal

.gov/r

edm

ine/

pro

ject

s/des

-sci

-ver

ific

atio

n/w

iki/

AB

_R

atio

_V

aria

tion

Page 35: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

id-F

rance

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3)

35

Ap

ply

ing

the

“a”

coef

fici

ents

: D

EC

am

●A

gre

emen

t b

etw

een

mea

sure

men

tsan

dp

red

icti

on

s fr

om

fla

t-fi

eld

at

the

–~

20

% l

evel

(ign

ori

ng N

L c

orr

ecti

on

s)

–~

30

% l

evel

(w

ith

no

nli

nea

r co

rrec

tions)

●O

ur

mea

sure

men

ts o

f co

rrel

atio

ns

are

stat

isti

csli

mit

ed.

●N

on

-lin

eari

tyof

resp

onse

str

on

gly

aff

ects

th

e o

bse

rved

bri

gh

ter-

fatt

er s

lope.

Page 36: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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3)

36

Ap

ply

ing

the

“a”

coef

fici

ents

Meg

acam

(thin

ned

CC

Ds)

Mea

sure

men

t:sl

ope

~ 0

.5

Pre

dic

tion f

rom

fla

t-fi

elds

slope

~ 0

.34 +

/- 0

.15

(mea

sure

d d

ista

nt

corr

elat

ions

are

“in t

he

nois

e”)

Page 37: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

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37

- T

he

“a”

coef

fici

ents

are

sm

all:

- C

orr

ect

for

the

effe

ct b

yap

ply

ing

flip

ped

-sig

n c

oef

fici

ents

at

the

pix

el l

evel

- R

emea

sure

sta

r si

zes

as a

funct

ion o

f fl

ux

Un

scra

mb

ling

: c

orr

ecti

on

at t

he

pix

el l

evel

Unce

rtai

nti

es o

f co

rrel

atio

ns

Page 38: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

stie

r E

ucl

id-F

rance

(201

3)

38Pra

ctic

al d

iffi

cult

ies

●M

easu

rin

g s

mal

l co

rrel

atio

ns

–S

tati

stic

s nee

ded

(10

0 M

pix

to r

each

10

-4)

–B

ewar

e o

f oth

er c

orr

elat

ion

sourc

es (

nee

d a

ram

p)

●N

on

-lin

eari

tyof

resp

onse

co

ntr

ibu

tes

toth

e B

Fef

fect –

No

n-l

inea

rity

dif

ficu

ltto

mea

sure

●M

ore

co

effi

cien

ts t

han

mea

sure

men

ts

–Im

pro

ve

elec

trost

atic

s?

●C

orr

ecti

on

–P

ixel

s le

vel

?

–O

rP

SF

mo

del

?

Page 39: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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r E

ucl

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rance

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3)

39

Dis

tort

ion

s w

ith

ou

t as

sum

ing

go

od

sam

pli

ng

Sourc

e ch

arge

Tes

t ch

arge.

Ass

um

es t

he

imag

eis

wel

l sa

mple

d.

Corr

ecti

on t

o P

SF

mo

del

:

Pix

el l

evel

:

Page 40: The brighter-fattereffect and pixel correlations Pierre ... · P. Astier Euclid-France(2013) The brighter-fatter effect (2) Bright spots are broaderthanfaint ones, by a small amount

P. A

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id-F

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3)

40

Con

clu

sio

ns

●W

e th

ink t

o h

ave

com

pel

ling

evid

ence

th

at t

he

bri

ghte

r-fa

tter

eff

ect

and c

orr

elat

ion

s in

fla

tfi

eld

s sh

are

the

sam

e ori

gin

: th

e C

oulo

mb l

aw.

●C

orr

elat

ions

are

the

key

toco

nst

rain

the

bri

ghte

r-fa

tter

effe

ct.

●N

on-l

inea

rity

of

resp

onse

an

d o

ther

sourc

es o

fco

rrel

atio

ns

mak

e th

e li

nk

tric

ky.

●P

ract

ical

han

dli

ng o

fth

e ef

fect

stil

lto

be

sett

led

.

●H

andli

ng

the

bri

gh

ter-

fatt

er e

ffec

t at

the

~10

%le

vel

is

pro

bab

ly n

ot

too

dif

ficu

lt.

●W

e ar

e not

qu

ite

atu

nder

stan

din

g t

he

slo

pe

atth

e 1%

lev

el.