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Detection and identification of primordial objects
  Astronomy and astrophysics

Friday 23 January 2015
from 10:30 to 11:30
at FB52
Speaker : Claes-Erik Rydberg (SU)
Abstract : An introductory overview to the endeavour of detecting and identifying stars and galaxies in the pre-reionization (z > 6) universe is presented. Simulations indicate that the first Population III stars should appear in minihalos of mass 10^5 – 10^6 Msol at z ≈ 10-30. To assess the detectability of these objects, theoretical models of these stars and their surrounding HII regions are used. We assess the plausibility of detection with the upcoming James Webb Space Telescope (JWST), using the gravitational lensing provided by the galaxy cluster MACSJ0717.5+3745. The conclusion is that the detection of these objects is highly improbable but not impossible. To investigate the prospects of detecting and identifying the first galaxies we use the spectral synthesis code Yggdrasil. According to this code, JWST may be able to detect Population III galaxies with stellar masses as low as 10^5 Msol at z ≈ 10 in unlensed fields. Hubble Space Telescope (HST) and/or JWST broadband color criteria to single out Population III galaxy candidates are presented. Two Population III galaxy candidates are presented, discovered by fitting HST/CLASH data to Yggdrasil and comparison model grids. These two candidates are the first Population III galaxy candidates discovered at z > 6.5. A highly-magnified doubly lensed extremely high-redshift (z ≈ 7.8) Lyα-emitter is also identified.

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