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Properties of Type Ia Supernovae: From the (intermediate) Palomar Transient Factory
Stockholm University, Faculty of Science, Department of Physics.ORCID iD: 0000-0003-0783-3323
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Type Ia Supernovae (SNe) have been used to discover the accelerated expansion of the universe but many open questions remain unanswered. These include the stellar progenitor, extinction and possible systematic trends in the supernova brightness for different host galaxy environments or cosmic time. In this thesis we attempt to address these open questions by looking at a large homogeneous sample of nearby SNe from the Palomar Transient Factory (2009-2012) and the intermediate Palomar Transient Factory (2013-2017) for which we have 265 well-observed light-curves in the R-band and 2981 spectra from a total of 2060 SNe.

In Paper I we study the global properties of the R-band light-curves, such as rise-time, stretch and intrinsic brightness at different SN phases, to examine if there are multiple populations in any of the parameters suggesting different progenitor channels. We do not find evidence supporting this. We characterize the second maximum in the R-band in Paper II and find a correlation between the time from light-curve maximum, and the "colour-stretch" parameter, a proxy for 56Ni mass. We also found that the integrated flux under the second maximum, correlates with the transparency timescale, a proxy for total ejecta mass. Using these two relations we find that sub-Chandrasekhar double detonation models can account for the biggest fraction of the PTF/iPTF SNe light-curves properties. In Paper III we present the spectroscopic sample of PTF/iPTF and using automatic machine learning tools to explore spectral features and possible connection to photometric and host galaxy properties.

Paper IV focuses on a small sample of SNe, with multi-wavelength light-curves, to address one of the most important systematic uncertainties in supernova cosmology: extinction by dust in the line-of-sights. We found a diversity in the reddening laws as characterised by the total-to-selective extinction, RV. Finally, Paper V looks at a strongly lensed SNIa at z=1.4  to see if there is evolution of its spectral and photometric properties over cosmic time. Both Paper IV and Paper V use the code developed for Paper III to analyse spectra.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2019. , p. 73
Keywords [en]
Type Ia supernovae, cosmology, machine learning
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-167380ISBN: 978-91-7797-684-4 (print)ISBN: 978-91-7797-685-1 (electronic)OAI: oai:DiVA.org:su-167380DiVA, id: diva2:1300923
Public defence
2019-05-24, sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

Available from: 2019-04-29 Created: 2019-04-01 Last updated: 2019-04-17Bibliographically approved
List of papers
1. R-band light-curve properties of Type Ia supernovae from the (intermediate) Palomar Transient Factory
Open this publication in new window or tab >>R-band light-curve properties of Type Ia supernovae from the (intermediate) Palomar Transient Factory
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 483, p. 5045-5076Article in journal (Refereed) Published
Abstract [en]

We present the best 265 sampled R-band light curves of spectroscopically identified Type Ia supernovae (SNe) from the Palomar Transient Factory (PTF; 2009-2012) survey and the intermediate Palomar Transient Factory (iPTF; 2013-2017). A model-independent light-curve template is built from our data-set with the purpose to investigate average properties and diversity in our sample. We searched for multiple populations in the light-curve properties using machine learning tools. We also utilized the long history of our light curves, up to 4000 days, to exclude any significant pre- or post- supernova flares. From the shapes of light curves we found the average rise time in the R band to be 16.8&#x2212;0.6+0.5'>16.8 +0.5 −0.6  16.8−0.6+0.5 days. Although PTF/iPTF were single-band surveys, by modelling the residuals of the SNe in the Hubble–Lemaître diagram, we estimate the average colour excess of our sample to be 〈E(BV)〉 ≈ 0.05(2) mag and thus the mean corrected peak brightness to be MR = −19.02 ± 0.02 +5log&#x2061;(H0[kms&#x2212;1Mpc&#x2212;1]/70)'>+5log(H 0 [kms −1 Mpc −1 ]/70) +5log⁡(H0[kms−1Mpc−1]/70) mag with only weak dependennce on light–curve shape. The intrinsic scatter is found to be σR = 0.186 ± 0.033 mag for the redshift range 0.05 < z < 0.1, without colour corrections of individual SNe. Our analysis shows that Malmquist bias becomes very significant at z = 0.13. A similar limitation is expected for the ongoing Zwicky Transient Facility (ZTF) survey using the same telescope, but new camera expressly designed for ZTF.

Keywords
supernovae: general, cosmology: observations
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-167376 (URN)10.1093/mnras/sty3301 (DOI)000462281900058 ()
Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-05-22Bibliographically approved
2. Characterizing the secondary maximum in the r-band for Type Ia supernovae: diagnostic for the ejecta mass
Open this publication in new window or tab >>Characterizing the secondary maximum in the r-band for Type Ia supernovae: diagnostic for the ejecta mass
2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, no 2, p. 2343-2354Article in journal (Refereed) Published
Abstract [en]

An increase in the number of studied Type Ia supernovae (SNe Ia) has demonstrated that this class of explosions has a greater diversity in its observables than was previously assumed. The reasons (e.g. the explosion mechanism, progenitor system) for such a diversity remain unknown. Here, we analyse a sample of r-band light curves of SNe Ia, focusing on their behaviour similar to 2-4 weeks after maximum light, i.e. the second maximum. We characterize the second maximum by its timing (t(r2)) and the integrated flux ((F) over bar (r2)). We find that t(r2) correlates with the 'colour-stretch' parameter s(BV), which can be used as a proxy for Ni-56 mass, and (F) over bar (r2) correlates with the transparency time-scale, t(0). Using (F) over bar (r2) for a sample of 199 SNe from the Palomar Transient Factory and intermediate Palomar Transient Factory, we evaluate a distribution on t(0) for a sample of SNe Ia found in an 'untargeted' survey. Comparing this distribution to the predictions of t(0) ranges from models we find that the largest overlap in t(0) values between models and observations is for the sub-Chandrasekhar double detonation models. We also compare our relations between t(0) and (F) over bar (r2) with that from the 1D explosion models of Goldstein & Kasen and confirm that (F) over bar (r2) can be used as a diagnostic of the total ejecta mass.

Keywords
supernovae: general
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-167378 (URN)10.1093/mnras/stz493 (DOI)000474886200062 ()
Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-08-19Bibliographically approved
3. Spectroscopic properties of type Ia Supernovae from the (intermediate) Palomar Transient Factory
Open this publication in new window or tab >>Spectroscopic properties of type Ia Supernovae from the (intermediate) Palomar Transient Factory
(English)Manuscript (preprint) (Other academic)
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-167379 (URN)
Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-04-01Bibliographically approved
4. Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 mu m
Open this publication in new window or tab >>Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 mu m
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2015 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 453, no 3, p. 3300-3328Article in journal (Refereed) Published
Abstract [en]

We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2-2 mu m. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B - V) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction R-V. In particular, we note that for the two SNe with E(B - V) greater than or similar to 1 mag, for which the colour excess is dominated by dust extinction, we find R-V = 1.4 +/- 0.1 and R-V = 2.8 +/- 0.1. Adding UV photometry reduces the uncertainty of fitted R-V by similar to 50 per cent allowing us to also measure R-V of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe.

Keywords
circumstellar matter, supernovae: general, supernovae: individual: SNe 2012cg, supernovae: individual: 2012cu, dust, extinction
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-123790 (URN)10.1093/mnras/stv1505 (DOI)000363649000085 ()
Available from: 2016-06-30 Created: 2015-12-07 Last updated: 2019-04-01Bibliographically approved
5. Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at z=1.4
Open this publication in new window or tab >>Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at z=1.4
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2017 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 603, article id A136Article in journal (Refereed) Published
Abstract [en]

Context. The light from distant supernovae (SNe) can be magnified through gravitational lensing when a foreground galaxy is located along the line of sight. This line-up allows for detailed studies of SNe at high redshift that otherwise would not be possible. Spectroscopic observations of lensed high-redshift Type Ia supernovae (SNe Ia) are of particular interest since they can be used to test for evolution of their intrinsic properties. The use of SNe Ia for probing the cosmic expansion history has proven to be an extremely powerful method for measuring cosmological parameters. However, if systematic redshift-dependent properties are found, their usefulness for future surveys could be challenged. Aims. We investigate whether the spectroscopic properties of the strongly lensed and very distant SN Ia PS1-10afx at z = 1.4, deviates from the well-studied populations of normal SNe Ia at nearby or intermediate distance. Methods. We created median spectra from nearby and intermediate-redshift spectroscopically normal SNe Ia from the literature at -5 and + 1 days from light-curve maximum. We then compared these median spectra to those of PS1-10afx. Results. We do not find signs of spectral evolution in PS1-10afx. The observed deviation between PS1-10afx and the median templates are within what is found for SNe at low and intermediate redshift. There is a noticeable broad feature centred at lambda similar to 3500 angstrom which is present only to a lesser extent in individual low-and intermediate-redshift SN Ia spectra. From a comparison with a recently developed explosion model, we find this feature to be dominated by iron peak elements, in particular, singly ionized cobalt and chromium.

Keywords
supernovae: individual: PS1-10afx, gravitational lensing: strong, supernovae: general
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-147181 (URN)10.1051/0004-6361/201730989 (DOI)000406619100143 ()
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2019-04-01Bibliographically approved

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