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 .