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Lensing of supernovae by galaxies and galaxy clusters
Edvard Mörtsell, Stockholm
Jakob Jönsson, Oxford
Ariel Goobar; Teresa Riehm, Stockholm
Edvard Mörtsell, Stockholm University
Outline
• Lensing of supernovae by galaxies
• Lensing of supernovae by galaxy clusters
Edvard Mörtsell, Stockholm University
Davis, EM et al (2007)
SN = Type Ia supernova = SN Ia
Supernova cosmology
Edvard Mörtsell, Stockholm University
Davis, EM et al (2007)
Distance modulus = m – m(empty universe)
Edvard Mörtsell, Stockholm University
Magnitude uncertainties
• Evolution (0.15 mag)
• Intrinsic dispersion (0.15 mag): Gaussian
• Dust (0.15 mag): Increases with redshift
• Gravitational lensing (0.15 mag)– Increases with redshift– Averages out– Can be corrected for
• We need to get down to 0.015 mag
Edvard Mörtsell, Stockholm University
Correcting for lensing
Credit: Riess, STScI
SN 1997ff: The most distant Type Ia supernova at z = 1.755
Relate dark matter to luminous matter:
Estimated magnification: 0.15 mag
Edvard Mörtsell, Stockholm University
Uncertainties in lensing estimates
• Magnitude limit
• Finite field size
• Redshift and position uncertainties
• Luminous matter to dark matter:– Faber-Jackson and Tully-Fisher relations– Dark matter halo profile and extent
Luminous matter
Edvard Mörtsell, Stockholm University
Lensing vs Hubble residuals Jönsson et al (2006)
Tentative detection (90 % CL) of correlation
Edvard Mörtsell, Stockholm University
Impact on cosmological fits
• Corrections can decrease the scatter from gravitational lensing by a factor of a few
• The bias introduced is negligible [Jönsson et al (2008)]
• Cosmological constraints from supernovae can be improved by 5-10 %
Edvard Mörtsell, Stockholm University
Supernovae and halo masses
Correct masses (circles)
Underestimated masses (squares)
Overestimated masses(triangles)
The slope can be used to estimate masseswith 50 % accuracy using 450 SN Ia (SNLS)
Edvard Mörtsell, Stockholm University
Supernovae and galaxy clusters
• Clusters as telescopes
• Explore supernova rates at high redshifts
• Increase leverage of Hubble diagram
• Possibility to measure time delay and absolute magnification
Edvard Mörtsell, Stockholm University
Pilot study
• Near-IR observations ISAAC/VLT (PI: Ariel Goobar)
• SZ and J-band matching archival data
• A1689, A1835, AC114 monitored in spring of 2007
• Magnitude limit SZ < 24 mag (Vega)
• Average magnification in ISAAC field:– A1689: -3 mag– A1835: -1,5 mag– AC114: -1 mag
Edvard Mörtsell, Stockholm University
A transient candidate
A1689 archival ISAAC and FORS2 data
Goobar et al (2008)
Type IIp at z = 0.68 magnified > 2 mag
!!!Preliminary!!!
Edvard Mörtsell, Stockholm University
Summary and outlook
• Galaxy lenses harmless for SN Ia cosmology
• SN Ia potentially useful as probes of halo masses
• A successful pilot study looking for supernovae behind cluster telescopes
• Further observation using HAWK-I camera will help constraining supernova rates, dark matter distribution, Hubble constant, dark energy properties…