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Peculiar Velocities in Supernova Cosmology
Bryony MartinMSc, Department of Astronomy, University of Cape Town
Supervised by: Dr Kurt van der Heyden & Prof Bruce Bassett
SKA SA Postgraduate Bursary Conference, November 2011
Kessler, et al. 2009
Peculiar Velocities in Supernova Cosmology2 Bryony Martin 2011
Peculiar velocitiesAdditional motions specific to individual galaxies
• Recession velocity due to Hubble flow
• Peculiar velocity due to matter distribution of local environment
– baryonic and dark matter
Recession velocity
Peculiar velocity
Overdensity
LINE OF SIGHT
radial
transverse
Peculiar Velocities in Supernova Cosmology3 Bryony Martin 2011
Type Ia supernovaeThe standard candles of the universe
Kim, et al. 1997
Peculiar Velocities in Supernova Cosmology4 Bryony Martin 2011
Supernova cosmologyCalculating constraints on cosmological parameters
Kessler, et al. 2009Kessler, et al. 2009
Peculiar Velocities in Supernova Cosmology5 Bryony Martin 2011
Supernova cosmology with peculiar velocitiesPeculiar velocities induce Doppler effects in supernova observations
Kessler, et al. 2009Doppler shifting
Peculiar Velocities in Supernova Cosmology6 Bryony Martin 2011
Supernova cosmology with peculiar velocitiesPeculiar velocities induce Doppler effects in supernova observations
Kessler, et al. 2009Doppler shifting
Inaccurate best-fit cosmology
INACCURATE PARAMETER
CONSTRAINTS
Peculiar Velocities in Supernova Cosmology7 Bryony Martin 2011
Simulation dataSimulated galaxies with explicit velocity information
Kitzbichler & White, 2007
www.mpa-garching.mpg.de
Peculiar Velocities in Supernova Cosmology8 Bryony Martin 2011
Simulated galaxiesMock survey galaxy catalogues showing structure
Peculiar Velocities in Supernova Cosmology9 Bryony Martin 2011
Supernova ratesUsing galaxy properties to predict the presence of type Ia supernovae
Mannucci et al, 2005
Peculiar Velocities in Supernova Cosmology10 Bryony Martin 2011
Simulated Type Ia SupernovaeSupernova dataset with known peculiar velocities
Peculiar Velocities in Supernova Cosmology11 Bryony Martin 2011
Hubble diagramConstructed using simulated supernova data
Peculiar Velocities in Supernova Cosmology12 Bryony Martin 2011
Shifts in Ωm for various maximum redshifts
Average shifts in Ωm are within 1σ
Peculiar Velocities in Supernova Cosmology13 Bryony Martin 2011
Shifts in H0 for various maximum redshifts
Average shifts in H0 are ~1σ
Peculiar Velocities in Supernova Cosmology14 Bryony Martin 2011
Calculated values of Ωm using true and observed redshifts
Calculated values are 1-2σ from the fiducial value of Ωm
Peculiar Velocities in Supernova Cosmology15 Bryony Martin 2011
Calculated values of H0 using true and observed redshifts
Calculated values using observed redshifts are 2σ less than the fiducial value of H0
Peculiar Velocities in Supernova Cosmology16 Bryony Martin 2011
Summary
RESULTS Simulated type Ia supernova dataset with peculiar velocity information
• Parameter estimates from simulated Hubble diagrams using both cosmological and observed redshifts
• Measured shifts in parameters which are roughly of the order of 1σ
