Measuring the Growth Factor via Gravitational Lensing
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Transcript Measuring the Growth Factor via Gravitational Lensing
(More) Cosmological
Tests from COSMOS
Lensing
in 2009-2010:
- photo-zs have improved
dramatically
- images/psf now corrected for
CTE
- new shear calibration
underway
+ updated group catalog(s)
so expect stronger signal around peaks
in lensing map, and cleaner dependence
on source and lens redshift
time for some 2nd generation tests of
the lensing signal
Measuring Geometry: Shear Ratio Test
(Jain & Taylor 2003, Bernstein & Jain 2004, Taylor et al. 2007)
Take ratio of shear of objects behind a particular cluster, as a function of
redshift
Details of mass distribution & overall calibration cancel clean
geometric test
Can extend this to continuous result by fitting to all redshifts Z(z)
DLS/DS
Relative
Lensing
Strength
Z(z)
Your cluster goes here
Bartelmann & Schneider 1999
To get a well-defined lens redshift, try looking
behind clusters
Use strength of signal behind cluster as a function of redshift to measure
DA(z):
weak but distinctive signal; relative change (change in distance ratio) is
only 0.5%
Base:
Lens at z = 0.2
h = 0.73, m = 0.27
( or X = 1 - m)
Variants (different curves):
m = 0.25,0.30,0.32
w0 = -1,-0.95,-0.9,-0.85,-0.8
w(z) = w0 + wa(1-a)
with w0 = -1, wa = 0.05, 0.1
h = 0.7, 0.75
0.5% relative change
To get a well-defined lens redshift, try looking
behind clusters
Use strength of signal behind cluster as a function of redshift to measure DA(z):
weak but distinctive signal; relative change (change in distance ratio) is only 0.5%
Lens at z = 0.5
Base:
h = 0.73, m = 0.27
( or X = 1 - m)
Variants (different curves):
m = 0.25,0.30,0.32
w0 = -1,-0.95,-0.9,-0.85,-0.8
w(z) = w0 + wa(1-a)
with w0 = -1, wa = 0.05, 0.1
h = 0.7, 0.75
0.5% relative change
How to stack clusters?
Tangential shear goes as:
so redshift dependence enters via critical surface density:
Thus if we define
and
then
independent of cosmology
(assumes flat models)
Try this behind COSMOS Groups and Clusters
(X-ray
derived
Mass)
Log(volume)
(plot from Leauthaud et al. 2009)
Try this behind COSMOS Groups and Clusters
~67 in top
14 objects?
(X-ray
derived
Mass)
Log(volume)
(plot from Leauthaud et al. 2009)
Try this behind COSMOS Groups and Clusters
could get
another
~60
from less
massive groups?
(X-ray
derived
Mass)
Log(volume)
(plot from Leauthaud et al. 2009)
We see the signal!
Stack of regions within 6’
of
~200+ x-ray groups
good fit in front of/behind
cluster
significance still unclear;
seems less than
expected
effect of other structures
along the line of sight
decreases chi2, but hard
to quantify
Local Dwarfs in Cosmos
A surprising number of nearby galaxies show up in the COSMOS field
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Local Dwarfs in Cosmos
A surprising number of nearby galaxies show up in the COSMOS field
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Local Dwarfs in Cosmos
A surprising number of nearby galaxies show up in the COSMOS field
Local Dwarfs in Cosmos
plus lots of other weird LSB stuff…
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Local Dwarfs in Cosmos
All booming away in the FUV, NUV…
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Local Dwarfs in Cosmos
Where could these be?
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Local Dwarfs in Cosmos
Where could these be?
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Local Dwarfs in Cosmos
Where could these be?
Leo I: 10 Mpc dist., mu ~25
3.3 Mpc away in projection
Leo II: 20 Mpc dist., mu =30.5
1.74 Mpc away in projection
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
NB: if in LEO II, Implies ~120 galaxies in group
Qu i c k T i m e ™ a n d a
T I F F (Un c o m p re s s e d ) d e c o m p re s s o r
a re n e e d e d t o s e e th i s p i c t u re .