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Tests for systematic effects in supernova cosmology
Stockholm University, Faculty of Science, Department of Physics.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Type~Ia supernovae are used as standard candles to measure the energy density components of the universe. This led to the new paradigm in cosmology: only about 30\% of the universe is made by ordinary pressure-less matter, the rest is associated with an unknown form of energy with a negative equation of state parameter, called dark energy, able to drive the accelaration of the universe. The importance of this discovery requires to fully understand and control the possible systematic effects affecting both current and future measurements, aiming at probing the equation of state parameter, i.e. the nature of dark energy.

In this thesis, we tackle systematic effects involved in several aspects of supernova cosmology. Studies of supernova colours are used for investigating the homogeneity of the standard candle and to improve the spectral templates used for $K$-corrections. We have measured the intrinsic colour dispersion and assessed its correlation between different epochs of supernova evolution. We develop a technique for fitting the $I$-band ligthcurve and present studies of correlations of its properties with the SN luminosity. Moreover, we present a pioneer study of restframe $I$-band Hubble diagram extended at redshift $\sim$ 0.5. This is found to be a valuable complementary tool for cosmological studies, and the results found are consistent with the concordance model of the universe, though the uncertainties are large. Presence of grey dust in the intergalactic medium is investigated both using the $I$-band Hubble diagram and supernova colour excess. Although the low statistics of the high redshift sample used do not allow to draw firm conclusions, both methods are tested and shown to be useful for probing the presence of intergalactic dust. The hypothesis of supernova population drift is tested in two different ways, both studying restframe $I$-band lightcurve properties and by comparing spectra of high redshift with those of nearby SNe. One distant supernova SN~2002fd (z=0.279) shows spectral similarities with 1991T/1999aa like objects. No signs of evolution in supernova properties is found in these studies, strengthening our confidence in the measured cosmological parameters.

Place, publisher, year, edition, pages
Stockholm: Fysikum , 2004. , 14 p.
Series
SICS dissertation series, ISSN 1101-1335 ; 47
Keyword [en]
Cosmology, supernovae, astrophysics
Identifiers
URN: urn:nbn:se:su:diva-73ISBN: 91-7265-455-4 (print)OAI: oai:DiVA.org:su-73DiVA: diva2:198015
Public defence
2004-04-02, sal FB53, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-03-11 Created: 2004-03-11Bibliographically approved
List of papers
1. Restframe I-band Hubble diagram for Type Ia supernovae up to Z ~ 0.5
Open this publication in new window or tab >>Restframe I-band Hubble diagram for Type Ia supernovae up to Z ~ 0.5
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-24652 (URN)
Note
Part of urn:nbn:se:su:diva-73Available from: 2004-03-11 Created: 2004-03-11 Last updated: 2010-01-13Bibliographically approved
2. The intrinsic colour dispersion in Type Ia supernovae
Open this publication in new window or tab >>The intrinsic colour dispersion in Type Ia supernovae
2003 In: Astronomy and Astrophysics, ISSN 0004-6361, Vol. 404, no 3, 901-912 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24653 (URN)
Note
Part of urn:nbn:se:su:diva-73Available from: 2004-03-11 Created: 2004-03-11Bibliographically approved
3. Search for spectral evolution in high-redshift Type Ia supernovae: evidence for SN 1991T/SN1999aa-like object at z=0.279
Open this publication in new window or tab >>Search for spectral evolution in high-redshift Type Ia supernovae: evidence for SN 1991T/SN1999aa-like object at z=0.279
Show others...
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-24654 (URN)
Note
Part of urn:nbn:se:su:diva-73Available from: 2004-03-11 Created: 2004-03-11 Last updated: 2010-01-13Bibliographically approved
4. The Nearby Supernova Cosmology Project Spectroscopic Follow-up: Uncertainty Estimation for Quantitative Studies
Open this publication in new window or tab >>The Nearby Supernova Cosmology Project Spectroscopic Follow-up: Uncertainty Estimation for Quantitative Studies
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-24655 (URN)
Note
Part of urn:nbn:se:su:diva-73Available from: 2004-03-11 Created: 2004-03-11 Last updated: 2010-01-13Bibliographically approved

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