Peculiar Velocities in Supernova Cosmology Bryony Martin MSc, 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 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
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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
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Type Ia supernovaeThe standard candles of the universe
Kim, et al. 1997
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Supernova cosmologyCalculating constraints on cosmological parameters
Kessler, et al. 2009Kessler, et al. 2009
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Supernova cosmology with peculiar velocitiesPeculiar velocities induce Doppler effects in supernova observations
Kessler, et al. 2009Doppler shifting
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Supernova cosmology with peculiar velocitiesPeculiar velocities induce Doppler effects in supernova observations
Kessler, et al. 2009Doppler shifting
Inaccurate best-fit cosmology
INACCURATE PARAMETER
CONSTRAINTS
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Simulation dataSimulated galaxies with explicit velocity information
Kitzbichler & White, 2007
www.mpa-garching.mpg.de
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Simulated galaxiesMock survey galaxy catalogues showing structure
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Supernova ratesUsing galaxy properties to predict the presence of type Ia supernovae
Mannucci et al, 2005
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Simulated Type Ia SupernovaeSupernova dataset with known peculiar velocities
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Hubble diagramConstructed using simulated supernova data
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Shifts in Ωm for various maximum redshifts
Average shifts in Ωm are within 1σ
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Shifts in H0 for various maximum redshifts
Average shifts in H0 are ~1σ
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Calculated values of Ωm using true and observed redshifts
Calculated values are 1-2σ from the fiducial value of Ωm
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Calculated values of H0 using true and observed redshifts
Calculated values using observed redshifts are 2σ less than the fiducial value of H0
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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