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## PowerPoint Slideshow about ' (More) Cosmological Tests from COSMOS Lensing' - basil-brennan

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### (More) Cosmological Tests from COSMOS Lensing

### Measuring Geometry: Shear Ratio Test (Jain & Taylor 2003, Bernstein & Jain 2004, Taylor et al. 2007)

### To get a well-defined lens redshift, try looking behind clusters

### To get a well-defined lens redshift, try looking behind clusters

### Try this behind COSMOS Groups and Clusters

### Try this behind COSMOS Groups and Clusters

### Try this behind COSMOS Groups and Clusters

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

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

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

Use strength of signal behind cluster as a function of redshift to measure DA(z):

weak but distinctive signal; relativechange (change in distance ratio)is only 0.5%

0.5% relative change

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

Use strength of signal behind cluster as a function of redshift to measure DA(z):

weak but distinctive signal; relativechange (change in distance ratio)is only 0.5%

0.5% relative change

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

(X-ray

derived

Mass)

Log(volume)

(plot from Leauthaud et al. 2009)

14 objects?

(X-ray

derived

Mass)

Log(volume)

(plot from Leauthaud et al. 2009)

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

Local Dwarfs in Cosmos

A surprising number of nearby galaxies show up in the COSMOS field

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…

Local Dwarfs in Cosmos

All booming away in the FUV, NUV…

Local Dwarfs in Cosmos

Where could these be?

Local Dwarfs in Cosmos

Where could these be?

Local Dwarfs in Cosmos

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

Where could these be?

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

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