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Supernovae under the gravitational lens
Stockholm University, Faculty of Science, Department of Physics.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With general relativity as its foundation, the Standard Model of Cosmology has been developed, a model in which all matter is homogeneously and isotropically distributed throughout the Universe. We know for sure that this is not true since inhomogeneous structures such as galaxies, planets and synthesizers, are known to exist on small cosmological scales. However, on large scales the approximation of homogeneity is very good. Despite this, inhomogeneities such as galaxies or clusters of galaxies, will affect the propagation of light in the Universe by bending the paths of light-rays according to the laws of general relativity. The phenomenon is known as gravitational lensing. The bending of light-rays is similar to what happens in an optical lens, where an image of an object may be distorted or (de-)magnified depending on the shape of the lens.

Using the magnifying power of a gravitational lens it is possible to see further out in the Universe, it is used as a natural gravitational telescope. Under the right circumstances this can be something very useful. By studying light from supernovae, exploding stars, it is to some extent possible to gather information on the constituents of our universe. If for some reason this light is affected on its way to us, e.g. by gravitational lensing, we are mislead into drawing erroneous conclusions unless the lensing effects are under control and corrected for. Trying to control this and other systematic uncertainties is a big challenge in supernova cosmology and is also becoming more and more important as statistical errors are being beaten down to very low levels.

Place, publisher, year, edition, pages
Stockholm: Fysikum , 2005. , 70 p.
Keyword [en]
Cosmology
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-638ISBN: 91-7155-107-7 (print)OAI: oai:DiVA.org:su-638DiVA: diva2:196414
Public defence
2005-09-30, sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Available from: 2005-09-03 Created: 2005-09-03Bibliographically approved
List of papers
1. Gravitational lensing of the farthest known supernova SN1997ff
Open this publication in new window or tab >>Gravitational lensing of the farthest known supernova SN1997ff
2001 In: The Astrophysical Journal, Vol. 561, no 106, 106-110 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24014 (URN)
Note
Part of urn:nbn:se:su:diva-638Available from: 2005-09-03 Created: 2005-09-03Bibliographically approved
2. Massive galaxy clusters as gravitational telescopes for distant supernovae
Open this publication in new window or tab >>Massive galaxy clusters as gravitational telescopes for distant supernovae
2003 In: Astronomy & Astrophysics, Vol. 405, 859-866 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24015 (URN)
Note
Part of urn:nbn:se:su:diva-638Available from: 2005-09-03 Created: 2005-09-03Bibliographically approved
3. Q-LET - quick lensing estimation tool: an application to SN2003es
Open this publication in new window or tab >>Q-LET - quick lensing estimation tool: an application to SN2003es
2004 In: Journal of Cosmology and Astroparticle Physics, Vol. 0403, no 002Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24016 (URN)
Note
Part of urn:nbn:se:su:diva-638Available from: 2005-09-03 Created: 2005-09-03Bibliographically approved
4. Corrections for gravitational lensing of supernovae: better than average?
Open this publication in new window or tab >>Corrections for gravitational lensing of supernovae: better than average?
Show others...
2006 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 640, 417-427 p.Article in journal (Refereed) Published
Abstract [en]

We investigate the possibility of correcting for magnification due to gravitational lensing of standard candlesources, such as Type Ia supernovae. Our method uses the observed properties of the foreground galaxies along thelines of sight to each source, and the accuracy of the lensing correction depends on the quality and depth of theseobservations as well as the uncertainties in translating the observed luminosities to the matter distribution in thelensing galaxies. The current work is limited to cases in which the matter density is dominated by the individualgalaxy halos. However, it is straightforward to generalize the method to also include gravitational lensing fromcluster scale halos.We show that the dispersion due to lensing for a standard candle source at z ¼1:5 can be reducedfrom about 7% toP3%; i.e., the magnification correction is useful in reducing the scatter in the Type Ia Hubble diagram,especially at high redshifts where the required long exposure times make it hard to reach large statistics andthe dispersion due to lensing becomes comparable to the intrinsic Type Ia scatter.

Place, publisher, year, edition, pages
The American Astronomical Society, 2006
Keyword
gravitational lensing — supernovae: general
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-24017 (URN)10.1086/499346 (DOI)
Note
Part of urn:nbn:se:su:diva-638Available from: 2005-09-03 Created: 2005-09-03 Last updated: 2017-12-13Bibliographically approved
5. Lensing magnification of supernovae in the GOODS-fields
Open this publication in new window or tab >>Lensing magnification of supernovae in the GOODS-fields
Show others...
2006 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 639, no 2, 991-998 p.Article in journal (Refereed) Published
Abstract [en]

Gravitational lensing of high-redshift supernovae is potentially an important source of uncertainty when cosmological parameters are being derived from the measured brightness of Type Ia supernovae, especially in deep surveys with scarce statistics. Photometric and spectroscopic measurements of foreground galaxies along the lines of sight of 33 supernovae discovered with the Hubble Space Telescope, both core-collapse and Type Ia, are used to model the magnification probability distributions of the sources. Modelling galaxy halos with SIS or NFW profiles and using M/L scaling laws provided by the Faber-Jackson and Tully-Fisher relations, we find clear evidence for supernovae with lensing (de)magnification. However, the magnification distribution of the Type Ia supernovae used to determine cosmological distances matches very well the expectations for an unbiased sample; i.e., their mean magnification factor is consistent with unity. Our results show that the lensing distortions of the supernova brightness can be well understood for the GOODS sample and that correcting for this effect has a negligible impact on the derived cosmological parameters.

Keyword
gravitational lensing, supernovae, general
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-24018 (URN)10.1086/499396 (DOI)
Available from: 2005-09-03 Created: 2005-09-03 Last updated: 2017-12-13Bibliographically approved

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