Master Thesis Defense by Luka Vujeva

Title: Finding the most efficient survey design for discovering high-redshift galaxies with JWST

Abstract: The James Webb Space Telescope (JWST) is the first telescope capable of probing the creation of the earliest galaxies in the Universe. Several large blank field observing programs aimed at combating the effects of cosmic variance at high redshifts such as JADES and CEERS have been unsuccessful in probing the critical 15 < z < 20 regime in which the first galaxies are believed to have formed. This has motivated the search for a survey strategy that will be able to effectively probe this redshift regime. This work analyzes the use of gravitationally lensed fields, which has historically been the most effective discovery tool with the Hubble Space Telescope (HST), utilizing the 6 galaxy clusters which provided the highest median magnification factor within a single JWST NIRCam pointing (2.1'x2.1') in order to suppress the effects of cosmic variance at high redshift. Testing was conducted using the magnification maps of archival models of the 6 clusters selected from the CLASH/MUSES catalogues, modelled using both HST and JWST data, and simulated massive elliptical galaxies created using LENSTOOL. The lens models were used in combination with mock survey code which employs the use of a luminosity function extrapolated into the z > 8 regime in conjunction with a cosmic variance calculator cosmic-variance in order to estimate both the expected number of galaxies as a function of redshift and the highest redshift galaxy one would expect to see in a given survey strategy. These results were then compared against the results of large area, blank field surveys such as JADES and CEERS in order to determine the most effective survey strategy for JWST. We found that the fields containing massive foreground galaxy clusters specifically chosen to have the highest median magnification factor within the NIRCam pointing provide the highest probability of both probing the 15 < z < 20 regime, as well as discovering the highest redshift galaxy possible with JWST. Such a survey strategy would also be significantly more time effective given the fewer lines of sight required to discover these ultra-high redshift galaxies.

Supervisor:

  • Charles Louis Steinhardt, University of Copenhagen, Niels Bohr Insitute

Censor:

  • Hans Kjeldsen, Aarhus University