How the StarDICE photometric calibration of standard stars can improve cosmological constraints?

TL;DR

The paper discusses how the StarDICE calibration method, based on NIST standards, can significantly improve the precision of supernova flux calibration, thereby reducing biases in dark energy measurements.

Contribution

It introduces the StarDICE experiment as a new calibration approach that relies on NIST-based observations to achieve sub-percent photometric accuracy.

Findings

Calibration errors can bias cosmological parameters.

StarDICE can recalibrate the CALSPEC catalog at millimagnitude precision.

The method improves flux calibration accuracy for supernova observations.

Abstract

The number of type Ia supernova (SNe Ia) observations will grow significantly within the next decade, mainly thanks to the Legacy Survey of Space and Time (LSST) undertaken by the Vera Rubin Observatory in Chile. With this improvement, statistical uncertainties will decrease, and flux calibration will become the main uncertainty for the characterization of dark energy. Currently, the astronomical flux scale is anchored on the numerical models of white dwarf atmospheres from the CALSPEC catalog, and every error on the model can induce a bias over cosmological parameters inference. The StarDICE experiment proposes a new calibration reference that only relies on observations from the optical watt defined by the NIST towards the magnitude of standard stars. It is currently operating at l'Observatoire de Haute-Provence and has been collecting data since the beginning of 2023. To overcome the photometric calibration uncertainty and reach a sub-percent precision, the instrument throughput has been calibrated with a Collimated Beam Projector. It will be monitored on-site with a LED-based artificial star source calibrated with NIST photodiodes. In this proceeding, we will first illustrate how an error in the photometric calibration can impact the SNe Ia distance moduli and thus bias the measurement of cosmological parameters. Then we will present the StarDICE experiment and how we can recalibrate the CALSPEC catalog at the millimagnitude level on the NIST scale with photometric analysis.