Bonn 2020 – scientific programme

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GR: Fachverband Gravitation und Relativitätstheorie

GR 12: Cosmology

GR 12.6: Talk

Thursday, April 2, 2020, 15:15–15:30, H-HS IV

Systematic Bias in the Zwicky Transient Facility Photometric Calibration and Effects on Hubble Constant Measurement — •Simeon Reusch — DESY Zeuthen, Platanenallee 6, 15738 Zeuthen

I am investigating the photometric accuracy of the Zwicky Transient Facility (ZTF; an all-sky survey) to identify possible sources of systematic errors.

By analyzing data from June to September 2018 I was able to identify a systematic bias in the ZTF photometry which is correlated to the amount of scattered moonlight adding to the background. At full moon, 20.5 mag calibrator stars are estimated up to 400 mmag too bright and at new moon, up to 35 mmag too faint. As simulation shows, such a bias can affect supernova population studies in a systematic way. Studies like this are necessary starting points for the the precise and accurate measurement of the supernovae's distance moduli, which are needed to map the expansion history of the universe. A systematic bias thus directly affects precision measurements of the local Hubble constant. The method developed here could be employed to test the time stability of other optical instruments as well.