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

Riess et al (2001)

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

More supernovae in GOODS fields

Jönsson et al (2006)

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

Davis, EM et al (2007)

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

Goobar et al (2008)

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

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…