Gravitational Lensing
Filipe B. Abdalla
Apparent deflection angle α
• = 4 G M / (c2 b)
• NB. Independent of light wavelength
b
Observer
Dark matter halos
Background sources
 Statistical measure of shear pattern, ~1% distortion
 Radial distances de...
Observer
Dark matter halos
Background sources
 Statistical measure of shear pattern, ~1% distortion
 Radial distances de...
Mass Mapping CFHTLS
Cluster Weak Lensing
• Weak Lensing
measures cluster
masses, which are
needed to use them
as Dark Energy
probes
• Prelimin...
Cosmic shear two point tomography
Cosmic shear two point tomography
Cosmic shear two point tomography
Data from CFHTLS
Three problems with lensing:
for either tomography and cluster mass
measurements:
• Measuring shapes
• Photometric redshif...
Measuring the shear!
Measuring shapes
is hard
Galaxy spectrum at 2 different redshifts,
overlaid on griz and IR bandpasses
• Photometric redshifts
(photo-z’s) are deter...
Hyper-Z: the first photo-z code
• Simple chi squared fit
of fluxes to the data
• Very simple and very
successful
• Has lim...
from DES Test Data in November
High Redshift Cluster Discovered by
DES
Cosmic shear
Additional
contributions
What we
measure
Intrinsic alignements.
Intrinsic-shear correlation (GI)
Hirata&Seljak
High z galaxy gravitationally
sheared tangentially
Dark matter at z1 Net an...
END
Upcoming SlideShare
Loading in …5
×

An Overview of Gravitational Lensing

450 views

Published on

Review talk by Dr Filipe Abdalla at the SuperJEDI Conference, July 2013

Published in: Technology, Spiritual
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
450
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
5
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

An Overview of Gravitational Lensing

  1. 1. Gravitational Lensing Filipe B. Abdalla
  2. 2. Apparent deflection angle α • = 4 G M / (c2 b) • NB. Independent of light wavelength b
  3. 3. Observer Dark matter halos Background sources  Statistical measure of shear pattern, ~1% distortion  Radial distances depend on geometry of Universe  Foreground mass distribution depends on growth of structure Dark matter halos Background sources Dark matter halos Background sources Dark matter halos Observer Background sources Dark matter halos
  4. 4. Observer Dark matter halos Background sources  Statistical measure of shear pattern, ~1% distortion  Radial distances depend on geometry of Universe  Foreground mass distribution depends on growth of structure Dark matter halos Background sources Dark matter halos Background sources Dark matter halos Observer Background sources Dark matter halos
  5. 5. Mass Mapping CFHTLS
  6. 6. Cluster Weak Lensing • Weak Lensing measures cluster masses, which are needed to use them as Dark Energy probes • Preliminary cluster mass map (contours) from DES Weak Lensing
  7. 7. Cosmic shear two point tomography
  8. 8. Cosmic shear two point tomography
  9. 9. Cosmic shear two point tomography
  10. 10. Data from CFHTLS
  11. 11. Three problems with lensing: for either tomography and cluster mass measurements: • Measuring shapes • Photometric redshifts • Intrinsic alignments
  12. 12. Measuring the shear!
  13. 13. Measuring shapes is hard
  14. 14. Galaxy spectrum at 2 different redshifts, overlaid on griz and IR bandpasses • Photometric redshifts (photo-z’s) are determined from the fluxes of galaxies through a set of filters • May be thought of as low-resolution spectroscopy • Photo-z signal comes primarily from strong galaxy spectral features, like the 4000 Å break, as they redshift through the filter bandpasses Photometric Redshifts
  15. 15. Hyper-Z: the first photo-z code • Simple chi squared fit of fluxes to the data • Very simple and very successful • Has limitations: - Degeneracy, flat chi squared - Mis-identification of features - contamination from AGN - are errors reliable? Credit: M. Bolzonella
  16. 16. from DES Test Data in November High Redshift Cluster Discovered by DES
  17. 17. Cosmic shear Additional contributions What we measure Intrinsic alignements.
  18. 18. Intrinsic-shear correlation (GI) Hirata&Seljak High z galaxy gravitationally sheared tangentially Dark matter at z1 Net anti-correlation between galaxy ellipticities with no prefered scale Galaxy at z1 is tidally sheared
  19. 19. END

×