more cosmological tests from cosmos lensing
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(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)

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more cosmological tests from cosmos 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

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

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

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

to get a well defined lens redshift try looking behind clusters1

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

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
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

try this behind cosmos groups and clusters

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 clusters1

~67  in top

14 objects?

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 clusters2

could get

another

~60 

from less

massive groups?

Try this behind COSMOS Groups and Clusters

(X-ray

derived

Mass)

Log(volume)

(plot from Leauthaud et al. 2009)

we see the signal
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
Local Dwarfs in Cosmos

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

local dwarfs in cosmos1
Local Dwarfs in Cosmos

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

local dwarfs in cosmos2
Local Dwarfs in Cosmos

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

local dwarfs in cosmos3
Local Dwarfs in Cosmos

plus lots of other weird LSB stuff…

local dwarfs in cosmos4
Local Dwarfs in Cosmos

All booming away in the FUV, NUV…

local dwarfs in cosmos5
Local Dwarfs in Cosmos

Where could these be?

local dwarfs in cosmos6
Local Dwarfs in Cosmos

Where could these be?

local dwarfs in cosmos7
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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