Responsibilities

• 203-1-3461 General Astronomy 1 (Lecturer), 2025A

Education

• 2025- now, PhD Title is not available
  with Adi Zitrin
• 2023- 2025, MSc Transient sources in galaxy cluster fields: Prospects for different gravitationally lensed transients
  with Adi Zitrin

  Abstract/Description: Strong gravitational lensing of transient sources has spurred much interest in recent years. It can teach us about the lensed sources themselves, the composition of the lens (and mainly its dark component), and the expansion rate of the universe through time delays. This thesis is based on three individual papers examining various aspects related to transient sources in galaxy clusters. Each paper is discussed shortly in a separate chapter and the published papers are attached in the appendix. Since massive galaxy clusters act as gravitational lenses, strong-lensing mass modeling is a crucial part for studying objects in lensing galaxy clusters, including transient sources. Hence, in the first chapter, the work begins with a strong lensing mass model for the first galaxy cluster imaged with the James Webb Space Telescope (JWST), SMACS J0723.3-7327. We identify several multiply imaged systems that are then used as constraints, and for the majority of which the redshift is measured here spectroscopically for the first time. The Light-Traces-Mass lens modeling method is then used to obtain the dark matter mass distribution in the cluster. This work was done on data obtained with the Hubble-Space-Telescope (HST) in preparation for the first public release of JWST images. In the second chapter, an extensive search for transients was conducted in a sample of 41 galaxy clusters from the RELICS HST survey (including SMACS J0723.3-7327). The main motivation was to look for caustic crossing events (CCEs) of distant stars which, following the brightness of the first CCE ever detected, could be bright enough to detect in this survey. No CCEs were found over all 41 clusters, which supplied important empirical bounds for the rate of CCEs in galaxy cluster fields to typical HST magnitudes. Nonetheless, the search led to the detection of 6 supernova candidates, three of them being new discoveries presented and classified in this work for the first time. The observed ratio of core-collapse to Type Ia supernovae is discussed. The third chapter considers
  a yet another type of varying sources that might be lensed by galaxy clusters – Type I active galactic nuclei (AGN) (and quasars). In this work it is suggested that gravitational time delays between multiple images of strongly lensed quasars may be leveraged to conduct Reverberation Mapping at high redshift on a feasible time scale. The work supplies a detailed estimate of the number of both high-mass (∼ 109 − 1010 M⊙), and high-redshift (z ≳ 4 − 12) quasars – including the recently discovered Little Red Dot population – that are expected to be strongly lensed by clusters and discovereable with different observing facilities. Together, these chapters provide a glimpse into the diversity of scientific insights that are achievable with the study of strongly lensed transient sources in galaxy clusters.