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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) - PowerPoint PPT Presentation
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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)
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Bartelmann & Schneider 1999
Relative Lensing Strength Z(z)
Your cluster goes here
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
To get a well-defined lens redshift, try looking behind clustersUse 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 = 0.2
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
To get a well-defined lens redshift, try looking behind clustersUse 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, 0.750.5% 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
Log(volume)
Try this behind COSMOS Groups and Clusters
(plot from Leauthaud et al. 2009)
(X-ray derived Mass)
Log(volume)
Try this behind COSMOS Groups and Clusters
(plot from Leauthaud et al. 2009)
(X-ray derived Mass)
~67 in top 14 objects?
Log(volume)
Try this behind COSMOS Groups and Clusters
(plot from Leauthaud et al. 2009)
(X-ray derived Mass)
could get another~60 from less massive groups?
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 CosmosA surprising number of nearby galaxies show up in the COSMOS field
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Local Dwarfs in CosmosA surprising number of nearby galaxies show up in the COSMOS field
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Local Dwarfs in CosmosA surprising number of nearby galaxies show up in the COSMOS field
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Local Dwarfs in Cosmosplus lots of other weird LSB stuff…
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Local Dwarfs in CosmosAll booming away in the FUV, NUV…
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Local Dwarfs in CosmosWhere could these be?
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Local Dwarfs in CosmosWhere could these be?
Local Dwarfs in CosmosWhere could these be?
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Leo I: 10 Mpc dist., mu ~253.3 Mpc away in projection
Leo II: 20 Mpc dist., mu =30.51.74 Mpc away in projection
NB: if in LEO II, Implies ~120 galaxies in group