Projects / Programmes
Unveiling the expansion of the Universe with strongly lensed supernovae
| Code |
Science |
Field |
Subfield |
| 1.02.03 |
Natural sciences and mathematics |
Physics |
Astronomy |
| Code |
Science |
Field |
| P007 |
Natural sciences and mathematics |
Astronomy |
Cosmological parameters, Hubble constant, galaxy clusters, strong lensing, supernovae
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
51012 |
PhD Tanja Petrushevska |
Physics |
Head |
2019 - 2022 |
0 |
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
1540 |
University of Nova Gorica |
Nova Gorica |
5920884000 |
0 |
Abstract
The Hubble constant (H0) is a fundamental cosmological parameter that can inform us about the most important scales in the Universe: its size, age, expansion rate, and critical density. To accurately determine H0 has thus been a major focus in observational cosmology and astrophysics over the past 90 years. Recent years have, however, seen a re-emergence of an inconsistency between the value of Hubble constant inferred from the scales set by the universe at early epochs and the value derived from the local distance scale. To clarify this situation, the results of additional independent and high-precision techniques, which rely on different physics, are of key importance.
Large Synoptic Survey Telescope (LSST) currently is being built in Chile, will see the first light in 2021, and full operations for a ten-year survey will start in January 2022. The LSST will be a ground-based survey with an 8.4-meter telescope aimed to continuously scan the sky in search for transient explosions. Providing cutting-edge constraints on the cosmological parameters is one of the key science goals of LSST. Our group at the University of Nova Gorica has recently joined the LSST collaboration. This enables the full access to preparatory LSST data such as simulated observing strategies and catalogues. Once the LSST starts running, we will have full access to the images and catalogues.
The objective of the proposed project is twofold: the first is to provide an independent way to measure the Hubble constant with the LSST data. In particular, we will achieve this by using strongly lensed supernovae by galaxy clusters with measured time delays between the multiple supernova images. The second objective of the proposed project is to investigate the effect of weak lensing on supernova cosmology that will be done with the LSST data. All the codes and results that will be produced in these five work packages will be developed and tested on the simulated LSST, and on the real data once the LSST sees the first light. With these two objectives, we plan to contribute to the LSST cosmology tasks and the overall success of LSST, which will be the leading telescope survey in the next decade.
Significance for science
In the short term of the duration of the project, we will provide forecasts of strongly lensed supernova yields and properties before the advent of LSST and JWST. Therefore, our results will show the prospects of detecting strongly lensed supernovae in the massive galaxy clusters fields in LSST data. Motivated by our previous experience with cluster searches and iPTF16geu, we are opening a new window to study cosmology and astrophysics with strongly-lensed supernovae. We will investigate the LSST optimal observing strategy for strongly lensed supernovae in reference to the LSST white paper call. We will also determine the methods to filter out strongly lensed supernovae from the avalanche of LSST transient data alerts. Beyond the LSST survey data, we will explore the need both spectroscopic and high resolution imaging data to enable high precision time delay distance and compound lens distance ratio measurements. We anticipate that using only the LSST for time-delay cosmography will strongly benefit from follow-up observations from other instruments. Therefore, we will explore synergies with existing and upcoming facilities as the JWST, so simulation work to prepare for these proposals will be also needed.
In the long term, the planned research that we are proposing here will directly contribute to solving recent discrepancy of how fast the Universe is expanding. A sample of strongly lensed supernovae, especially supernovae Ia, will be a powerful resource for cosmological studies. Furthermore, the standard-candle nature of supernovae Ia also provides extra constraining power on the mass distribution of the lens cluster, which holds important clues to galaxy formation and evolution. The standard candle property allows the flux magnification to be estimated directly, independent of any model related to the lensing cluster. This removes important degeneracies in gravitational lensing measurements, the mass-sheet degeneracy and the source-plane degeneracy. The magnification boost provided by the cluster lenses enhances the possibility of observing supernovae at unprecedented distances, that otherwise would be undetectable. This enables to study their properties and their possible evolution over redshift. Furthermore, discoveries of distant supernovae can be used to pinpoint the supernova rates at very high distances where they are poorly measured.
Measuring cosmological parameters from the supernovae Ia data is one of the priority of the LSST. The effect of weak lensing adds an additional uncertainty to using supernovae Ia as cosmological standard candles at high redshift. In previous works by other authors, similar attempts have been made to estimate the gravitational lensing effects on supernova cosmology. However, this has never been estimated for the specific LSST simulated supernova dataset which will extend to high redshift.
With these objectives, we plan to contribute to the DESC cosmology tasks and the overall success of LSST, which will be the leading telescope survey in the next decade.
Significance for the country
In the short term of the duration of the project, we will provide forecasts of strongly lensed supernova yields and properties before the advent of LSST and JWST. Therefore, our results will show the prospects of detecting strongly lensed supernovae in the massive galaxy clusters fields in LSST data. Motivated by our previous experience with cluster searches and iPTF16geu, we are opening a new window to study cosmology and astrophysics with strongly-lensed supernovae. We will investigate the LSST optimal observing strategy for strongly lensed supernovae in reference to the LSST white paper call. We will also determine the methods to filter out strongly lensed supernovae from the avalanche of LSST transient data alerts. Beyond the LSST survey data, we will explore the need both spectroscopic and high resolution imaging data to enable high precision time delay distance and compound lens distance ratio measurements. We anticipate that using only the LSST for time-delay cosmography will strongly benefit from follow-up observations from other instruments. Therefore, we will explore synergies with existing and upcoming facilities as the JWST, so simulation work to prepare for these proposals will be also needed.
In the long term, the planned research that we are proposing here will directly contribute to solving recent discrepancy of how fast the Universe is expanding. A sample of strongly lensed supernovae, especially supernovae Ia, will be a powerful resource for cosmological studies. Furthermore, the standard-candle nature of supernovae Ia also provides extra constraining power on the mass distribution of the lens cluster, which holds important clues to galaxy formation and evolution. The standard candle property allows the flux magnification to be estimated directly, independent of any model related to the lensing cluster. This removes important degeneracies in gravitational lensing measurements, the mass-sheet degeneracy and the source-plane degeneracy. The magnification boost provided by the cluster lenses enhances the possibility of observing supernovae at unprecedented distances, that otherwise would be undetectable. This enables to study their properties and their possible evolution over redshift. Furthermore, discoveries of distant supernovae can be used to pinpoint the supernova rates at very high distances where they are poorly measured.
Measuring cosmological parameters from the supernovae Ia data is one of the priority of the LSST. The effect of weak lensing adds an additional uncertainty to using supernovae Ia as cosmological standard candles at high redshift. In previous works by other authors, similar attempts have been made to estimate the gravitational lensing effects on supernova cosmology. However, this has never been estimated for the specific LSST simulated supernova dataset which will extend to high redshift.
With these objectives, we plan to contribute to the DESC cosmology tasks and the overall success of LSST, which will be the leading telescope survey in the next decade.
