1. (More) Cosmological Tests from COSMOS Lensing
- 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

2. 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

3. 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:
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
Lens at z = 0.2
0.5% relative change

4. 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:
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
Lens at z = 0.5
0.5% relative change

5. How to stack clusters? Tangential shear goes as:
so redshift dependence enters via critical surface density:
Thus if we define (assumes flat models)
and
then
independent of cosmology

6. Try this behind COSMOS Groups and Clusters
(X-ray
derived
Mass)
Log(volume)
(plot from Leauthaud et al. 2009)

7. Try this behind COSMOS Groups and Clusters
~67  in top
14 objects?
(X-ray
derived
Mass)
Log(volume)
(plot from Leauthaud et al. 2009)

8. 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)

9. 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

10. Local Dwarfs in Cosmos
A surprising number of nearby galaxies show up in the COSMOS field 

11. Local Dwarfs in Cosmos
A surprising number of nearby galaxies show up in the COSMOS field 

12. Local Dwarfs in Cosmos
A surprising number of nearby galaxies show up in the COSMOS field 

13. Local Dwarfs in Cosmos
plus lots of other weird LSB stuff… 

14. Local Dwarfs in Cosmos
All booming away in the FUV, NUV… 

15. Local Dwarfs in Cosmos
Where could these be? 

16. Local Dwarfs in Cosmos
Where could these be? 

17. 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 
NB: if in LEO II, Implies ~120 galaxies in group