MS: Fatimah Raihan & Monthly Discussion

/MS: Fatimah Raihan & Monthly Discussion

MS: Fatimah Raihan & Monthly Discussion

Event Details

Title: Update on my project: Testing 3D-HST photo-zs for weak lensing studies

Accurate weak lensing mass estimates are needed in order to calibrate mass proxies for the cosmological exploitation of galaxy cluster surveys. Such measurements require accurate knowledge
of the redshift distribution of the weak lensing source galaxies. In this context, we investigate the accuracy of photometric redshifts computed by the 3D-HST team for the CANDELS fields, which
provide a relevant photometric reference data set for deep weak lensing studies. Through the comparison to spectroscopic and photometric redshift estimates based on very deep data from the
Hubble Ultra Deep Field, we identify catastrophic redshift outliers in the 3D-HST/CANDELS catalogue. These would significantly bias weak lensing results if not accounted for. We investigate
the cause of these outliers and demonstrate that modifications to the Bayesian redshift probability prior and also selecting the appropriate photometric bands can reduce the net impact for weak lensing studies.