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Spectral properties of Type Ia supernovae up to z~0.3
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). (CoPS)
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
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2011 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 526, A119- p.Article in journal (Refereed) Published
Abstract [en]

Aims: Spectroscopic observations of type Ia supernovae obtained at the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT), in conjunction with the SDSS-II Supernova Survey, are analysed. We use spectral indicators measured up to a month after the lightcurve peak luminosity to characterise the supernova properties, and examine these for potential correlations with host galaxy type, lightcurve shape, colour excess, and redshift.

Methods: Our analysis is based on 89 type Ia supernovae at a redshift interval z = 0.05-0.3, for which multiband SDSS photometry is available. A lower-z spectroscopy reference sample was used for comparisons over cosmic time. We present measurements of time series of pseudo equivalent widths and line velocities of the main spectral features in type Ia supernovae.

Results: Supernovae with shallower features are found predominantly among the intrinsically brighter slow declining supernovae. We detect the strongest correlation between lightcurve stretch and the Si ii λ4000 absorption feature, which also correlates with the estimated mass and star formation rate of the host galaxy. We also report a tentative correlation between colour excess and spectral properties. If confirmed, this would suggest that moderate reddening of type Ia supernovae is dominated by effects in the explosion or its immediate environment, as opposed to extinction by interstellar dust.

Place, publisher, year, edition, pages
2011. Vol. 526, A119- p.
Keyword [en]
methods: data analysis, techniques: spectroscopic, supernovae: general, cosmology: observations, line: profiles
National Category
Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
Research subject
Physics; Astronomy
Identifiers
URN: urn:nbn:se:su:diva-56783DOI: 10.1051/0004-6361/201015705ISI: 000286458400131OAI: oai:DiVA.org:su-56783DiVA: diva2:413044
Available from: 2011-04-27 Created: 2011-04-27 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Spectral Properties of Type Ia Supernovae and Implications for Cosmology
Open this publication in new window or tab >>Spectral Properties of Type Ia Supernovae and Implications for Cosmology
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Type Ia supernovae can, for a short period of time, reach the same brightness as an entire galaxy. They are responsible for the creation of a large fraction of all heavy elements and can be used, as standard candles, to prove that the expansion of the universe is accelerating. Yet, we do not fully understand them.

A basic picture where Type Ia supernovae are caused by thermonuclear explosions of white dwarfs is generally accepted, but the details are still debated. These unknowns propagate into systematic uncertainties in the estimates of cosmological parameters. A Monte Carlo framework, SMOCK, designed to model this error propagation, is presented. Evolution with time/distance and the nature of reddening are studied as the dominant astrophysical uncertainties.

Optical spectra of Type Ia supernovae contain a wealth of information regarding the nature of these events, and can be used both to understand supernovae and to limit the systematic uncertainties in cosmological parameter estimates. We have reduced spectra observed with the Nordic Optical Telescope and the New Technology Telescope in conjunction with the SDSS-II supernova survey, and compared spectral properties (pseudo-Equivalent Widths and line velocities) of this sample with local supernovae.We have further studied possible systematic difficulties in such comparisons between nearby and distant supernovae, caused by noise and host galaxy contamination.Taking such uncertainties into account, we find a tentative evolution in supernova properties with redshift, compatible with expected demographic changes. Correlations with light curve shape found by other studies are confirmed. A tentative correlation with light curve colour is also presented. The latter could indicate an intrinsic component of the observed reddening, i.e. independent of interstellar dust in the host galaxy.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2011. 81 p.
Keyword
cosmology, spectroscopy, supernovae
National Category
Physical Sciences Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-56785 (URN)978-91-7447-300-1 (ISBN)
Public defence
2011-05-27, lecture room FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
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Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Accepted. Available from: 2011-05-05 Created: 2011-04-27 Last updated: 2011-04-29Bibliographically approved

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Nordin, JakobÖstman, LindaGoobar, ArielAmanullah, RahmanSollerman, Jesper
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