Dark Energy and the Impact of Lensed Distance Indicators
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Presently, our Universe is dominated by dark energy, which acts like a repulsive force and makes the Universe expand at an accelerating rate. Einstein's cosmological constant, associated with the energy of the vacuum, is a hypothesis for the dark energy which has passed all tests so far. One of the major goals of cosmology today is to prove or falsify this hypothesis.
Standard candles, such as Type Ia supernovae (SNe), all have nearly the same intrinsic brightness and can therefore be used as distance indicators. From the distance-redshift relation, the nature of dark energy can be deduced. In this thesis, a parameterization of the evolution of dark energy with time, based on a truncated power series, is investigated and scrutinized.
Light rays can be deflected, i.e. gravitationally lensed, by matter between the source and the observer. Gravitational lensing can lead to amplification or de-amplification of the flux, which increases the scatter in the observed brightness for standard candles. Simulations presented here, show that it should be possible to estimate the amount of gravitational magnification of point sources using the information from observed galaxies along the line of sight to model the matter in the foreground. The estimated lensing magnifications of a set of Type Ia SNe observed within the Great Observatories Origins Deep Survey (GOODS) are presented here. For a subsample of GOODS Type Ia SNe with accurately measured magnitudes, there is a correlation between observed brightness and estimated magnification at the 90% confidence level. Not only SNe are affected by gravitational lensing, but also other distance indicators. This thesis also discusses the impact of gravitational lensing on the cosmological results which could be obtained from high redshift standard sirens, the gravitational wave analog of electromagnetic standard candles.
Place, publisher, year, edition, pages
Stockholm: Fysikum , 2007.
Research subject Physics
IdentifiersURN: urn:nbn:se:su:diva-6842ISBN: 978-91-7155-449-9OAI: oai:DiVA.org:su-6842DiVA: diva2:197179
2007-06-08, sal FB53, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:15
Mellier, Yannick, Dr
Goobar, Ariel, Professor